Belial's Comprehensive Guide to 7950s
Not actually AMD 7950s
Not actually AMD 7950s
Who is Belial?
I'm sick and tired of all the lame reviews out there, that say every single product is Great Quality!!A+!. I get frustrated when I look for computer components and all you can find is people giving glowing reviews of everything simply because it's the only thing they've used. I appreciate reviews when people really pick apart an item based on what is worse or better on it than it's competitors, what matters, and apples to apples comparisons. For example, so many GPU comparisons are useless because they'll test 825mhz@1.1v with 60% fan speed vs 950mhz@1.25v with 55% fan speed, and that drives me crazy. The problem is reviewers don't truly push components - I want to see GPU tests where they push all the cards to 1100mhz@1.3v with 100% fan speed, and they do it properly, such as use +50% power tune.
This guide was brought about by my own search for a 7950, and basically trying out a ton of crappy models before realizing almost all 7950s are 'crappy' when you get to it. The confusion is that the chip itself, is amazing. I've tried most of the 7950 models and have modded a few 7950s. I originally posted this to OCN.
Introduction
There's a LOT of confusion on 7950s, and a lot of misinformation and bad reviews. This is complicated by the fact that the 7950 itself, is a great chip, but the many 7950 models out there, are terrible. This is further complicated by the fact that there are multiple revisions of cards that are totally different cards - as in totally different PCBs, VRMs, memory, everything. So you got one guy saying X is a great card, and another saying it's crap, and then you'll have people say crappy hardware is great because like most people, you buy 1 graphics card every ~2-3 years and you don't know what anything else is like. For reference, you will see tons of people swear their MSI Twin Frozr IIIs are quiet and cool, when in reality they are terribly loud and poor coolers.
Now, call me crazy, but if I spend $300 on a card, I want to know exactly what I'm buying and how it compares to the other models.
What is the 7950?
The 7950 is a Tahiti based GPU from AMD. It's considered the best bang for the buck card right now, as a mid-upper range card. It's generally considered a better card than it's direct competitor, the Nvidia 660TI, and a better value than the slightly weaker 660 or slightly stronger 670. It's about 5-10% slower per clock than it's bigger brother, the 7970, but almost half the price (and OC 7950 > Stock 7970). It is no longer plagued by the driver issues that used to make the 660TI a better card practically, either, and is a great candidate for Crossfire.
This card is also highly in demand for GPGPU tasks like bitcoin mining, as the fastest single card save for the 7970 and newly released flagships. It doesn't quite have the best performance per watt, but it still does very well compared to the 5xxx series.
The card will play any AAA title on high graphics, ie your Bioshock 3, Farcry3, Crysis3, Skyrim, on 1080, but will struggle to maintain Ultra at 60fps+ sometimes (and really, that's just Crysis3 and Skyrim). It'll be complete overkill for any slightly older or less intensive titles, ie your Rockstar, Blizzard games, MMORPGs, MOBAs, RTS, usually by a factor of 200-400%, and your slightly older AAA titles (ie Crysis1). In those instances, save your money, there's plenty of great value mid-range cards like the GTX460/470, 650Ti Boost, 7770/7790, and 7850. Be aware that multiple monitors don't appreciably increase GPU load (unless you are game is multi-screen).
If you play at 1440p/1600p+ or use a 72hz/120hz monitor, then there's much more justification for the 7950 for any modern title. Otherwise, it's really just stupid overkill. And don't buy it to 'future proof', all it takes is new software to release to make slightly older cards just useless compared to newer, weaker cards, and that's happened many times, as well as developer trends away from higher graphics (ie, after Crysis1, developers shied away from intense graphics in order to not alienate consumers, and GPU requirements really didn't grow at all for a few years).
Overclocking 7950s is usually about hitting a sweet spot, where additional voltage does nothing, and can range from 1050-1250mhz, with most cards hitting around 1100mhz@~1.2v. VRAM clocks range from 1500-2000mhz@1.65v, depending almost entirely on what VRAM chips you have moreso than binning.
Be aware that all 7950 models use the same chip, and none of them are binned. You'll often see models sold as 'super overclock' - it's simply a factory overclock that's still far short of the chip's actual capabilities. It'd be exactly like if MSI took the i5 (capable of ~4.5-5ghz overclock), and sold it as the MSI EXTREME COoLR IIVMX with a slight price mark-up, an 'overclock' to 3.7ghz, and a different heatsink. This is generally true of all graphics card models, really.
