Well, I've tried a couple of power supplies now, and while it's been fun, it hasn't exactly been cheap. So I need some advice: what power supply will run quietly in a dual Athlon 1700+ plus rig? The two power supplies I've tried are:

Zalman 300APF
Seasonic Super Tornado SS-300FB

I think both of these power supplies would be great in a "normal" computer. In mine, when I turn the system on it's whisper quiet. However, by the time I've gotten into windows the fan speed has ramped up and stays up. The Super Tornado fan speed varies from a loud hum to a very loud hum + air rushing noise (depending on system load), while the Zalman is more steady but just plain loud. I'm thinking that I might need to move to a higher-rated PSU?

Anyways, if any of you dual Athlon users out there have found a quiet power supply, or have successfully modded a loud power supply to be quiet, please let me know! (I'd try modding these power supplies, but I'm scared because I've burnt up a couple power supplies before and those were in single processor systems. I did read the "quieting a dual Athlon MP" article, and while the Antec with the 18CFM fan worked for Leo, he had ducted the exhaust from his CPUs directly outside the case, which would lower the temperature of the air in the case by a lot. I don't really want to have to go through that kind of effort. Plus, I'm pretty sure an 18CFM fan in my Zalman PS would cause almost spontaneous combustion in my system...)

Here are my system specs, in case it makes a difference (pretty typical though, I think)

2x Seagate Barracuda IV's
ATI FireGL Z1 (equivalent to Radeon 9500 in terms of power draw)
2x AMD Athlon XP 1700+ (volcano 9 heatsinks w/Panaflo L1A's @ 7V)
512MB RAM
Tyan Tiger MP
Plextor 16x10x40 CDRW drive
Pinnacle DV-500 video capture/editing card
Soundblaster 128 PCI
2 ethernet cards
3 panaflo L1A case fans @5V

Oh, and one more thing...the power supplies were loud even with the side of my case removed and a pretty low room temperature (I feel cold in my room...my Dad keeps the heat cranked way down). So the problem seems load-related and not airflow-related.

Hi Legacy,

I run a similar system: Two XP1600+ Palomino's on a Tyan Tiger MP board. I have an Antec SX-840 case (like Powergyoza's, but without the door). Other system components: Geforce3, SP1614N hard drive, and the other standard stuff.

Powergyoza didn't actually duct his CPU's, he just gave the PSU a separate compartment for airflow. This is really easy to do. I just took the top 5 1/4" bay cover out, ripped the cover off a spare 8x11" notebook, and jammed it into the case right below the PSU. This is all it takes to duct a PSU, assuming your case has no front door. I also ducted the CPU's to the back of the case using some vinyl dryer duct. This took 20 minutes and allowed me to remove the case fans.

Anyway, I know you asked about power supplies, so I'll talk about them now. Both PSU's you mention are only spec'ed to provide 30A on the 5V rail, and because you're using that silly Tiger MP, you probably get close to (or exceed) that rating on a regular basis. See this thread for more info. I use a 400W Antec PSU, rated for 40A on the 5V rail. The PSU makes almost no buzzing sound. I replaced the fan with an undervolted Panaflo, of course.

If you had any other dual-Athlon motherboard, those PSU's might have worked perfectly. But us Tiger MP users have fewer choices because the board only uses power from the 5V rail for the processors.

That's great!! I'm so excited...it IS possible to have a quiet duallie without too much effort! I just have a couple more questions, based on your reply...which Antec 400W power supply are you using? There doesn't seem to be a 400W Truepower supply...there's a "solution series" SL400 and a PP403X...is it one of those? And you ducted your CPUs...that means the fans are in "suck" mode on the heatsinks right? What fans/heatsinks are you using? And does the duct just go to the fan vents on the back of the case? Are there fans there as well to help pull the air through? And what voltage are you running your PSU fan at? Is it wired to the internal fan header or a connector outside of the power supply?

The (originally 2-fan) power supply I have now is the SX400. My previous one was a PP-403X, I think. Both said they could handle 40A. Antec's older PSU's were rated to 40A, but the newer ones only say 35-38A, since PSU's nowadays are built to accomodate high current on the 12V line. They might still work, though. The 400W Sparkle/Fortron is also rated to 40A, but I've never used it.

I tried both ducted CPU fans in suck, both fans in blow, and one in each mode. I decided to leave the bottom CPU in blow mode (pulling air in and onto the heatsink) and the upper in suck mode (pushing air out of the case). This keeps the CPU's reasonably cool, and it helps get rid of the exhaust air. The other fan configurations caused trouble elsewhere in the computer. My VRM2 temperatures were going through the roof (90C, ouch!) when I had both fans sucking, and case temperatures (which I gauge by the DDR temps) went up several degrees when both fans were blowing. However, my configuration might not be the best one for you! I just got fed up with the stupid heatsink fan clips, and so I'm done tinkering.

To install the ducts, I cut a piece of vinyl duct, jammed one end through the cut-away fan grill in the back of the case, and wrapped the other end around the CPU fan. I'm using SK-7 heatsinks, so the fan clips go over the end of the duct to hold it in place. It's a real pain to get those clips in place.

I have no fans on the back of the case to assist the CPU fans. Case fans do help, though: when I removed the case fans from a cardboard ducting experiment, I had to raise the voltage of the CPU fans by 0.5-1V to bring the temperatures back down to where they were before. But since the CPU fans are buried inside the case, they don't make much noise, so I left the case fans out.

