Mini ITX DIY vs. Pre-built SFF: Is it worth it for an everyday computer?

[cbn]

Recent price drops of some SFF parts got me thinking about how a budget DIY mITX PC compares to a mass produced budget SFF PC from a value standpoint.

While thinking about this, here are some factors/considerations in favor of the DIY PC that crossed my mind:

1. Overclocking and underclocking/undervolting: Possible with DIY depending on the components and manufacturer.
2. DIY uses standardized components (including motherboard) and thus can be re-built. Pre-Build SFF PC may or may not use standardized parts.
3. Windows 8 System builder is a re-usable component (through the personal use license) when purchased for DIY and thus can be transferred to subsequent builds. A mass produced Pre-built PC contains a version of Windows 8 that is tied to the motherboard (so even if the pre-built chassis and other components can be re-used, a new OS will need to be purchased if there is a mainboard swap.)
4. Price: Pre-built SFF PCs can often be found on sale, but deals exist for DIY as well (eg, Microcenter CPU deals, Fry’s CPU/motherboard bundle, Free 8 GB ram deals from Newegg with Biostar mainboard purchase, etc)
5. Warranty can be longer on individual DIY parts vs. brand new pre-built PC (Eg, a HP slimline carries a 1 year warranty, but many DIY parts (even cheap ones) carry warranties longer than that.)
6. A DIY SFF PC build does not come with bloatware.
7. A much greater amount of testing can be found online with regard to thermal and noise performance for DIY SFF cases vs. mass produced pre-built SFF (with the exception of certain Boutique Pre-builts). This could be important if the system needs to be upgraded.
8. A group of features may be needed for a SFF PC that cannot be found in a pre-built.

One obvious draw for DIY is overclocking, but even at the lowest price points (where the parts can’t be overclocked on the Intel side) I think an argument can still be made for DIY mITX PC over the Pre-built SFF PC.

Example:

http://www.newegg.com/Product/Produc...82E16883155554
(Dell Inspiron i660-769BK Desktop, $289.99 for free shipping, 1 year limited warranty parts and labor.)

The above SFF PC is the cheapest I could find on Newegg. Here are some of the specs:

1. Celeron G465(1.9GHz)
2. 2GB DDR3
3. 500GB HDD
4. 16x DVD burner
5. Windows 8
6. Keyboard and mouse
7. 802.11 b/g/n wifi card
8. Usb 3.0

Here is a DIY SFF computer I pieced together (to best approximate the Dell SFF PC):

Motherboard:

http://www.amazon.com/dp/B0091158A6/?tag=pcpapi-20
(ECS H61 Mini ITX, $44.99 with free shipping, limited warranty 3 years for parts and 2 years for labor. NOTE: this board does not have a PCI-E x16 slot)

Or

http://www.amazon.com/dp/B0065SM75M/?tag=pcpapi-20
(Foxconn H61S Mini ITX, $49.99 with free shipping, limited warranty 3 years for parts and 3 years for labor.)

Or

http://www.macmall.com/p/6431245?dpn...ource=zwb12166
(Intel DH61DL Mini ITX board, $69.99 with free shipping, limited warranty 3 years for parts and 3 years for labor. NOTE: this board does not have a PCI-E x 16 slot, but does have USB 3.0)


CPU:

http://www.amazon.com/dp/B00B4BJYVU/?tag=pcpapi-20
(I couldn’t find the Celeron G465 for sale at any of the major retailers, but this Celeron G1610 is faster and only $42.99 with Free shipping. 3 year warranty)

RAM:

http://www.amazon.com/dp/B006TTQGF4/?tag=pcpapi-20
(Wintec value ram 1 x 2GB, $16.06 with free shipping, limited lifetime warranty)

Hard drive:

http://www.amazon.com/dp/B000EY5F5C/?tag=pcpapi-20

(Seagate Barracuda 500 GB SATA HDD, $54.99 with Free shipping, 5 year warranty)

Optical drive:

http://www.newegg.com/Product/Produc...D=3938566&SID=
(Samsung Internal slim SATA DVD burner, $18.99 with free shipping, 1 year limited warranty)

Operating System:

http://www.amazon.com/Windows-System.../dp/B0094NY3R0
(Windows 8 system builder , 94.81 plus free shipping)

Case:

http://www.amazon.com/gp/product/B00...2?tag=at055-20
(Silverstone Sugo SG05 lite, $39.99 with free shipping, limited 1 year warranty)