Like any high-end card, it runs very hot - it's max temp is 80-90*C, and max voltage is ~1.3-1.4v, although good luck staying cool on such voltages, even on water. VRMs, like any VRM, max out around 90-100*C, and memory voltage at ~1.65v. On a stock clock profile of 925mhz@1.25v, it's commonplace to hit 80-90*C on any non-reference heatsink on a warm day inside a well ventilated case during a proper heat test or GPGPU run, and VRMs on certain models hitting 120C. I don't even want to think of a reference card's temps. This is true of all high end GPUs though.
On ASIC
ASIC figures have shown to have zero impact on a card's capabilities. It is supposed to be an indication of a card's electrical efficacy, but there has been zero evidence or trends to indicate it means anything. That said, even if ASIC did affect a card's overclocks by effectively requiring more voltage for same clock, you're talking a very small increase in voltage, when the chip binning itself is responsible for a huge variance in the overclock anyways. At worst it means nothing, and at best it is accountable for extremely little. There have been extremely high overclocks with 40-50 ASICs, and low overclocks on plenty of 90+ ASICs, and zero apparent trend to show it means anything either way.
What you want in a card and Why
Core Voltage
Pretty straightforward, you are usually limited to 1.25, 1.3, or 1.381, but this is still plenty of voltage. Realistically you won't really be able to mess with this much due to temps (unless you use water), but it's very worthwhile to reduce it for some users.
Memory Voltage
This allows far greater memory clocks, and doesn't add too much heat. This is really important for a 'best' 7950, especially for GPGPU work where it can add a good 20+ khash for scrypt for just 100mhz in RAM overclock. For gaming, it's not nearly as important as core clock, you'll see about 0-1fps gain per 100mhz overclock, depending on the game and larger resolutions.
Hynix RAM vs Elpidas
Hynix RAM can hit about ~1700-1800mhz overclocked, while Elpida usually plateaus around 1550-1650. Furthermore, Hynix is also much tighter, so clock for clock it's better. This is extremely important for GPGPU work where VRAM overclocks is actually significantly more important than core clocks. An extra 100mhz can yield a good 10-20+ hashrate.
There are 2 types of Elpida: 50F and 60F (on a memory chip it's kinda hard to tell between 5 and 6, but it's there). The model numbers are exact same except for 50F and 60F, which indicates 5ghz and 6ghz DDR, or 1250mhz vs 1500mhz. The 60F Elpidas can overclock about an extra 100mhz, to 1600-1700mhz. In all other regards, these 2 Elpidas are the same, and I'd like to update the guide to be clearer on which Elpida each card has.
Hynix
Elpida. Note you can tell this is 50F, though it's hard to read
PCB
7970PCB > 7950 Reference PCB > 7950 Cheapo PCB
Recently companies have been using a cheapo 7950 pcb made by chinese custom-PCB manufacturer Yeston (known of making cheaper versions of cards) that has a weaker power phase, LFPAK mosfets, is more prone to VRM blow-outs and coil whine, and has a much lower ASIC.
A 7970 PCB can help with better voltage regulation, but be aware that if you do GPGPU work, this will make the 7950 act like a 7970 - meaning you need to run intensity 13 and 2 gpu threads.... meaning much lower hash rates on scrypt work. If you use SHA256, this isn't as big an issue. If you are just a gamer or overclocker, you will prefer a 7970 PCB. No one wants a cheapo 7950 PCB, which is very common these days on the 'updated' cards.
VRM Quality
Different companies use different VRM companies. Just like with motherboards, higher quality VRMs produce less heat, meaning less heat to the core due to the ambient air being cooler, and better voltage regulation means you'll be more stable at a slightly lower voltage, and provide cleaner power, which will ultimately affect the lifespan of the product.
90mm Axial Fans vs 75mm/Radial
90mm fans are significantly quieter and cool much better than their smaller 75mm, 80mm fans, which produce an extremely high pitched buzzing when at faster speeds, as typical of smaller fans. You also want to avoid radial fans, as common on reference designs, as they are louder and have less CFM (though they do have high amounts of static pressure). Cards like the XFX DD, Twin Frozr III, and Gigabyte Windforce 3 are extremely loud compared to other models due to their smaller fans, and weaker, meaning they will be louder for the same cooling.
