How much 12V amps needed for Athlon 64 X2?

[h2ospa]

(There is no P4-era sub-forum, so I am posting this question here)

I recently obtained a Socket 939 motherboard (Gigabyte GA-K8NF-9 rev 1), and a Athlon 64 X2 processor (3800+). The motherboard is interesting to me because it was probably one of the last few motherboards with dual floppy drives support. How often do you see a motherboard with pci-e slots AND dual floppy drives support? (Yes, I am obsessed with motherboard with dual floppy drives support)

But I have been trying to figure out how much 12V amps are needed to power it.

I have been using a 450W ATX power supply with 18A 12V output to power my P4 motherboard & Northwood 2.6GHz processor, and it is working just fine. But the same power supply won't power the Athlon. With only the motherboard and the processor, it just won't POST. I tried few other power supplies with 18A 12V output and none of them work either. Then I got it POSTed after I switched to a newer 450W power supply with 32A 12V output.

18A and 12V is 216W. I am pretty surprised that 216W isn't enough to power an Athlon 64 X2.

Please advise. How much 12V amps are needed to power the processor (and the motherboard, if that matters)? And where can I find out the power requirement of a processor?

Thanks in advance.

 

[Chuck(G)]

Were these name-brand power supplies? Off-brand Chinese ones often play fast and loose with nameplate ratings.

 

[h2ospa]

Were these name-brand power supplies? Off-brand Chinese ones often play fast and loose with nameplate ratings.

I wouldn't call them name-brand power supplies, but I collected those from name-brand desktops, and tested them to make sure they are standard ATX power supplies, not those brand-specific fake ATX ones like Dell or HP.

 

[Chuck(G)]

I'm running a 939 system here with 2 hard drives and a single-core Athlon 64 (don't recall offhand which) with what is a 450W PSU and 4GB memory. Motherboard is an ASUS A8N-SLI from an HP desktop. Nothing to write home about, other than the onboard floppy controller being FM-capable.

Are you running a high-end GPU with yours? Those can suck on the +12 pretty hard.

 

[h2ospa]

I'm running a 939 system here with 2 hard drives and a single-core Athlon 64 (don't recall offhand which) with what is a 450W PSU and 4GB memory. Motherboard is an ASUS A8N-SLI from an HP desktop. Nothing to write home about, other than the onboard floppy controller being FM-capable.

Are you running a high-end GPU with yours? Those can suck on the +12 pretty hard.

Not at all. Just a very basic pci-e nvidia video card Quadro 580 for basic DVI display. I wouldn't even call it a graphics card. And that's after the non-POST. Originally I didn't even have a video card plugged in.

 

[Chuck(G)]

I suspect that there's some exaggeration in the specs for your PSU, in that case. I run AM3 quad core on a 450W-rated PSU (Seasonic) without issues. The last time I looked for a dual-core 939 CPU on eBay, I was taken aback a bit at the prices being asked.

 

[h2ospa]

I suspect that there's some exaggeration in the specs for your PSU, in that case. I run AM3 quad core on a 450W-rated PSU (Seasonic) without issues. The last time I looked for a dual-core 939 CPU on eBay, I was taken aback a bit at the prices being asked.

How much 12V amps does your power supply supplies, according to the label?
I think that is the difference between the working one and the non-working ones I have.

 

[Chuck(G)]

I did find this handy chart for my motherboard:

 

[h2ospa]

I did find this handy chart for my motherboard:
View attachment 1281013

That probably explains it. I wish all motherboards and processors have these specs in the manual.

Thank you.

 

[bakemono]

I run an X2 4850e off a 185W flex-ATX PSU.

 

[Unknown_K]

https://www.cpu-world.com/CPUs/K8/AMD-Athlon 64 X2 3800+ - ADA3800DAA5CD (ADA3800CDBOX).html

That is an 89W TDP CPU. It runs on 1.3V so it could be using the 5VDC and not the 12VDC rail to make that voltage depending on the motherboard. Older supplies had most of their power in the 5VDC section while modern supplies have all their power in the 12V rails (mostly for GPUs). So, all 350W supplies (for example) are not equal when powering old systems.

 

[GiGaBiTe]

https://www.cpu-world.com/CPUs/K8/AMD-Athlon 64 X2 3800+ - ADA3800DAA5CD (ADA3800CDBOX).html

That is an 89W TDP CPU. It runs on 1.3V so it could be using the 5VDC and not the 12VDC rail to make that voltage depending on the motherboard. Older supplies had most of their power in the 5VDC section while modern supplies have all their power in the 12V rails (mostly for GPUs). So, all 350W supplies (for example) are not equal when powering old systems.

By the Athlon 64 era, no motherboards were still using the +5v rail to power the CPU. That switch started happening back in the Athlon XP era, by the time the late Athlon XP chips came around, most motherboards being released were using the +12v rail for the CPU.

 

[Chuck(G)]

I have a couple of hard-drive molex 4-pin-to-ATX12V 4-pin plugs. Never found a PSU with enough moxie on the regular 12V rail to be of any use to supply +12 to the CPU. (Socket 754 mostly)