All fans are 80mm Panaflo L1a, rotated 90 degrees, because they make the least amount of noise when their label reads from bottom to top. Here are my fan voltages: 5V decouple-mounted in the lower-front, blowing on the suspended SP1614N hard drive (temperature: 31C). 5V mounted with a Zalman fan bracket over the Geforce3 video card, whose heatsink has been replaced with a big copper thing (temperature: luke-warm to warm, never more than 50C). The CPU fans are wired through a Fanmate, and I usually leave the blow-fan at 6.5V and the suck-fan at 7.25V. This gives me idle CPU temperatures of 56C and 59C, respectively. (Wow, the Panaflo is really good at blowing air straight down!) Load temperatures when encoding a bunch of MP3's, two-at-a-time, are something like 59C and 63C. Raising the fan voltages by 1-1.5V brings load temperatures back to idle levels. All temperatures are read though Tyan System Monitor, and ambient temperature is about 23C.

The PSU fan runs at 6.5V, wired through a Fanmate and plugged into the motherboard. The fan is mounted on rubber thingies on the outside of the PSU, with no grill, and any air gaps between the fan and the PSU covered with electrical tape. The PSU fan circuit is useless in my model, since it ramps up to 11.5V after 10 minutes, no matter what I do. The fan circuit in the Sonata's PSU, and perhaps the one in Antec's other new models, is more sensible, and it might be worth using. The PSU exhaust air temperature varies wildly from 30C to 45C, depending on where I place the temp probe and whether I'm loading the system. A good way to test the PSU temperature is to put your hand on the top of the PSU's case: if it's hot, you need more airflow. But the Antec PSU's are pretty durable: I almost burned my hand on it once when I forgot to plug the fan in!

My computer setup probably isn't ideal for you. It's not very pretty-looking, it is custom-tailored to my case, and it makes compromises that you may not be comfortable with. I hope I've given you some ideas, though.

If you do buy another PSU, I really hope it works! Before you make another purchase, try disconnecting individual components from your computer: the hard drives, the video card, the other expansion peripherals. Maybe even remove one of the CPU's. A certain component could be giving your PSU trouble. There's a thread or two on SPCR about Barracuda's causing PSU's to whine or buzz, for example.

Good luck! Thanks for reading this far!

Wow, thanks for all the info! All things considered, I think I'm going to try the SilenX 400 watt power supply. I looked at the Super Silencer 400, and that only provides 30A on the +5V line (it's optimized for 12V line wattage). I also tried to find a power supply called the SX400, but I couldn't find any info on a power supply with that name from any manufacturer! (Unless you're referring to the SilentX 400...but that doesn't have two fans.)

I'm thinking about how I can duct my CPUs out of my case, but nothing simple comes to mind. I only have one fan vent at the back of my case, as well as some vents along the sides. I may try cutting extra holes in the case and running ducts to those, but that's only if I have trouble with getting the silenx PSU to run quietly. Although, according to the review, when the fan is at max in that PSU it's quieter than a Panaflo L1A at 12V, so I shouldn't have any trouble. Unless it overheats and shuts down...

I don't think there are any non-fan noises coming from my PSU, so I won't bother checking for devices that might be causing noise. Thanks for the suggestion though.

I'll let you know how it goes. I guess I'll be putting my Zalman and Seasonic up for sale soon. (I'm in the Toronto area...anyone interested? Hehe...)

Okay, I decided to pull out all the stops. I ducted my power supply just as you suggested by putting a big piece of cardboard (thin cardboard) underneath the psu and opening the top 5 1/4" bay of my case. I then removed the super tornado and put the Zalman back in, but fan-modded it with a Panaflo running at about 7-8 volts. I then cut the fan "grill" (more like a bunch of holes in a roughly circular formation) out of the back of my case and mounted a Panaflo @7 volts.

My computer is quiet! Well, quiet enough for me. I can't hear it when I'm playing music softly anymore, which is great. The exhaust temp of my PSU doesn't feel much hotter than before the ducting, when the original full-speed fan was in it. My internal temps have shot up, but I think they're safe...maybe someone can verify that for me:

CPU 1: 60
CPU 2: 70 (I read that the max operating temp for these CPUs is 90 degrees C, so I figure 20 under should be safe?)
VRM2: 73 (this one I'm really not sure about)

and the rest I'm pretty sure are fine. These are temps under load (running SiSoft Sandra in "burn-in" mode with only CPU/memory benchmarks selected).

Sounds like success to me! I thought that the hum you were describing was due to electrical noise inside the PSU, perhaps due to over-loading. Turns out it was just airflow noise, I guess. It looks like you won't need a new PSU after all.

I think the VRM's can handle some intense heat. I remember a webpage where the author used a thermal camera to photograph his Epox 8RDA+, and the VRM's were the hottest thing on the board: somewhere around 70C. My VRM2 was going up to 90C under load for a while, until I put a homemade heatsink on it.

It's hard to know whether the 70C CPU2 figure is "safe", though. I run my CPU's at 70C only for brief periods of time. The Tiger MP uses an on-board temperature probe, rather than the processor's on-die probe, so the processors may not really be running "20C under max". But Powergyoza once said that his processors were 100% stable when measured at 84C, using the same motherboard, so 70C sounds doable. Try using Prime95 to load the CPU's, since Prime95 can tell you whether your CPU's are making miscalculations.

The Tiger MP has thermal protection for both CPU's, in case things get out of hand. My MP board has shut down a total of four times over the last two years, usually because I forget to plug a CPU fan in.

These are usually rated to above 100C.