VRM Heatsink
It's more important the card has one at all, then whether it's a large plate joined with the memory and heatsink, or a dedicated heatsink. The claims that the VRM being attached to the heatsink or on a single plate attached to the RAM being worse is silly.
VRMs have a ton of electricity running through them, meaning tons of heat, especially if there are less phases or use lower quality mosfets that run inefficiently, and therefore expel more of the energy as heat instead of power to the core and draw more power from the wall, or have no VRM cooling. All 7950 models are susceptible to coil whine, and even if a VRM stays cool, reports abound on all models of choke whine during weird things like the loading screen or when the FPS ever goes above 200. While not everyone has issue, all models have reports of coil whine, some more than others, and a VRM heatsink goes a long way in minimizing coil whine. High VRM temps also increase core temps, and vice versa, leading to a rather nasty cycle.
Be aware that if you hear coil whine, it means your VRM is getting too hot. Coil whine occurs in that dangerous range of temps, about 80-90C+, where you risk long term damage and performance degradation, so back off if you hear coil whine (this is true for any component, ie motherboards, PSUs, accessories). Even if the VRM can handle such temps, your PCB will not, as most PCBs start to brown around 90C+.
Not to mention the radiant heat will increase temps on other components, significantly. It's quite common for VRMs to get hotter than the core (same with CPU+Mobo except on higher range mobos, but GPUs only have so much real estate so even high end GPUs suffer this problem commonly).
Better Cooler
Innovation and how well a heatsink is designed, really can only account for maybe a degree or two. Just like with CPU cooling, heatsink surface area is more important, and, the size and speed of the fans used is absolutely the biggest factor. That said, certain heatsinks are better than others - ie, the Asus DC2 and Sapphire Vapor-X, as tri-slot cards, are simply much larger, and cool better, than their dual-slot cousins.
Be aware that when I say 'terrible cooler' in regards to 7950s, I mean relative to other coolers. The difference between, say, the IceQ Turbo (the worst) and Asus DC2 V2 (the best), is maybe 5-15*C at most depending on the heat range tested.
It's up to you and what you do, that determines how important this margin is - as the better the cooler, the lower you can run the fan speed for the same performance. So you might not push bleeding overclocks, but you may not want any fan noise since your PC is right next to you, and you want to minimize fan noise coming through your microphone when you stream or are in teamspeak in a team game.
If you plan to replace the cooler, then this simply doesn't matter to you, which opens a lot of options, as some 7950s are great but just have bad coolers, which would make most people overlook them, like the Gigabyte WF3.
Build Quality, Outstanding Issues
Certain cards just have those certain issues. Older Gigabytes are more susceptible to coil whine due to lack of passive VRM cooling, Twin Frozr IIIs have outstanding build quality, Sapphires use cheapo plastic and rattle, Asus DC2 V1s have mounting issues.
Unfortunately, due to 'updates', there is no such thing as a 'Perfect 7950' being sold as brand new anymore. In order to get a 'Perfect 7950', you need to either buy a used, older version, or hope a retailer gives you old stock. Fortunately it is easy to identify which model 7950 a card is, so finding a 'Perfect 7950' used shouldn't be too difficult and all these GPU companies offer serial-number warranty so you are still covered even second hand without original receipt (unofficially, of course).
Finally, be aware of the Power Limit issue. AMD insists these cards are 250w, and use that as a selling point on how they are energy efficient compared to the Nvidia offerings... but in reality these cards use more like 300w+, even on 'stock'. So what happens, is that these cards throttle themselves, even at +20% Power Limit, and you get stutter, and reduced performance. Review sites often don't do this, so report (more) negatively on the 7950 then when it's run correctly, ie 7950 stutter, etc.
Be aware that even on a stock 1ghz@1.25v clock setting, there is so much throttling that at the stock +0% Power Limit setting, compared to +50%, you'll see about a 40% drop in FPS in both games and benchmarks. This is not merely a tweak, this is mandatory. There is zero damage or risk to raising the power limit - if you raised the power limit to +10000%, the card will still use only ~300-400w as it desires.
The problem is when the power limit is below what the card demands. You can see evidence of GPU throttling by looking at your card's clock speed or utilization on a graph (hwinfo, afterburner show this) - your card's core clock on load should be a flat line at the max frequency, and it's utilization at 99-100% as a flat line. When throttling is occuring, it'll drip and drop, and be anything other than a flat line.