PSU:

http://www.newegg.com/Product/Produc...089&nm_mc=AFC-

(Seasonic 300 watt SFX PSU, $39.94 after 15% promo code, $4.99 shipping, 3 year parts and labor warranty)


Total price (this includes shipping):
$357.76 for ECS miTX mainboard version
$362.76 for Foxconn mITX mainboard version
$382.76 for Intel mITX Mainboard version


When compared to the Dell SFF pre-built we have a price difference of $67.77 for the ECS mITX build. Substituting Foxconn and Intel mainboards (for the ECS) in the DIY build increases this difference by $5 and $25 respectively.

I don’t think $67.77 more for the DIY build is bad at all (even at this value level) when we consider the extra advantages the DIY build has in certain scenarios.

NOTE: When comparing price of the DIY mITX builds to the Dell SFF realize the DIY builds do not come with wireless card, keyboard and mouse (and in the case of the ECS and Foxconn mainboards USB 3.0 is missing).

P.S. If anyone is wondering about case volume differences between the SG05 build and the Dell SFF PC here is what I came up with:

Internal volume of Dell SFF PC = 608 cubic inches
Internal volume of SG05 = 657 cubic inches

The SG05 has about 8% more case volume compared to the Dell SFF PC. Certainly the Dell SFF PC has a smaller footprint on the desktop compared to the Sugo. Still I thought the differences were minimal enough to include the SG05 in this comparison.

 

[Sleepingforest]

DIY PCs are very weak in terms of value/$ in the low end--you can't really beat a Dell Outlet refurb in power for the price, especially with a Windows license factored in.

That being said, if you want anything more than an office machine, you'll need to go custom to get real value (I'm talking gaming PCs here).

 

[cbn]

you can't really beat a Dell Outlet refurb in power for the price, especially with a Windows license factored in.

http://outlet.us.dell.com/ARBOnline...arch.aspx?c=us&l=en&s=dfh&cs=22&puid=350523e9

I did find the same Dell Inspiron 660 (linked above) at the outlet in refurbished condition. It is $10 less than the new model at Newegg, but they do add in a 4GB stick of RAM bringing the total to 6GB. (I did find out Dell Outlet has some 20% off coupons, but these only apply to new desktop models.)

 

[Insert_Nickname]

If you just need a basic system, that Dell is enough. I know, I use a G465 myself. Its perfectly adequate for basic use. The upgrade potential is seriously limited of course and you might have to add the cost of additional RAM though, 2GB is kind of on the very low side.

 

[DaveSimmons]

Gateway and Acer make mini-ITX SFFs that are reasonably cheap and run quietly (at least the intel CPU models do). I've had an Acer for the music jukebox in my home office for a couple of years now, and we got my mom an almost identical Gateway for her birthday a year ago.

It was nice not having to build and test either system. I know people like to build for buiding's sake, but I build my gaming desktops mostly because for that level of system ($1,500+) I'm more picky about parts. For a work- or mom-puter I care less about the parts brands or expandability.

 

[cbn]

Since the Celeron G465 in the Dell Inspiron 660s is only a 1.9 ghz single core (with HT) I figured I could probably swap in a lower spec processor for DIY build. This, of course, to lower costs.

Instead of the much stronger 2.6 Ghz Celeron dual core found in my original DIY build, I swapped in a Celeron 847 1.1 Ghz dual core.

Is a 1.1 Ghz dual core a rough equivalent to the 1.9 ghz single core with HT found in the Dell? For some situations the answer should be yes, for other situations the G465 should be better. Certainly the G465 is going to have much better single thread performance. It also has a better iGPU (see below).

From Intel Ark:

http://ark.intel.com/products/69363 (Celeron G465 iGPU = base clock 650 Ghz, max clock 1 Ghz)

http://ark.intel.com/products/56056/Intel-Celeron-Processor-847-2M-Cache-1_10-GHz (Celeron 847 iGPU = 350 Mhz base clock, max clock 800 Mhz)

Some other notes: I also downgraded the case to a Rosewill mini ITX (with supplied SFX PSU). The slim optical drive was also swapped to a desktop sized optical drive...a change that also saved a few bucks.

