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AMD power requirments

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{PMS}fishy

Senior Member
Joined
Dec 20, 2001
What are the minium and I mean minium power requirments for an AMD system.

T-Bird 1.4, CD-Rom, NIC, HDD, SDRAM, AGP video
 

madsam

Member
Joined
May 3, 2002
Location
New York
my friend runs a 300, or a 350 watt bargain psu he bought locally, and his system is similar, but he's got a 1.33 t-bird, and a gf4....
 

juliendogg

Member
Joined
Nov 29, 2001
Location
NC, USA
i guess that would depend on who you ask, most say 300 is the absolute bare minimum, i've been running my setup (xp 1600, kt266a, one hdd, cdrw, dvdrom, agp vid, nic, and several fans) on an ancient 250w. runs fine unless i push the o/c too far, then the 5v rail drops below acceptable levels and i get some nifty reboots and other wierdness. the psu is not something to skimp on, get at least a high quality 350w imho. i'm shopping for a new one but i'm goin to go on and get somethin around 500w, vantec stealth is lookin mighty nice:D
 
OP
{PMS}fishy

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
Come on guys you are killing me. I have that same set up going on 200w right now. It needs to be as small as possible, as I am cramming it into one of those little IBM netvista cases. 4"x12"x13" I have 2 90w PSUs that I might try to hook together.
 

deathstar13

FSB FRIEK
Joined
Dec 24, 2001
im useing a 300 premier "generic" i cant wait till it dies!
but i have run it on a decent 250wt.
it seems ok at stock voltage my probs start when i oc. so mabey u wont get as much oc out.
 

The Coolest

Senior Member
Joined
Jul 29, 2001
{PMS}fishy said:
Come on guys you are killing me. I have that same set up going on 200w right now. It needs to be as small as possible, as I am cramming it into one of those little IBM netvista cases. 4"x12"x13" I have 2 90w PSUs that I might try to hook together.

You may just be squessing every last drop out of that PSU, and it just might die on you and in the worst scenario take some hardware with it, I strongly suggest you upgrade the PSU. It might seem its running ok, and it will untill the PSU just simply dies. I read many times of 250watters dieing when using on AMD chips...
 

ChillPhatCat

Member
Joined
Sep 5, 2002
Location
Ballston Spa, NY
Bah, I'll be running a 1600XP soon... 500W PSU :)

Eventually I do plan on a 333FSB 2800-3200XP... watercooled o course...


Personally, I wouldn't try to run less than 300W...
 

PCphreak

Member
Joined
Jul 9, 2002
Location
Dayton, Ohio
{PMS}fishy said:
What are the minium and I mean minium power requirments for an AMD system.

T-Bird 1.4, CD-Rom, NIC, HDD, SDRAM, AGP video

Aside from AMD recommended requirements, let's look at what your system is roughly asking for.

With a PSU, there are two ratings you want to look at. One rating being most important: Combined 3.3 & 5v wattage. The 12v wattage is second in importance. Again, *combined* 3.3 & 5v wattage is most important. The 'combined rating' for the 3.3v & 5v rails should only be looked at regardless of their actual individual rating. The reason is because the 3.3v and 5v rails are on the same regulation circuit. This means you can't draw the max amps simultaneously on both lines, but must keep the total combined draw between the two at the 'combined rating'.
You'll see why the combined rating for the 3.3 & 5v is most important when you look at how much power really gets drawn from it.
Here's a very basic list of max amp draw on 5v rail:
Mobo - 5a
CPU T-bird 1.4- max 40a
PCI - 2a each slot
Drive Logic (IDE & Floppy) - .5a to 1a each drive

AGP can draw up to a max of 110 watts...newer 4x cards signal using 1.5 volts instead of 3.3v- but are still powered off the 3.3v rail. Average your probably looking at 50 watts or less for a typical AGP card.
I'm not sure how much max power SDRAM will draw, but maximum your current setup will require a maximum of 49 amps on the 5v without the RAM....would this ever occur?....very very unlikely, because generally components never draw anywhere close to the max spec.
I would guess your pulling 100 watts or less on the 5v and 3.3 v rails with your system- based also on using an old/slow AGP card. With moderate use, your T-bird will cause a bit more of a load.
I'm not going to get into 12v power usage, because it's really negligable. Most fans draw about .1a and HDD motors draw about 1a after spin-up.
So W I T H O U T heavy usage, you could probably pull it off with a decent 250 watt PSU. A decent power supply will have a strong 3.3 & 5v combined rating.

-PC
 
OP
{PMS}fishy

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
The Coolest said:


You may just be squessing every last drop out of that PSU, and it just might die on you and in the worst scenario take some hardware with it, I strongly suggest you upgrade the PSU. It might seem its running ok, and it will untill the PSU just simply dies. I read many times of 250watters dieing when using on AMD chips...

I have been running on it for 6 months now.
 
OP
{PMS}fishy

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
Re: Re: AMD power requirments

PCphreak said:


Aside from AMD recommended requirements, let's look at what your system is roughly asking for.