So any official 7950 benchmark you review you see, add a 20% overclock, and then on top of that, add 40% for the power limit, and you can quickly see why most review sites are useless and untrustworthy, and why this card is held in such high regard.
How to increase 7950 Power Limit
http://forums.overclockers.co.uk/showthread.php?t=18509458
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Aftermarket Cards
Note: X/X refers to old/new model
XFX Double D
This card is universally panned for being hot and loud. With 2x75mm fans and no VRM cooling, it is prone to coil whine. Frankly it's the worst 7950, but sometimes it's cheap enough to be the best choice.
There is a new version of this card that is actually even worse, and along with worse features, cannot have it's BIOS edited.
Core Voltage: Yes/No
Memory Voltage: No
Memory: Elpida
PCB: 7950 Reference/7950 Cheapo
Fans2x75mm
VRM Cooling: None
Cooler:Worst
MSi Twin Frozr III
This card has amazing build quality with it's steel shroud and looks great, but has a poor cooler due to 75mm fans, being second only to the XFX DD as the worst cooler. Otherwise, the card is pretty good. However, be aware that there are 2 versions of this card, and it was the old version that was so famously awesome with a 7970 PCB, Hynix RAM, and full voltage control (ie, a perfect card).
With Core and Memory voltage control, if the cooling isn't an issue (ie only gaming or running out of case, or replacing the cooler), this can be a great card, especially if aesthetics and tweakability are what's most important. As opposed to a stronger/quieter cooler of the Sapphires or better RAM of the Gigabyte.
Core Voltage: Yes
Memory Voltage: Yes
Memory: Hynix / Elpida
PCB: 7970; Cheapo 7950
Fans 2x75mm
VRM Cooling: Plate
Cooler:Weak
Gigabyte Windforce 3
New revisions are coming out with the voltage locked at the hardware level, and with 3 fans it is extremely high pitched and loud. On top of the dBa, ie loudness, is the high pitch that comes with smaller fans. The cooler is also significantly weaker than 2x92mm fan models, but still a better than the TF3/XFX DD. It has been known to rattle.
The older model did not have VRM cooling, but uses IR Digital VRMs just like Gigabyte's motherboards, meaning they are high quality and run as cool as most other VRMs with cooling. Given it's Hynix RAM, this makes the older 7950 model the best dual-slot 7950 model, especially with aftermarket cooling, ie a perfect card if you don't want a 7970 pcb.
The newer voltage locked 7950s are still great for GPGPU work as they are the only 7950s that still ship with Hynix 100% of the time, and you aren't going to be messing with voltage much anyways. I would not recommend the newer cards as much for gaming due to the weaker cooler.
Basically, I'd recommend these cards for GPGPU work or the older models if you want a 'perfect card' with either a weaker cooler or you plan to replace the cooler, and the newer models if GPU VRAM performance is most important. I would frankly not recommend these cards for gamers or overclockers who don't plan to replace the cooler.
Be aware new models ship with 8+6 power inputs although they are still 7950 PCB. Also, there was an uncommon issue with some of the older versions SMD capacitors blowing up at the most random times.
Core Voltage: Yes/No
Memory Voltage: Yes/No
Memory: Hynix
PCB: 7950 / (New models use 8+6 power inputs with 7950 PCB)
Fans 3x75mm
VRM Heatsink: None / Dedicated
Cooler: Mediocre
Sapphire Dual-X
There are the 2L, 3L, FLeX, and 950mhz versions. There are also multiple types of each, which makes things extremely confusing for this card. There are also multiple variations of the cheapo plastic heatsink used, which rattles really badly. Tapping it with a mallet helps...
The 'FLeX' is the ability to use 3 monitors without 2 of them needing to use displayport like most cards.
Be aware the 3L does NOT have VRM temp sensors or Memory Voltage. This is because it does not use the popular CHiL PWM for voltage regulation, but instead some no-name chip.
These are great cards for the price if you are focused on gaming, and prefer more silence/cooling to memory voltage control and aesthetics of the TF3, or the Hynix of the Gigabytes, and you don't mind a cheapo feel. You are the type of person who cares more about the Tahiti guts and price than the bells and whistles.
Finally, the 950mhz version is a 7970 'Perfect' card that's discontinued.