New build:

CPU/mainboad:

http://www.newegg.com/Product/Produc...82E16813128585

(GIGABYTE GA-C847N-D Intel Celeron 847 1.1GHz Intel NM70 Mini ITX Motherboard/CPU/VGA Combo, $49.99 after $20 rebate, free shipping, 3 years parts and labor warranty)

RAM:

http://www.amazon.com/dp/B006TTQGF4/?tag=pcpapi-20
(Wintec value ram 1 x 2GB, $16.06 with free shipping, limited lifetime warranty)

Hard drive:

http://www.amazon.com/dp/B000EY5F5C/?tag=pcpapi-20

(Seagate Barracuda 500 GB SATA HDD, $54.99 with Free shipping, 5 year warranty)

Optical drive:

http://www.newegg.com/Product/Produc...82E16827106289

(LITE-ON DVD Burner, $14.99 with free shipping, 1 year limited warranty (parts and labor))

Operating System:

http://www.amazon.com/Windows-System.../dp/B0094NY3R0
(Windows 8 system builder , 94.81 plus free shipping)

Case/PSU:

http://www.newegg.com/Product/Produc...82E16811147131

(Rosewill RS-MI-01 BK Mini ITX Tower/ Desktop Computer Case with 250W, $43.99 after 20% promo code and $3.99 shipping, 1 year parts and labor warranty)

Total price after rebates (this includes shipping):

$278.81

The cheapest price I could find a new G465 2GB Dell Inspiron 660s (using a recent, but expired coupon) was $224.99 with free shipping.

That still puts the DIY model $53.83 more than the cheapest past coupon price for the new Dell.

Of course, the Pros and Cons still need to be factored in. I still think the transferable System Builder license is a big plus for going DIY. The lack of bloatware helps also (re: If a person does not have a tech savvy person in the family most places will charge money to remove the bloat....adding further to the price of the PC.) Still, I admit the Pre-built Dell (with coupon) seems like a really good value. Remember that the Dell (in addition to having a more powerful processor) comes with USB 3.0. I am hoping budget DIY mini ITX mainboards rectify the lack of USB 3.0 in the future. Also realize the Dell includes Keyboard and mouse (items which I did not include in the final price tag for the DIY build).

 

[jihe]

Other advantage for prebuilt is size. You can find some really compact machines. I think for SFF this is pretty important.

 

[cbn]

A closer look (from a ventilation standpoint) at the Dell Inspiron 660s chassis:

There appears to be no case fans. (only exhaust fan is the psu fan). There are some ventilation holes next to the motherboard I/O panel though.

Two expansion slots are included, positioned at the top of the chassis.

Notice the ventilation holes at the top of the enclosure. I believe this is primarily for exhaust, but I assume it could also provide some cool intake airflow for a low profile video card. (NOTE: A dual slot low profile card cannot be used because the PCI-E express x16 slot is positioned outboard to both the mini card slot and pci-e x 1 slot on the Insprion 660s motherboard.)

Here we take a look inside the case. Dell has included a black plastic fan shroud to help duct cool air to the CPU heatsink. Apparently this set-up (without video card) is good for up to 65 watts as dell lists a Core i5-3330s as the top processor for this chassis.

With that said, I wonder how well a CPU and low profile video card would play together? There are no case fans in the chassis and low profile video video would not only increase the thermal load, but also block heat from the CPU escaping out the top.

Perhaps in the situation of a using a low profile video card orienting the Dell Inspiron 660s in the horizontal position would help? This would increase the footprint, but I am thinking the rear ventilation holes near the motherboard I/O panel might be more effective in this arrangement.

 

[cbn]

ftp://ftp.dell.com/Manuals/all-prod...esktop/inspiron-660s_Owner's Manual_en-us.pdf

Above is the owner's manual for the Dell Inspiron 660s.

On page 15 is a diagram of the 660s motherboard. It lists the following components:

1 power button connector
2 battery socket
3 Two SATA connectors (one of which is 6 Gbps)
4 password reset jumper
5 PCI-Express x16 card slot
6 Mini-Card slot
7 PCI-Express x1 card slot
8 front-panel audio connector
9 Two DIMM slots
10 processor socket
11 24 pin power connector
12 4 pin aux power connector
13 processor fan connector
14 Two front panel USB connector
15 CMOS reset jumper

Here is a close-up picture of the actual motherboard:



To my eye it appears to have a mix of solid and electrolytic caps. (Although the DIY Gigabyte board with BGA Celeron 847 has all solid caps, all three boards in my first DIY build up were a mix of solid and electrolytic caps.)

