Enough power for an Athlon XP 1600?

[Deanodarlo]

Thinking about getting an XP 1.4Ghz 1600, but I'm not sure if my PSU can handle the strain. Here are the 300W specs:

Output specification :- +3.3V = 14A, +5.0v = 30A, +12.0v = 10A, -12V = 0.8A, -5V = 0.5A, +5VSb = 2A.

(+5 and +3.3v total output 165W)

Looked at the tech docs and an XP 1600 uses a max of 34A and an average of 30A. Does the CPU draw its current from the 5V line? Or a combination of the 3V and 5V?

Will I be able to run an XP on a 165W combined?

 

[Goi]

Those specs are below what AMD recommends, but who knows? They might work, but if I were you I'd get another PSU. According to what AMD recommends, a 300W PSU should have the following ratings(max continuous ratings):
+3.3V = 28A, +5V = 30A, +12V = 15A(peak 18A), -12V = 0.8A, +5Vsb = 2A(peak 2.5A), -5V = 0.3A.

Most older PSUs don't meet this recommendation, especially for the +3.3V, even some of the newer ones only offer around 20A.

The Athlon XP draws its current from the +12V rail, and it only draws less than 7A, rather than 30-34A as you mentioned. However, your drives and fans also draw power from the +12V rail, and if you have some high power ones, you might exceed the 10A rating of your PSU.

As for your +3.3V rail, its used by memory, AGP graphics cards and the motherboard itself.

 

[FishTankX]

Hehe.. the AthlonXP does draw 30-34 AMPs, GOI. But read carefully.

1.75 VCore*34 amps=60 watts
You're 7 AMP figure*12 volts=85 watts (Close! You might loose some power in the serious stepdown from 12 volts to 1.75 volts)

As your your 12 volt rail not making it.. i'd seirously reccomend you to stick to a single harddrive. That would keep you in the green for power. As they draw power offa the 5V and 12 volt rails, you'll probably be safe. But you'd be pushing the limits of your power budget. And if you decide to upgrade to a 2100+, well...


If it's possible, you could use an old cheap AT powersupply (plugged into the female connector on your ATX powersupply) somewhere on the bottom of your case to power drives, and maybe even the CDROM, and fans.

 

[Goi]

I said below 7A, not 7A, the Athlon 1800+ actually draws around 6.87A from the 12V rail for a power consumption of 82.47W, so the Athlon 1600+ should be drawing perhaps around 6.5A or slightly more. I was talking about current draw from the 12V rail, which is what's important here, rather than its direct current draw from the "step-down"ed 1.75V supply

 

[Deanodarlo]

Thanks for the info. Fair amount of heat is produced by 60W ? I think I'll need a new cooler as well.

Just to clear things up then, where does the power for the CPU come from?

EDIT
I know you both mention stepping down the 12V(*10=120W) line to feed the CPU, but why then do AMD always mention the 5V and 3V rails as being important?
EDIT

In fact what powers what from the PSU?

My Guesses:

5V and 12V lines for drives?

3V lines for AGP cards and PCI devices and RAM?

3V and 5V combined for CPU and motherboard? (wrong because you guys say it's a stepped down 12V)

To make it even worse, I've heard some motherboards only draw current off the 5V line for all components instead of using both the 3V and 5V. Like certain Epox boards for example. My 3-phase power hungry 8KHA+ may be one of those.

Can you guys help set my mind straight for the future.

 

[Goi]

In general:
+3.3V = AGP graphics card, motherboard, PCI NIC, PCI soundcard, some memory, PCI SCSI card
+5V = memory, FDD, CD-ROM, CD-RW, DVD-ROM, motherboard, HDD, P2/P3 CPU, memory
+12V = fans, CD-ROM, CD-RW, DVD-ROM, motherboard, P4/Athlon CPU

Check out this for more info

 

[Deanodarlo]

Thanks, MUCH appreciated.

 

[Deanodarlo]

For anyone who is interested, this table I've ripped from Goi's link is really useful.

PSU current guide

 

[Deanodarlo]

Well to be safe I grabbed a XP 1500 secondhand and VERY cheap - works without any issues whatsoever.