2L
Core Voltage: Yes
Memory Voltage: Yes
Memory: Hynix/Elpida 50F
PCB: 7950 Reference
Fans 2x90mm
VRM Heatsink: Dedicated with RAM Plate
Cooler: Average
3L
Core Voltage: Yes
Memory Voltage: Yes/No
Memory: Hynix/Elpida 60F
PCB: Custom 7950 8+6/Cheapo 7950
Fans 2x90mm
VRM Heatsink: Dedicated
Cooler: Average
Powercolor PCS+
This card is known for being quiet, but that's simply because the fans on it are run at a lower speed relative to other cards. It looks good and has good build quality.
Newer models ship with Elpidas instead of Hynix.
I can't quite find a niche for this card, especially given it's generally expensive price relative to the other models. Maybe if aesthetics are important but you don't want a relatively loud TF3 and don't mind the loss of tweakability.
Core Voltage: Yes
Memory Voltage: No
Memory: Hynix/Elpida
PCB: 7950
Fans 2x90mm
VRM Heatsink: No
Cooler: Average
HIS IceQ Turbo
This card is in the style of a reference card, but isn't. It ships with significantly lower voltage and clocks at stock than any other model, so the cooler scores decently on reviews when in reality it's only competitive due to being nearly 0.2v lower in voltage and underclocked.
The cooler is absolutely horrible relative to the other aftermarket models, it uses a radial fan which have half the CFM as normal, axial fans, and just a single fan instead of 2 fans. Furthermore, it's heatsink is 1/3rd the size of other aftermarket coolers. That said, it still beats the 2x75mm XFX DD and TF3. It's basically an oversized reference cooler.
That said, the internals of the card are solid if you plan on replacing the cooler anyways. It's really just a reference card in sheep's clothing.
Core Voltage: Yes
Memory Voltage: Yes
Memory: Hynix / Elpida
PCB: 7950 Reference
Fans Radial
VRM Heatsink: Plate
Cooler: Mediocre
HIS IceQx2
-image limit on at-
This card is larger than average, and has a larger heatsink, so be careful of case compatibility issues if you fill up your HDD slots or have a sideways mounted HDD rack. As such, it has the best cooling of any dual-slot model.
New cards are coming out with Elpidas instead of Hynix.
This model is truly the best dual-slot card if you consider the 7970 PCB a plus (something that is bad for scrypt GPGPU work). It's got everything you can ask for in a 7950, a real gem for a gamer or overclocker.
Core Voltage: Yes
Memory Voltage: Yes
Memory: Hynix/Elpida
PCB: 7970
Fans 2x90mm
VRM Heatsink: Plate
Cooler: Good
Sapphire Vapor-X
-image limit on at-
This is a 2.5slot card, but isn't significantly cooler than a Dual-X as it's basically a Dual-X with a tiny bit more surface area (even same 2x90mm fans). New ones come with Elpida instead of Hynix. It uses a custom 7950 PCB with an 8+8 pin pci-e power connections (older models used 8+6).
Be aware that there are significant VRM temp issues with this card, and that Sapphire has reduced the voltage below spec on the RAM to address this. Honestly, there's no reason to buy this card, it's always more expensive, and the tri-slot cooler is not significantly better than a Dual-X.
On top of all of this, the card is voltage locked. You might access some level of voltage control if you hunt for the right version of modded beta Trixx but even then, you'll still have limited control. It's a bad card.
http://www.xtremesystems.org/forums/showthread.php?284714-Sapphire-HD7950-3GB-Vapor-X-Review
Core Voltage: No
Memory Voltage: No
Memory: Hynix / Elpida
PCB: Custom 7950 (8+8 / 6+6)
Fans 2x90mm
VRM Heatsink: Dedicated
Cooler: Good
Asus DC2
-image limit on at-
There are 2 revisions, V1 and V2. V1 has a mounting issue where you need to use a shim or washers to tighten the mount. The V1 has 5 pipes, V2 has 6, but the V2's pipes are thinner so the volume, and thus cooling ability, remains the same.
The V1 also uses a reference 7950 PCB and no passive VRM cooling, while the V2 uses a custom high quality PCB with a high end VRM and passive VRM cooling. Both use high quality VRMs, so passive cooling isn't even necessary.