Noteworthy is the relative lack of SATA ports. It only has two---one for the full size optical drive and the other (6 Gbps) for the HDD.

Still I like the fact this Dell motherboard (via the B75 Express chipset) has both USB 3.0 and SATA 6 Gbps (even if it is just one port) at such a low price point.

 

[cbn]

Some pictures of the Dell Inspiron 660s power supply:



In the above picture we can clearly see the connectors. (24 pin power, 4 pin aux power, and two SATA power connectors.) Nothing extra left over, just the necessary connectors to power the stock computer.

Form factor appears to be "Flex ATX", but I am not sure if the measurements conform exactly to the specification.

NOTE: For someone contemplating an upgrade to a low profile discrete video card, I think it is important to mention the lack of molex on the PSU and lack of extra fan headers on the Inspiron 660s mainboard. If the CPU and discrete GPU combination adds too much thermal load there will be no way of providing additional cooling (ie, case fan via molex or fan header). Not sure where the cooling threshold would be however? The worst case scenario I can think of would be a 65 watt Ivy Bridge quad core and a 61 watt low profile HD7750 (made by Club 3D, the Sapphire version is rated at 55 watts). Still it is hard to fault Dell for not including extras. They are only obligated to provide what is necessary to reliably run the computer in the stock configuration.




Here is the label. The manufacturer is Shenzhen Huntkey Electric company (a manufacturer I have never heard of before.) Max output: 220 watts. The single 12V rail is listed as 18 amps.

Some shots of the PSU installed in the case.

.....and finally the power supply's exhaust fan.

 

[RoarTiger]

Thanks for the look inside the Dell 660. Lots of good information there.

 

[Zap]

Here is the label. The manufacturer is Shenzhen Huntkey Electric company (a manufacturer I have never heard of before.) Max output: 220 watts. The single 12V rail is listed as 18 amps.

Huntkey does not have a retail presence in the USA so you won't see that brand here. Some companies have sold Huntkey PSUs here under their own brand. They are usually considered to be decent build quality (soldering, etc.), but not high end compared to popular enthusiast PSUs in the electrical department (ripple, etc.). This makes them perfectly suited for your Dell.

18A = 216W, which is nearly the entire capacity. I wonder if it is independently regulated?

 

[cbn]

Here is the Rosewill RS-MI-01 BK from the 2nd DIY build: (The Sugo SG05 Mini ITX case from the first DIY build is well known so I not go into much detail about that enclosure.)

As can be seen from the above photos, the case has vents on both sides, but is solid on top.

A rear shot of the case showing some ventilation holes on the side opposite of the expansion slot.

A top down shot of the interior:

A side shot of the interior:




According to Assassin's HTPC blog this Rosewill enclosure is "basically identical" to the APEX MI-008 --> (scroll down to "case options" after clicking the link) http://assassinhtpcblog.com/?page_id=160#miniitx

Other references I have seen confirm this observation and indicate the only difference between the the Apex MI-008 and the Rosewill RS MI-01 BK is the front fascia. Internally they appear to be exactly the same (including the packaged AL-8250SFX power supply).

Looking at the Apex website, there is a model appearing identical to the Rosewill RS MI-01 BK listed as the MI-105--> http://www.apextechusa.com/products.asp?pID=193. So I am going to make the assumption the Rosewill case is a re-brand of the APEX design and the reviews for the APEX MI-008 can be applied to the Rosewill MI-01 (and Apex MI-105).

So moving on to reviews here are two I could find (both on the APEX MI-008):

(Before reading these links I think it is important to point out that the SPCR review was conducted in 2009. Apparently at this time the APEX MI-008 only had ventilation holes on one side of the case. By the time the second review was written in 2011, APEX had added ventilation holes to other side as well.)

http://www.silentpcreview.com/article905-page1.html

http://8000.hillbillyhardware.com:8000/Reviews/apex_mi-008/apex_mi-008.html

 

[sm625]

You shouldnt even be looking at those types of cpus in a build that expensive. It makes no sense. You could buy a used core 2 E8600 machine for $100 and it would be faster. Just spend the $40 extra to bring the performance up to G2020/A8 levels.

 

[aigomorla]

An itx system is still considered quite large compared to a NUC or a Zbox...

The Zbox will probably run u a bit more... but here is the size of a NUC and Zbox.
Here is the NUC:

Here is the NUC on top of the Zbox.