With a PSU, there are two ratings you want to look at. One rating being most important: Combined 3.3 & 5v wattage. The 12v wattage is second in importance. Again, *combined* 3.3 & 5v wattage is most important. The 'combined rating' for the 3.3v & 5v rails should only be looked at regardless of their actual individual rating. The reason is because the 3.3v and 5v rails are on the same regulation circuit. This means you can't draw the max amps simultaneously on both lines, but must keep the total combined draw between the two at the 'combined rating'.
You'll see why the combined rating for the 3.3 & 5v is most important when you look at how much power really gets drawn from it.
Here's a very basic list of max amp draw on 5v rail:
Mobo - 5a
CPU T-bird 1.4- max 40a
PCI - 2a each slot
Drive Logic (IDE & Floppy) - .5a to 1a each drive

AGP can draw up to a max of 110 watts...newer 4x cards signal using 1.5 volts instead of 3.3v- but are still powered off the 3.3v rail. Average your probably looking at 50 watts or less for a typical AGP card.
I'm not sure how much max power SDRAM will draw, but maximum your current setup will require a maximum of 49 amps on the 5v without the RAM....would this ever occur?....very very unlikely, because generally components never draw anywhere close to the max spec.
I would guess your pulling 100 watts or less on the 5v and 3.3 v rails with your system- based also on using an old/slow AGP card. With moderate use, your T-bird will cause a bit more of a load.
I'm not going to get into 12v power usage, because it's really negligable. Most fans draw about .1a and HDD motors draw about 1a after spin-up.
So W I T H O U T heavy usage, you could probably pull it off with a decent 250 watt PSU. A decent power supply will have a strong 3.3 & 5v combined rating.

-PC

Thanks that tells me really all that I need to know.
 

TheOneDonRamon

Registered
Joined
Jun 8, 2002
Location
Richmond,Va
look at my specs..and been on it for a while..my lee7 uber 300watt psu pwnez you all..im gunna add a floppy drive..i hope my psu wont overload.. lols :/
 

papounet

Member
Joined
Aug 29, 2002
Location
Brussels
Re: Re: AMD power requirments

PCphreak said:


..
Here's a very basic list of max amp draw on 5v rail:
Mobo - 5a
CPU T-bird 1.4- max 40a
PCI - 2a each slot
Drive Logic (IDE & Floppy) - .5a to 1a each drive

.....
With moderate use, your T-bird will cause a bit more of a load.
I'm not going to get into 12v power usage, because it's really negligable. Most fans draw about .1a and HDD motors draw about 1a after spin-up.
-PC

dear PCphreak,
I am afraid that the CPU is fed from the 12V line

dear {PMS}fishy

please check the total budget equation in the AMD doc
http://www.amd.com/us-en/assets/con..._docs/26003.pdf
It includes typical values for most things you plug into the PSU

see the full series of post in http://forum.oc-forums.com/vb/showthread.php?s=&threadid=131426

see the full series of post in http://forum.oc-forums.com/vb/showt...922#post1118922


Most peole recommend overlarge PSU because overlarge PSU are said to be less prone to volatge irregularities.

What you are looking for is high quality low power PSU (250W because of the high requirement on 3.3V+5V combined regulation , good point from PCPhreak),
smaller PSU won't have enough of that, bu they would have more 12V that you care for.....

good luck
 

The Coolest

Senior Member
Joined
Jul 29, 2001
Well... I've never heard of the CPU running off the 12v. what's the point in that? it means most of the voltage will be wasted as heat on the convertion process and only heat things up. I can pretty much proove it, the faster you get the CPU, even if u'r not overclocking, just upgrading. I have a really bad PSU in my other machine, and I went from a 900 duron @ 1076 to a 1200 tbird at 1211mhz, so this can' be really counted as OC, as its only 1% more than ''stock".. I had the 5v line drop every time I changed CPUs, from 600 stock to 1076 (900) overclocked. the faster the CPU the more watts it requieres to run, the more drained the +5v line becomes. the +12v line haven't moved much at all, whilst the +5v droped from 4.87v (600 stock) to currently 4.73-4.76v (1200 @ 1211).
 
OP
{PMS}fishy

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
I know the CPU is either driven off the 5v or the 3.3v not the 12v. As the 3.3v and the 5v are on the same circuit, they both tend to drop as you push the CPU further and rasie the v-core.
 

PCphreak

Member
Joined
Jul 9, 2002
Location
Dayton, Ohio
Re: Re: Re: AMD power requirments

papounet said:
dear PCphreak,
I am afraid that the CPU is fed from the 12V line

Current VRM (Voltage Regulator Modules) accept anywhere between 4 to 36 volts input. It's really up to the motherboard designer as to how the VRM IC will be configured. The question regarded an AMD® Athlon based system, and currently AMD® based boards power the cpu from the 3.3/5v rail. Intel® is a different story, since they power the CPU from the 12v rail provided by the ATX 12v connector. The reason for sourcing the power from the 12v, is because the amperage dependencies are lower at a higher potential at a given load. In other words, you draw less current from the supply powering the VRM at 12 volts than you would at 5v.
Example:
70 (watts) / 12 (volts) = 5.8 (amps)
70 (watts) / 5 (volts) = 14 (amps)


-PC
 
Last edited:

papounet

Member
Joined
Aug 29, 2002
Location
Brussels
dear PCphreak,


thank you for your remark on Intel using 12V and AMD using 5V.
I am quite interested by your experience of failing 5V line when overclocking/overvolting CPU

I beg to differ nonetheless, as I based my remark on AMD processor using 12V converted down by VRM on the table 2 page 11 of Builders Guide for Desktop/Tower Systems http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26003.pdf

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26003.pdf

I beleive table 4 answer {PMS}fishy 's question
 

PCphreak

Member
Joined
Jul 9, 2002
Location
Dayton, Ohio
papounet said:

I beg to differ nonetheless, as I based my remark on AMD processor using 12V converted down by VRM on the table 2 page 11 of Builders Guide for Desktop/Tower Systems http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26003.pdf

Thanks for posting the chart. I really have no other explanation for AMD® showing the CPU being powered from the 12v rail, other than the fact that it can differ from one motherboard manufacturer to another on what the input voltage will be to the VRM. It can be 5v or it can be 12v. I think the next step in finding an answer is emailing a couple motherboard makers and see what their process is. Sooner or later, I personally feel every motherboard maker will impliment 12v or higher in powering the VRM....
I'll see if I can't find some contacts and let you all know any results...

-PC