This is an awesome card, no downgraded versions, always comes with Hynix, but availability can be limited at times. It's a 3 slot card, and due to the 100mm fans, quieter than any other per performance. This is flat out the best 7950 model if the 3-slot size is not a compatibility issue. I would even go for the V1 if you don't mind putting some washers on it.
The build quality is also by far the best, even better than the TF3, and the PCB is coated black, rather than fabricated black (which is good). The shroud is all solid, smooth metal, and there are even green/red SMD LEDs to indicate if the PCI-E power is plugged in.
Note there are 2 versions of the V2, sold at different stock clock speeds. They are identical in every way.
Unfortunately these models are just starting to ship with Elpida 60F and voltage locked@1.09v, any model with BIOS 113-AD38900-105. These cards also cannot have the older 101 or 104 BIOS flashed.
Core Voltage: Yes/No
Memory Voltage: Yes
Memory: Hynix/Elpida 60F
PCB: 7950 Reference/7950 Custom High-End
Fans 2x100m
VRM Heatsink: None/Dedicated
Cooler: Best
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Reference Cards
Sapphire 4L
Core Voltage:
Memory Voltage:
Memory:
PCB: 7970 PCB
Fans
VRM Heatsink:
Cooler:
MSI Reference
Core Voltage: Yes
Memory Voltage: Yes
Memory: Hynix
PCB: 7950 Reference
Fans 1x75mm
VRM Heatsink: Reference
Cooler:
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Overclocking & Software
You want to overclock your 7950 using software. You can use BIOS editing, but that's very complicated for very little reward (like for any GPU). You are more than welcome to search on how to do it, just keep a copy of your original BIOS saved (use GPU-Z to save your BIOS). However sometimes there is reason to overclock via BIOS, such as if you run a Linux system. Your best bet is to search on people's who've edited the BIOS for the model you have, and check here: http://www.overclock.net/t/1395490/ati-hd-7950-7970-bios-mod-thread/0_100
First step is do the +50% Power Tune, as I mentioned above. Despite AMD insisting it's a 200w card, even on stock settings, you are going to go over 200w. That, or the card will throttle, and unless you put in a +50% Power Tune, the card will throttle, hard, and cause stutter and inconsistent FPS, especially with an overclock.
To overclock your 7950 using your preferred software program, just increase core frequency as necessary, if unstable, add voltage while making sure temps stay in line (80-90C, 1.3-1.4v max, 90-100C VRM). Remember, it's common for VRM to overheat before your core on a graphics card, so if you don't have a VRM temp sensor on your model, and you don't have a discrete temp sensor or discrete thermal diode like with your case or with a fan controller, then you should at least make sure to stop if you hear coil whine, or if you can't hold your finger on the back where the VRM is for more than 3 seconds (I'd say 80C+ is when you can't hold for more than 3 seconds) . Then, increase memory clock with your GPU core clock/voltage applied, and increase memory voltage as necessary (if you can). If memory clock is more important to you, then start with your memory overclock first (like if you run scrypt GPGPU work). Then stress test.
A good starting point is 1050mhz Core, 1.15v. A good card can do better than 1100mhz@1.2v I'd say? If you can do 1200mhz@1.2v or better, that's really a great card. For VRAM, 1500-1600 for Elpida 50F, 1600-1700 for Elpida 60F, and 1700-2000 for Hynix.
For stress testing, 5 minutes of OCCT Error Test will really make sure it's rock solid, and is really the gold standard much like 24 hours P95 custom blend is for CPU/RAM. If all you do is game, then gaming is really enough of a stress test (unless you stream, crashing or artifacting during a stream really, really sucks, in which case OCCT should probably be your standard). Stability is relative, so it's up to you how thoroughly you want to stress test (hey, you got newbs to pwn, who cares if the enemy turns purple vs I play hardcore Diablo2X with a poison necro, I will literally cry if I die again because I crashed during Act4 Venom Lords or maybe you don't want to be sending useless data to cure
What Error Test does, is run the same image over and over, without moving, and compares it to the image previous, to make sure no artifacts occurred. Most artifacts are too tiny and quick for the eye to see, and besides, do you really want to spend your time overclocking staring at a red donut for 5 minutes on end? For reference, I find that Error Test will knock me down about 60-100mhz from what appeared to be artifact-free in Furmark/Non Error Test OCCT, and I've had Furmark stable have crashes in GPGPU work but never OCCT Error Test stable. Conversely, if I could pass 5 minutes of Furmark/Non-Error Test, I never have had a visible artifact or driver crash in-game. You need to judge for yourself what's more important, a .0001% chance of crashing, or 20-50mhz extra core clock.