Here is why i like the Zbox more then the NUC.

I can replace that CPU to ANY 65W cpu of my choice...

and dude i am in love with ultra mini's....
I foresee myself having a stack of them piled up high after i get bored of playing with all these mini's.

 

[piasabird]

Look for father's day sale.

Inspiron 660s $279

You would be hard pressed to build something cheaper. In reality you need more RAM and a better Processor.

http://configure.us.dell.com/dellst...&model_id=inspiron-660s&c=us&l=en&s=dhs&cs=19

Software & Services
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Inspiron 660s
Inspiron660sChassiss,SFF,Blackw/8:1mediacardreader
Intel® Celeron® G465 processor (1.5M Cache, 1.9 GHz)
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Shipping Material for Inspiron 660s
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Additional Software
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Recalculating Price

 

[cbn]

Here is the Rosewill power supply label for the RS-MI-01 BK (from the second DIY build):

Some specs from the APEX website for AL-8250SFX:

http://www.apextechusa.com/products.asp?pID=42

-24Pin MB connector
-4Pin +12V connector x 1
-Peripheral power connector x 2
-SATA connector x 2
-Floppy power connector x 1

Efficiency= 65% at full load

SPCR compared this power supply to the Seasonic SS-300SFD (the SFX PSU I listed in the first mini itx build) on this page of the review.

Bear in mind they were using Atom 330 (so watts were very low at both idle and load), but here is what they said:

Compared to the 80Plus Seasonic SS-300SFD, the stock power unit consumes about 5W more at most loads. Compared to the HFX Micro and its picoPSU, the gap widens to 8-10W. Nothing surprising here: Stock power supplies are rarely that efficient, especially at the low end of the spectrum. (For more test data regarding the Intel D945GCLF2, please refer to our mCubed HFX Micro review.)

So is it worth it to change the power supply? Well if you have a more efficient one handy you might as well, but if you don't, then you have to consider whether it's worth your time and/or money. From a purely financial point of view, consider this: if this particular system was run with the stock power supply instead of a picoPSU and power brick 24-7, it would put a $5.16 CDN dent into SPCR lab's electric bill after one year — it would take many years before we would re-coup the cost of a picoPSU. Electricity rates vary from region to region, so check your rate and do some quick math. Of course, if you're seeking to be as green as possible with your IT gear, then the savings in electricity is probably more important than the money saved. However, the embedded energy in the stock PSU or recycling it complicates the environmental picture.

The Allied power supply was surprisingly quiet, more so than the Seasonic SS-300SFD, our sample of which has a rickety fan. We anticipated in advance that the stock unit would be too loud and planned on using the Seasonic instead. As it turns out, not only is the Allied power supply quieter, the Seasonic has a protruding fan that interferes with the metal guide that sits between the power supply and the I/O panel. That made the decision to leave the power supply be an easy one.

P.S. There is a discrepancy on the Newegg Rosewill RS-MI-01 listing for the power supply's connectors. In the product title (for RS-MI-01 BK) it says 1 SATA connector. However, upon reading the newegg RS-MI-01 BK reviews it does, indeed, have two sata connectors.

 

[Zap]

FYI for anyone that wants a similar case/PSU, Newegg has one of the Apex versions for $40 shipped right now.

 

[Throckmorton]

Some pictures of the Dell Inspiron 660s power supply:



In the above picture we can clearly see the connectors. (24 pin power, 4 pin aux power, and two SATA power connectors.) Nothing extra left over, just the necessary connectors to power the stock computer.

Form factor appears to be "Flex ATX", but I am not sure if the measurements conform exactly to the specification.

NOTE: For someone contemplating an upgrade to a low profile discrete video card, I think it is important to mention the lack of molex on the PSU and lack of extra fan headers on the Inspiron 660s mainboard. If the CPU and discrete GPU combination adds too much thermal load there will be no way of providing additional cooling (ie, case fan via molex or fan header). Not sure where the cooling threshold would be however? The worst case scenario I can think of would be a 65 watt Ivy Bridge quad core and a 61 watt low profile HD7750 (made by Club 3D, the Sapphire version is rated at 55 watts). Still it is hard to fault Dell for not including extras. They are only obligated to provide what is necessary to reliably run the computer in the stock configuration.




