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 Post subject: a64 psu advice
PostPosted: Tue Sep 28, 2004 2:13 pm 
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Location: Arlington, Virginia
I will likely want to get a more silent psu for a new system I am building, but I wonder if I could power it up using my old psu? It is an Enermax 351 (330W). Do you think it will support an A64 based system with +12V @ 12A?

EDIT: I suppose my question is really whether it is realistic to expect a 12A rated supply to work at all with a typical A64 system? Is it a reasonable figure? I noticed my mainboard spec says the supply must be 8A minimum but I have no idea what the A64 will draw on the 12V line.

Thanks,

Steve

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PostPosted: Sat Oct 02, 2004 8:31 am 
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Hey Steve, your post seems a little vague perhaps adding a few more details will get someone to jump in here.

Things like how many optical drives you are using, # of HD's, $500 video card with 10 power connectors, etc... See where I am going with this.

I dont know a whole lot about the PS loading issue myself but if nobody else throws in their ideas after adding some details. You could always do some math and look up the power draw for each of your components and guesstimate what kind of current your system will need.


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PostPosted: Sat Oct 02, 2004 1:46 pm 
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It'd really depend on your Video card or your planned video card. If you have a lightweight video card, that PSU should be able to handle it alright enough. But if you have anything more powerful than a Radeon 9600, you may want to get a PSU that can handle more 12V.

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 Post subject:
PostPosted: Sat Oct 02, 2004 4:33 pm 
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It depends on a bunch of things.

If the CPU was a mobile athlon64, it'll use less power, the same probably is true to a lesser degree for a wintchester. Underclocking/undervolting would also reduce power demand. Besides the number of hard drives, the type also makes a difference, spinpoints use a bit less each than Baracudas. Combo drives supposedly use more than their fair share of power.

For example, assuming you don't have a high power video card:
three cuda's would very likely overload that PSU;
one spinpoint, a low voltage CPU, and an optical drive which doesn't spin up when you turn on your PC should be fine.

You could check AMD's system building guides. For the CPU, make sure to take into account 12V=>1.**V conversion inefficiancy. Cuda's demand 2.8 amps of the 12V rail at spin up(boot), Spinpoints, 2.05 amps IIRC. My combo drive(which BTW does a quite good impression of a dremel) requires 1.3A of 12V, though your optical drive will likely differ.

Some people might find it stupid to choose your components to fit your power supply instead of the other way around, but if you do that, you'll at least have a system that doesn't demand much of a PSU, so even if you do decide to get a new PSU, at least it'll run quiter in that system than in a more power demanding one.


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PostPosted: Sat Oct 02, 2004 5:28 pm 
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Thanks everyone, MikeC and doing some further reading has helped me get a better idea of how much power is required. I will be patient and wait for my new psu. I still have components to get. I need to choose a case also.

It appears that the A64 will draw just about 8-11A and my current psu is to close to be comfortable. Besides, I will use it in the computer I build from leftovers.

I am looking at the dual rail Enermax 325 and the 300W Super Tornado for psu.

My silent PC has been a long time in coming. ;-)

AMD Sempron 3100 (Don't laugh, see below)
ASUS K8N
ATI9600XT
1GB Crucial 2 x 512MB sticks
120GB Maxtor
LiteOn 52xCDRW

possibly
20GB Maxtor or it will go in another machine with the old MB and Duron

Maybe a DVD burner.


I ordered a Sempron 3100 to see what it can do. I've had good luck with my Duron 850, which has held its own for a long time in everything I do except 3D games (my old Radeon 7000 based video does fine with most) and video encoding. I do get encode times relatively the same as the Mac our compressionist uses, so I am not expecting much of an improvement. I'm hoping that it might use a little less power than the A64. And there's not much 64 bit software out there yet.

I may get a Zalman AlCu or HT-101 for HSF. The CPU is OEM.

I'm getting a board that can take one of the regular A64 so if I want to replace it as prices come down, I can. I sorta want to try the Semperon because the low end A64 is now about what I paid for a K6200 some years ago.