There's a few different suites, use what you want, but basically:
MSi Afterburner: This is basically the popular 'Rivatuner', which is the best GPU overclock program, which by extension makes AB the best overclock program. It's got a great UI, custom skins, custom fan profile, and access to lots of options and profiles. You may need to use 'Unofficial Afterburner' to have access to voltage control, or mess with the user control mode (kernel vs user, just check in options):
To enable the unofficial overclocking in this version it is necessary to edit the MSIAfterburner.cfg file located in the installation directory of AfterBurner (typically Program Files (x86) MSI Afterburner):
You need to alter the following:
Seek UnofficialOverclockingEULA field and add following text:
I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
Set UnofficialOverclockingMode to 1 to keep PowerPlay active (may not work on old ASICs), 2 to traditionally disable PowerPlay or to 0 to temporary disable unofficial overclocking path
http://event.msi.com/vga/afterburner/download.htm
Sometimes you just can't get to voltage control, or memory voltage control in AB, in which case try another GPU overclock program, like....
Sapphire Trixx: Got all the bells and whistles of AB, there are multiple versions of Trixx, available on the official website, but just not as polished as AB. They are always changing the max core voltage limit, so use different versions of Trixx if you want more than that allowed in the version you downloaded (although you have to have some pretty strong custom loop to be saying 'oh man 1.3v is not enough!'). There is also unofficial Trixx 4.3 and 4.3, or modded Trixx, in case you still can't get memory voltage control....
Official Trixx: https://www.sapphireselectclub.com/ssc/TriXX/
Trixx 4.3 Mod: http://www.mediafire.com/?08jizxzm2z2ajaa
Trixx 4.4 Mod: http://www43.zippyshare.com/v/83298134/file.html
AMD Overdrive: I don't think many people really use this, should come in the Catalyst Control Center if you downloaded that. Works just fine, it's all the same really.
Aftermarket Cooling
Replacing Thermal Paste
GPUs always use high end thermal paste, so unless you got an old card (which will inevitably have old, outdated paste), replacing the paste will not yield much at all. Replacing the paste of a 4850 or GTX280 with a modern, high end paste is a great idea. Replacing the paste of a 7950 or GTX780, is not. Anything less than Phobya HeGrease will literally result in an increase in temps, and even Coollaboratory Liquid Ultra will yield you maybe 1-3*C (which may or may not be worth it for you).
For reference, using CLU on my Sapphire Dual-X 7950 yielded a 1C temp drop (and I remounted twice, yes I know what I'm doing, and both times). In 5 years, when new advancements occur in thermal paste, I'm sure then, you can replace the thermal paste for a drop in temps on a 7950.
Using 2x120mm Fans
The stock fans on these heatsinks are running at almost 4K RPM, so some 2x1200RPM Noctua fans is going to significantly increase your temps by 20C+. Also, a lot of your CFM is going to be lost from overhanging the heatsink. A 120mm to 92mm adaptor would be nice theoretically, if it existed or you modded one, but basically, if you think you can just run some 120mm fans on a medium speed and be infinitely quieter and cool the same as 2x92mm fans on 100%, you are dead wrong.
You'll need to run your 120mm fans at a good 3k RPM+, and you also need to make sure they have tons of static pressure. I wouldn't even expect 2x Gentle Typhoon AP15s to decrease temps for you, you really need 120mm fans running the same 4K RPM to have better temps. Sorry to burst your bubble, I learned this the hard way. I tried 2x Sickleflows (true, bad static pressure and only 1800RPM, but they're still 120mm fans) and I had over 20C+ temp increase over the stock Sapphire Dual-X 2x92mm fan cooler.
Aftermarket Air Coolers
Arctic Acceleros with 3x92mm fans will drop temps about 15-25C. Decent, if pricey. There's also the Prolimatech MK-26, which will drop temps about 20-30C with 2x120mm fans. These can be quite effective, but generally are overpriced and they are also quite large, so make sure they fit! They really don't seem that big in pictures, but they are.
Actic Hybrid
The hybrid cooler is just basically 'The Mod', a 120mm closed loop stuck to the heatsink. Overpriced when it's more than $60, 70.