Here is the label. The manufacturer is Shenzhen Huntkey Electric company (a manufacturer I have never heard of before.) Max output: 220 watts. The single 12V rail is listed as 18 amps.



Some shots of the PSU installed in the case.



.....and finally the power supply's exhaust fan.

I have a 660ST and I thought it was a TFX PSU but I haven't looked at the specs for FlexATX to compare.

Something I'm trying to figure out... I was planning to get a Seasonic TFX 350W PSU so I can run a low profile Zotac GTX 650. The difference with the Seasonic is that it has an extra 12V 18W rail. But how can that second rail be used to power the video card?

As I understand, a) only a single rail powers the motherboard, so the same 12V rail would have to be shared with the GPU and b) 12V is the rail that matters for powering a graphics card and 5V is pretty irrelevant.

The best I could do is use the extra rail for the HDD and optical drive, which wouldn't be much help.

Should I just try running the GTX 650 with the original 220W? How many watts do an i5 3330S, 8gb RAM, HDD (may replace with SSD), and GTX 650 require?

Or do I need to get a bigger case and run a full size GPU with power input so I can take advantage of a second 12V rail?

Edit: The numbers literally don't add up. 12V*18A = 216W 5V*15A = 75W 3.3V*10A = 33W
Since they say max wattage on 5 and 3.3 is 100W that comes out to 316W

 

[Zap]

I have a 660ST and I thought it was a TFX PSU but I haven't looked at the specs for FlexATX to compare.

Look up the sizes and see which one is a match. This link may help.

Something I'm trying to figure out... I was planning to get a Seasonic TFX 350W PSU so I can run a low profile Zotac GTX 650. The difference with the Seasonic is that it has an extra 12V 18W rail. But how can that second rail be used to power the video card?

The splitting of the +12V rail
"The bottom line is, for 99% of the folks out there single vs. multiple +12V rails is a NON ISSUE."

Should I just try running the GTX 650 with the original 220W? How many watts do an i5 3330S, 8gb RAM, HDD (may replace with SSD), and GTX 650 require?

Core i5-3330S = 65W TDP*

GeForce GTX 650 = 64W

I think it would work just fine.

* Note that TDP does not strictly equal power draw. It is Intel's thermal dissipation number, and is for a "family" of products and not necessarily for a specific product.

Edit: The numbers literally don't add up. 12V*18A = 216W 5V*15A = 75W 3.3V*10A = 33W
Since they say max wattage on 5 and 3.3 is 100W that comes out to 316W

You can't "add up" rails to get a PSU's true combined and continuous wattage. The 220W is probably the entire amount that it can put out with all rails combined. 3.3+5 can't go over 100W combined, and each rail has its own limit. This is fairly normal for rating a PSU. Let's look at an example of a somewhat popular PSU.

Corsair HX650 PSU with 650W total output

Individual rails:
+3.3V@20A = 66W
+5V@20A = 100W
+12V@54A = 648W
-12V@0.3A = 3.6W
+5VSB@2.5A = 12.5W
~= 830W !!!

Why the big discrepancy? In this particular case (I'm fairly certain) the PSU is just a massive +12v unit. The minor rails (3.3v/5v) have circuitry which converts some of the +12v into the other voltages. Thus, you can't ever pull more than the roughly 650W at one time.

That is just one example. There are other ways to make PSUs tick.

+5VSB is a bit different because it is its own little PSU inside the PSU, running separate from everything else.

 

[Throckmorton]

Look up the sizes and see which one is a match. This link may help.



The splitting of the +12V rail
"The bottom line is, for 99% of the folks out there single vs. multiple +12V rails is a NON ISSUE."



Core i5-3330S = 65W TDP*

GeForce GTX 650 = 64W

I think it would work just fine.

* Note that TDP does not strictly equal power draw. It is Intel's thermal dissipation number, and is for a "family" of products and not necessarily for a specific product.



You can't "add up" rails to get a PSU's true combined and continuous wattage. The 220W is probably the entire amount that it can put out with all rails combined. 3.3+5 can't go over 100W combined, and each rail has its own limit. This is fairly normal for rating a PSU. Let's look at an example of a somewhat popular PSU.

Corsair HX650 PSU with 650W total output

Individual rails:
+3.3V@20A = 66W
+5V@20A = 100W
+12V@54A = 648W
-12V@0.3A = 3.6W
+5VSB@2.5A = 12.5W
~= 830W !!!