The board is an ASUS K8N. I didn't want the extra garbage on the deluxe board. I have a nice Adaptec firewire card and will continue using it, so I don't need onboard firewire. And gigabit LAN is useless, since I don't have any other PC's with that. I am not that interested in the third-party SATA controller and will use the one on board. I don't need onboard sound (although it has it) and don't want onboard video.

EDIT
I have a 9600XT. The 9600XT is the most powerful graphics card that is still passively cooled. INCORRECT the 9600XT has a small fan mounted to a heatsink. It is not passive. But it's okay with me because I can't hear it over the case fans and I am not accepting any less than this level of performance.


I still love the minimalist design of my Inwin A500 case although it is beige and poorly designed for good airflow. So it is hard to decide on a case. I'm torn between trading a bit of quiet for a bit of style. I end up suffering from the Sonata/BQE syndrome as they are the same price at my local store.

This is a very new board. People don't know about it yet, they mix it up with MSI's. I apparently am one of the first in line to buy the Semperon 3100 because a lot of people don't know it is a A64 based chip. LOL I am on the bleeding edge of the trailing edge with this stuff. All this was pretty cheap, so I'm not worried about replacing it.

There are a lot of urban legends out there about the Sempron 3100. People don't realize it is a socket 754 CPU and that it is based on the A64. It has all the architectural features but without a 64 bit instruction set. It has Cool 'n Quiet. At least this is what I have read.

EDIT: I must have Semper Fidelis on the brain, Sempron, Sempron.


Steve

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Last edited by canthearyou on Thu Oct 14, 2004 10:13 am, edited 2 times in total.

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 Post subject:
PostPosted: Sun Oct 03, 2004 2:12 am 
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I think its the high price of the sempron 3100 that makes it currently an unattractive purchase. At least in Europe difference between sempron 3100 and fully featured a64 2800 is typically only around 10 euros.


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 Post subject:
PostPosted: Sun Oct 03, 2004 4:28 am 
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canthearyou wrote:
It appears that the A64 will draw just about 8-11A


Steve, that above comment is highly questionable. 11A@12V would give you 132W which is probably what your WHOLE SYSTEM power requirement is, let alone just the CPU or just the load on the 12V line.

Even if your Athlon64 was running at full power and drawing max rated power (ie 90W) - something I find very suspect - that would mean a near 6A load on the 12V rail.

The main 12V loaders are the HDDs on system start and the optical drives, again at startup. If your PSU can handle that load, you should be fine. Most quality PSUs should be able to handle the momentary extra draw at powerup.

FWIW, I ran a A64 3200+ (actually an overclocked 3000), plus two powerhog seagate sata disks plus a DVD writer with a 4 year old 300W Fortron PSU rated for 15A on the 12V rail. No problems.

Again, FYI, A64s undervolt VERY nicely. Even though my ABIT board doesn't allow undervolting in the BIOS, with a third-party utility, I've undervolted all the way down to 1.25V.

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 Post subject:
PostPosted: Sun Oct 03, 2004 6:12 am 
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burcakb wrote:
canthearyou wrote:
It appears that the A64 will draw just about 8-11A


Steve, that above comment is highly questionable. 11A@12V would give you 132W which is probably what your WHOLE SYSTEM power requirement is, let alone just the CPU or just the load on the 12V line.

Even if your Athlon64 was running at full power and drawing max rated power (ie 90W) - something I find very suspect - that would mean a near 6A load on the 12V rail.


The CPU does use the majority of the systems power. 90W/ 12V is 7.5A. And you can't just didvide the CPU's heat rating by 12V, the athlon xp system building guide mentions a conversion efficiency of 80%.

burcakb wrote:
FWIW, I ran a A64 3200+ (actually an overclocked 3000), plus two powerhog seagate sata disks plus a DVD writer with a 4 year old 300W Fortron PSU rated for 15A on the 12V rail. No problems.


That's a fortron unit, and it has 3 extra amps. And DVD writers for some reason(?slower spin) are supposed to use a lot less, not more power.