'The Mod', Dwood Bracket, Sigma Cooler, Drilled out Asetek Mount
This should result in a strong 25-40C temp drop, and that's just with a medium fan on an old H50 or 620. You really have no need to get a big LQ320 or H80 here, just get the cheapest closed loop you can find, or best value budget loop. An H50 can be found on Ebay or on sale for $20-30 shipped, and H60s, 620s, and many other decent closed loops go for $30-45 all the time. It doesn't really matter which you pick.
There are essentially only 2 different closed loops - Asetek and Cool-it ECO's (with about 3 generations for each). You can only mount Cool-it's, square block like H60s, with a Dwood Bracket or a sheet of metal that you cut with a band saw or dremel or router. You can mount Aseteks, ie round block like 620, Zalman, H50/H55, etc, with the Dwood asetek block, Sigma Cooler, or just simply take the Intel bracket and drill holes where the GPU holes line up and use some bolts!
You can also use cable ties to hold down your heatsink. Make a 'ring' around the block, then slip 4 ties through the ring (you can actually use a legit ring, like those used to hold pipes and such, from the hardware store, if you care), then ehume- Ziptie screw them:
http://www.overclock.net/t/753254/ziptie-screw/0_100
Make sure to use VRM heatsinks. VRAM heatsinks aren't as important, but it is definitely important to put a VRM Heatsink on your RAM-VRM if you intend to mess with Memory Voltage. I have never heard of VRAM blowing, but there are reports of VRAM-VRM blow-outs. Some aluminum pieces will work just fine, you can buy large packs like a 40 piece pack or an Arctic Cooler GPU heatsink piece set, for $5-8 shipped. Copper Enzotechs are way too expensive at $15+ and are ugly. You can strap a fan using cable ties to cool the VRM (92mm fits the best, but whatever you want).
You also need to use a copper shim, as the aluminum cap around the the 7950 chip actually prevents you from making perfect contact (see that weird 'thing' that makes a diamond around the actual chip?). This was implemented by AMD because so many people were crushing their GPU dies, or chips, with their water blocks. So, now you need to put die/paste/shim/paste/cooler to make the best contact. It isn't needed, you can still get a drastic reduction in temps without it, but there's no reason not to get one considering it's efficacy and that it only costs 50 cents shipped on ebay. It needs to be at least 20x20x0.5mm in dimension (thicker shims are fine, bigger shims are okay and even 25x25 is fine if you cut the edges a bit).
Custom Loop
There's plenty of stuff out there on water blocks, that's a guide on it's own. They generally cost upwards of $100+ for just the 7950 water block, or $60+ for universal CPU/GPU blocks. Make sure that if your card has a 7970 PCB, you get a 7970 water block. Many an enthusiast has been messed up by this. Of course, this beats the previously mentioned solutions by far.
Which card to buy?
It all depends on your needs. If all you are doing is gaming which won't really stress a card much anyways, than all of the coolers will be sufficient, but if you do intensive GPGPU work then all of the coolers will be inadequate for overvolting. Conversely, if you want a quieter card while gaming, you might want to go for the better cooler.
If you do GPGPU work, how good the cooler is might mean something if you run incase, but if you run open case or on a test bench or milk crate, you might not care how loud the fans are or how strong the cooling is. Or, whatever your use is, you might just use an H60 mod or a water block anyways.
Memory clocks are far more important than core clocks for GPGPU work, with ~100mhz yielding up to an extra 50-100hash (depending on core clocks due to the sweet spot core:memory dynamic). Hynix also will yield better results clock for clock.
So what card you buy, all depends on your uses and the price. The XFX DD has been known to be super cheap at times. A TF3 would be great for a gamer build with a side panel window, a Dual-X would be great for a gamer who plays with the computer right next to them, a HIS IceQx2 would be great for a gamer who really loves to overclock. A gigabyte or TF3 would be fine for GPGPU work out of case, while a Sapphire might be better for GPGPU work inside a case. Or maybe you just use a TF3 and replace the fans for inside a case.
Due to all the 7950s being revised, my recommendation is to get an older Gigabyte or Asus model off Ebay, OCN market, etc, and identify what revision is used (either the pics provided or ask the seller). I'd go with the Asus, definitely, if you plan to keep the stock cooler, and then the Gigabyte or Asus if you planned to change the cooling depending on if the 3-slot size bothered you and preferences on the PCB color and VRM quality.
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