Why the big discrepancy? In this particular case (I'm fairly certain) the PSU is just a massive +12v unit. The minor rails (3.3v/5v) have circuitry which converts some of the +12v into the other voltages. Thus, you can't ever pull more than the roughly 650W at one time.

That is just one example. There are other ways to make PSUs tick.

+5VSB is a bit different because it is its own little PSU inside the PSU, running separate from everything else.

Ah interesting. But you missed one thing I was asking... The mobo only gets one of those 12V rails right? So the other 18amps are wasted, and it's JUST like if I stuck with the OEM 220W PSU which is also 18amps on its single rail. It may be true that "for 99% of folks it's a non issue" but it's an issue in this case.


Do you see what I'm asking? The 660ST has one 12v rail with 18a. If I upgrade that to a Seasonic with two 12v rails with 18a each, one rail just gets wasted because it has nothing to power except maybe the hard drive.

But going by the specs it seems like 220W should work for a 65W graphics card, but the manufacturer recommends a 350W PSU! Why?!

 

[Zap]

Do you see what I'm asking? The 660ST has one 12v rail with 18a. If I upgrade that to a Seasonic with two 12v rails with 18a each, one rail just gets wasted because it has nothing to power except maybe the hard drive.

Nope, you are still part of the 99%.

Reviews - Seasonic SS-300TFX 300W
"Upon opening the unit for verification, I found that it only has the one 24A 12V rail."

If you read the link I gave above about "The splitting of the +12V rail" you will see this gem.

Is it true that some PSU's that claim to be multiple +12V rails don't have the +12V rail split at all?

Yes, this is true. But it's the exception and not the norm. It's typically seen in Seasonic built units

But going by the specs it seems like 220W should work for a 65W graphics card, but the manufacturer recommends a 350W PSU! Why?!

Because they cannot control what actual PSU you have. You might have a "300W" PSU that came with a $30 case which might actually put out only 150W at low temperatures. That's pretty common with "crappy" PSUs, putting out roughly only half of the label's rating, plus only at low temperatures (as temperatures rise inside an actual computer, output goes down).

If someone who is not knowledgeable about these things have a stability problem with their rig after upgrading graphics cards, first thing that's gonna happen is they blame the card and try to RMA it (and often they will return and buy another brand, mentally labeling the "failed" one as a "junk" brand). The higher wattage requirement is an "out" for the card manufacturer. They can ask what wattage your PSU is, and then tell you it isn't sufficient. If they said what it actually requires and the user has a crappy PSU, the user will go "but my PSU is already XYZ watts!" So, a 350W requirement which means someone who ends up with a crappy PSU like this one has a chance at running a GTX 650. Barely.

 

[Throckmorton]

Nope, you are still part of the 99%.

Reviews - Seasonic SS-300TFX 300W
"Upon opening the unit for verification, I found that it only has the one 24A 12V rail."

If you read the link I gave above about "The splitting of the +12V rail" you will see this gem.




Because they cannot control what actual PSU you have. You might have a "300W" PSU that came with a $30 case which might actually put out only 150W at low temperatures. That's pretty common with "crappy" PSUs, putting out roughly only half of the label's rating, plus only at low temperatures (as temperatures rise inside an actual computer, output goes down).

If someone who is not knowledgeable about these things have a stability problem with their rig after upgrading graphics cards, first thing that's gonna happen is they blame the card and try to RMA it (and often they will return and buy another brand, mentally labeling the "failed" one as a "junk" brand). The higher wattage requirement is an "out" for the card manufacturer. They can ask what wattage your PSU is, and then tell you it isn't sufficient. If they said what it actually requires and the user has a crappy PSU, the user will go "but my PSU is already XYZ watts!" So, a 350W requirement which means someone who ends up with a crappy PSU like this one has a chance at running a GTX 650. Barely.

Wow, I wonder if the Seasonic 350W is also a single rail.

BTW I've read posts on forums about various Dell computers where people say that Dell states that the limit of the motherboard is 35W or something like that. Is that really true, or does Dell base their limit on the power supply? Doesn't a PCIE slot HAVE to be capable of 75W or whatever the standard is? If they really are not meeting the spec, that would be a big downside for pre-built.

 

[Zap]

If the 350W version is not single rail and is a true dual rail, it likely would have one rail feeding the CPU (through the 4-pin +12v or 8-pin EPS plug) and the other rail feeding everything else including the 24-pin.