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 Post subject:
PostPosted: Sun Oct 03, 2004 12:33 pm 
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I also remember an AMD rep implying that the AMD thermal output was nowhere near that TDP mark. I'm making a wild guess here but I kind of got the feeling that the A64-3000 was something around a 75-80W CPU at max power.

I included the optical drive not because it draws a lot of power but because you might experience a powerup problem. At powerup, the hdds draw max power, and the optical drives all spin up at the same time.

For your comparison, I'll list what my rig ran on the old Fortron 300:

Athlon64 3000+ (overclocked to 2250 MHz @ 1.5V)
2x512 OCZ RAM (these babies run at 2.71V not your average 2.5 or 2.63V)
2x120 Seagate SATA drives (These gobble up 2.8A on the 12V line at powerup PER hdd, that's 5.6A just for the disks)
1xCDRW
Radeon 9700 (There are no power figures for this but since it's a similar card to the 9800 series I did a clock speed guesstimate for a 45W figure)

FWIW, the same setup had a problem powering the hdds with a 380W Antec PSU with 16A on the 12V. That's more power on the 12V than the Fortron, but the hdd pull was too much.

Again, 12A is pushing it but it might also work. The 9600XT is nearly half as energy consuming as my 9700 plus it draws max current from the 3.3V on the AGP, not the 12V line. He's also got one less drive to worry about, which is really the only real problem.

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PostPosted: Sun Oct 03, 2004 1:04 pm 
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Thanks Dobby, yes, it is within about $10 or so of the A64 2800 OEM (except that newegg dropped it by $12 since then). I didn't realize the 2800 had fallen that low. I think the 512K cache would be the most immediate benefit. Right now, my Duron runs nearly all apps, so I think whatever I use will be more than enough until all the changes coming in the PC platform are debugged. I generally agree that it is not as great a deal as Duron was.

The 12A was with the A64 at full load and derived from averaging everything I read. Again somone in a discussion group claimed they measured 11A at full load, but who knows how they came by that. That would be at maximum dissipation. I think it must draw on average 7A given ASUS specifies a minimum of 8A @ 12V to the board.

For the Sempron 3100 AMD says

TDP is 62W Max P-state

I do not know what that means exactly, but I expect it is the max power state.

The 2800 shows a TDP of 89W Max P-state

So maybe the Sempron runs cooler. It might be worth it for that.

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PostPosted: Sun Oct 03, 2004 2:55 pm 
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canthearyou wrote:
For the Sempron 3100 AMD says

TDP is 62W Max P-state

I do not know what that means exactly, but I expect it is the max power state.

The 2800 shows a TDP of 89W Max P-state

So maybe the Sempron runs cooler. It might be worth it for that.


Good point, it should be like the heat difference between a thouroughbred and a barton, and from what I've heard, hammers aren't as affected by amount of cache as XP's

Edit: One more potential benefit from semprons, unlike regular hammers, semprons aren't available at above 1.8 ghz, and if AMD is producing semprons of equal quality/variation as hammers, then you might get a chip that can overclock a good amount at stock voltage, or undervolt at stock speed.


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 Post subject:
PostPosted: Sun Oct 03, 2004 8:45 pm 
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canthearyou wrote:

So maybe the Sempron runs cooler. It might be worth it for that.


In most of the current benchmarks Sempron lands very close to the a64 2800, so I admit question which to choose is rather academical. Cooling point is a good one and when you get system up and running, please share your experiences. There's very little information yet available how socket754 semprons will do in "real life". :)


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 Post subject:
PostPosted: Mon Oct 04, 2004 11:12 am 
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Yep. I'll see what it does. The lower TDP was what tipped the balance on Sempron over A64 until there is more 64bit software available. Undervolting might be something to try. Supposedly the ASUS board can do that.

I picked up a BQE. So that's decided. I wanted better airflow, more room and prefer the 90* cage. So far I expect HD temps will be about the same as I have now from reports here. It is a compromise.

Steve

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 Post subject:
PostPosted: Thu Oct 14, 2004 10:15 am 
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BTW the 300W Super Tornado is doing fine so far as supplying power with the current setup.

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