The voltages are all fine, exactly the same as with my Duron 800. I used to run the 800@950 unlocked on a 133 FSB and had no issues back then.

First thing I did was to raise the FSB to 140. Great thing about a 10 multiplier is the maths is easy and I'm now running 1400Mhz trouble free. Again no drop in voltages. Looks like this Macron 300W can handle low end XP's fine, even with all my hardware in my sig.

Had to add a case fan to the back of my ATX case however . The extra noise is driving me mad.

Before I just had the PSU, motherboard and CPU fan running and everything was real quiet. Temps on my Duron 46-53 C full-load on the coolest to warmest days respectively

With the XP, the Duron config will of had temps of 53-62+C full load depending on the ambient temp. Added a case fan to the rear and the temps are 41-49, a drop of 10C. How do you guys cope with the sound?

Finally some advice guys. I'm not unlocking this CPU (perhaps in the future when it becomes my back-up rig) so where is a safe bet to run the FSB?

Since this is my main serious rig, I want the extra performance since I've stuck this noisy fan in now but with minimum risk.

I was thinking about sticking to 140FSB. The PCI is only 2Mhz out of spec (35) and the AGP a modest 70Mhz. At this speed the XP needs no extra voltage (Checked Prime95) and the temps are still in the low 40's. Crucial RAM still at the 2.6V mark and fastest settings used.

What do you think?

 

[Goi]

Well, the limit is really for you to find out. There's no way we can tell you since we don't have such good prediction abilities
What stepping if your 1500+ though? It would be easier to try and tell if we knew that.

 

[Deanodarlo]

I didn't write down the stepping, I was so eager to get the cpu slapped in. The chip is about 6 months old.

I'm not really bothered about the cpu or system limit, more what you guys thing is a safe(er) area to run in. Like you said, only I can find the maximum potential of this setup. I know this RAM will run up to 166 at 2.9V, 160 at 2.8V and 150+ at 2.7V. It?ll do most the 140?s with 2.6.

I'm torn between ramming the FSB up to the limit of the locked CPU, probably around the mid to high 140's OR playing it safe - 140 FSB, 35 PCI and 70 AGP isn't really pushing very hard.

Decisions, decisions?????.

 

[Insane3D]

The Athlon XP draws its current from the +12V rail

IIRC, the Athlon's pull heavily from the +5v rail, not the +12v rail. This is why a good deal of boards have trouble keeping the +5V rail voltages up. The P4 uses the +12v more, which is why they use a seperate +12V connector. There was a discussion about this when some of the newer Athlon boards started showing up with the extra +12v connector. Ever watch the rails of an Athlon under load...the +5V really takes the hit, not the +12v.

 

[Goi]

Well, I guess you remembered incorrectly then. The Athlon XPs, as do the Athlon Thunderbirds, draw their current from the +12V rail rather than the +5V rail, that much I'm sure

 

[Deanodarlo]

Now running this 1.33 1500 XP @ 1.50 on a 150 FSB.

No voltage increase has been needed on the CPU - it's still at the 1.75 default and temps are 50C max under full load.

Prime95 been running for over an hour - no problems.

Is it safe running 150 FSB?

 

[Goi]

That's a pretty decent overclock. Your temperature readings are pretty good especially since that's under load. I would run Prime95 for at least 24 hours, and if there are no problems then it should be fairly stable at that speed at least.

 

[Deanodarlo]

I'm getting the feeling that this 1500 XP is a marked down 1700 or something. This sometimes happens when AMD get good yields of high performance XP's - they have to mark some of the better performing chips down to satisfy the market.

Since I haven't had to increase the voltage and the temps are fine, this XP will probably do 1600 Mhz if my PSU was up to it. Unfortunately, voltages are starting to get shaky at 1500. Plus I don't fancy my hardware on a 160+ FSB with a 1/4 divider.

Still, when this chip is no longer my main rig I'll have a go at unlocking it in the future.

Kind of reminds me of those Duron 600's that would do insane speeds, while the Duron 900's were reaching the limit of the core.