IDK about the Dell motherboards and how much power they supply through the PCIe slot.

 

[Alan G]

The other important factor is that Dell can specify and buy components much cheaper than we can. Their labor costs are much lower as well. For an ordinary office computer there is no way that a DIY rig can compete with Dell (or any of the other big manufacturers) on SFF units. That being said, I just finished a SFF computer for my wife. My build notes are below and I've posted a picture of the build on the Case Gallery Thread so you can see the issues that I faced. This was not a cheap unit with the component cost of about $600.

I found the new Lian Li PC-Q27 case especially appealing as it has nice clean looks and is the right size for her desktop. As one who has only built ATX machines, I faced an interesting task in terms of selection of components and the build itself. Since her computer is only used for MSFT Office applications, Internet, and occasional video streaming, I didn’t need to consider adding a GPU and would rely on Intel on chip graphics. Her office is upstairs and requires WiFi for connectivity. She is always complaining about boot time on her old computer so an SSD would be needed to hold the OS and core programs. In addition to the Lian Li case, the following components were selected (yes this is a somewhat ‘over the top’ build):


Gigabyte GA-H77N WiFi Motherboard
Intel 3225 i3 CPU
Samsung 120GB SSD
8GB Crucial Ballistic RAM
Western Digital 500GB Blue HD
Silverstone NT07 CPU Cooler
Seasonic G-360W PSU

Although there is room for an optical drive, I elected not to install one as she rarely uses one and it’s easy enough to connect a USB DVD drive if needed.


I knew the case was going to be small and selected the components accordingly. The case is passively cooled with warm air exhausted by the PSU whose fan is oriented facing the MoBo (it needs an ATX size PSU). Heat is likely not to be a problem given how this unit will be used. The combination of the Gigabyte MoBo and the case limit the choices of the CPU cooler. The cooler has to be less than 70mm tall and this MoBo will not take the small Noctua cooler because one of the coils interferes with the mounting. I originally put the stock Intel cooler in but had a MoBo failure as the DVI port died just after getting Windows installed. I was able to get the Silverstone NT07 pretty cheap which has a little better heat sink (I’m sure the Intel cooler is more than sufficient for this) and I believe that this is pretty much the only heatsink currently available in the US (Scythe does not currently sell in the US). A modular PSU would be preferable for this case but there are really no good ones available in the 350W range. I did see a Corsair 430W semi-modular case but didn’t need that much power. The Seasonic G-360 only has six cables which appeared on paper to be manageable since I would only need to worry about where to put the three unused cables.


There is a YouTube video of the case on the Lian Li website so I am not posting a picture of the empty case. The SSD drive can mount on the bottom of the case right below the railing that holds the data hard drive. Lian Li provide rubber grommets that lock both drives in place. I thought that I could run both SATA data cables behind the MoBo and under the HD drive railing but was disappointed to see that it would be impossible to install the SSD SATA cable because of its flush position and had to remove the MoBo since the SATA cables cannot be pulled through as there is not enough clearance for the connector head. The cable for the HD did stay behind the MoBo and there was no problem in connecting it. Because of the proximity of the two drives it was simple to use only one PSU cable that had two SATA power connectors though you have to install both the power and data connectors to the SSD prior to mounting it to the chassis.


There is no reset switch on the case (thank you Lian Li) so I only had to hook up the power switch, power LED and HD LED to the MoBo. I found out the hard way that one needs to tie the cable down to something so that it is out of the way when the PSU is finally put in (the PSU dislodged all the cables and the computer wouldn’t power up!). I ran it up into the optical drive bay and then back down so it was safely out of the way. All connections have to be done before the PSU is put in to the case as there is no access to the MoBo once this is done. You can see how the build looks just before the PSU goes in (the unused cables are tied with the blue Seasonic strap). It takes some care to feed the cables into the case so that they fit snuggly against the right front side. The PSU goes in horizontally. Although there is a slot for a video card, I think it will be challenging to put one in. Perhaps if only a single SSD drive is being used and one has a modular PSU it might work.


[FONT=&quot]I was pleased that the final build looked as clean as it could be. The PC is working fine with minimal fan noise and I cannot detect much if any heat being generated. This is a perfectly good case for a nice office PC and probably a home theater unit as well provided the right components are chosen. If money is not an issue, one can have a good deal of fun putting together an SFF computer.[/FONT]