During the past two-three weeks I've been rebuilding my computers in hope that I can achieve a quiter overall operation. Prior to the overhaul I had two computers, my main rig with four harddrives and a backup 24/7 rig. After overhaul I ended up with three computers: fileserver, which now stands in the closet, my main rig and the 24/7 rig. The problem with that was that in the end (when my fileserver was shut down) my main rig turned out to be so quiet, that I had touble differentiating between the noise it made and the one 24/7 rig was making in the closet. So even though I did not anticipate to overhaul 24/7 rig, now I had to.
I already made a thread about a fileserver rig. So this is the second in the series which describes the new and updated 24/7 rig.
Quick specs
Athlon XP-M 2500+ (35W) with AeroCool HT-101
Shuttle AN35N/ULTRA
512MB
Matrox G450 16MB
3COM 905C-TX
Seagate 7200.8 400GB IDE
Power Brick PSU and a couple of undervolted panaflos
A bit of history
Originally I built this rig to be completely silent. Well, as you are aware already, that didn't work quite as well as I expected. Well, in the beginning it was silent, that is until I got used to the new noise floor, so now it's getting on my nerves again.
Originally I didn't want to buy another case so used one I already had - an aluminum Kingwin. The case actually has very decent airflow, even if it lets a lot of noise out of the front. Of course being an aluminum case it's very prone to vibration so I applied lots of dynamat to the side panels and to the top. The difference was amazing (although most of SPCR'ers already know that). Knockin on the side panel produced a dull sound, much much better than a regular steel case. The case was still prone to vibrations, but the amplitude of vibrations was smaller than with regular steel case. Subjectively, overall vibration induced noise was on about the same level as steel case, maybe a little better. The case does have soft rubber gourmets which are used to silence the hard drive. These are the best gourmets I have seen after P180/150 gourmets, they are much much softer than the ones used in SLK3000. They were doing a good job, but not good enough for me so I suspended the drives using elastic strings (see the first article). Originally I built this rig more than a year ago, at which time I felt that underclocked/undervolted Mobile Athlon XP with 35W power rating was the best way to go. The CPU actually seems to be a good one. I haven't done any stress testing, but it is completely stable under normal usage at 1064MHz at 1.1V. Like many if not all Mobile Athlons it cannot start at 1.1V, so I have set the voltage to 1.25V in bios and drop the core votage in windows using 8rdavcore. Of course there are better CPU options now, but at that time that was the best low heat and relatively inexpensive CPU. The motherboard is Shuttle AN35N which doesn't have onboard video or Gigabit Lan or SATA ports (unlike my fileserver), but for its purpose it's doing fine.
The box is all positive pressure with two undervoted panaflo's softmounted at the front intake. For the CPU cooler I chose AeroCool HT-101 which is an excellent cooler when a fan forces airflow over it, my dad has AXP3200 and HT-101 manages to keep it at 32 degrees idle with 2000RPM 80mm fan (my dad has a very different noise perception than I do). Anyway, the idea was that the two panaflo's at the front will cool the harddrive and force enough air through through the case to cool CPU heatsink as well. Well, the harddrive did stay very cool, unfortunately HT-101 wasn't very well suited for such semi-passive operation and the CPU idled at 45 degrees celsius (keep in mind that was while it was underclocked/undervolted down to 1064MHz/1.1V). Not a very good result. In the summer I had to slighly raise the voltage for intake fans to keep the CPU at 45 degrees.
The PSU is a 120W brick type PSU. The brick power supply is very much like the one recently reviewd by SPCR but it's made by FSP Group, and the fan always stays on. Although on a bright side it's fairly quiet, about the same level as average HDD or about 22-24Db, and tacked as far back in the closet as humanly possible it's nearly if not completely inaudible over the idle noise from hard drive.
Why change?
Well... I wouldn't mind slighly higher than normal CPU temperature and somewhat sluggish performance resulting from underclocking CPU, but the main reason for change was that after a year I have finally got used to the new noise floor and that the box was getting a little too loud for me, especially since my main rig had finally become as quiet as this one, if not quieter in some aspects (mainly HDD noise).
The noise sources from the box now were idle whoosh from the hard drive, air whoosh from fans that weren't spinning at their minimum RPMs and case vibrations since there was very little room to suspend HDD and it was making partial contact with the case.
With the new modifications I have tried to address all of these problems.
Exhaust duct
One of the mods I did was build a little exhaust duct. The main purpose is to muffle the sound and direct it away from me at the wall. It worked fairly well. There was definite improvement in the fan noise, however there was very little noise improvement in the HDD idle whoosh.
CPU heatsink and CPU duct
The next mod was to softmount a low speed panaflo fan under heatsink. Since this is an aluminum case which tends to vibrate even when damped with dynamat, the softmount was absolutely necessary. The fan is of course undervolted to reduce RPMs even more. The duct was used to direct the hot air towards the rear panel.
Mounting a fan on CPU heatsink also allowed me to slow down two intake panaflo's to the minimum (which previously were used to cool CPU as well) so that was another side benefit.
When I turned on the computer I set the multiplier at 14x (133MHz FSB) and the CPU voltage at 1.35V since I figured the heatsink should work very well with the fan underneath it now. I watched the temperature in 8rdavcore and it kept rising. When it reached 37 degrees I thought the fan underneath the CPU did not start so I opened the case, but no - it was working. The temperature kept rising until it was 40-41 degrees at idle, although the heatsink was barely warm. I must say I'm slightly disappointed in Mobile Athlon. Sure, HT-101 is not an ideal heatsink for low aiflow operation but Zalman 7000 in my fileserver isn't either. And yet my mobile celeron idles at a lower temperature with only a very loose duct on it. Of course I must take into an account that Mobile A-XP is going to be much more powerful than Movile Celeron at identical frequencies, but this begs the question about processor power ratings. Both CPUs are rated 35W, however it was universally assumed that when intel rates their CPUs they measure power draw at 70% or so load, and when AMD measures, they measure it at full load. So you'd think Mobile A-XP would run cooler, and yet my test results indicate different. Yes, you could point out that the two processors had different cooling systems, but personally I feel that HT-101 with an undervolted fan underneath it should have provided a better cooling than very losely ducted Zalman 7000. Who knows, maybe I'm fundamentally wrong somewhere, but I still feel disappointed with power efficiency of my Mobile 2500.
HDD
As I have already said there isn't a whole lot of room to suspend the hard drive in the case so the drive was making partial contact with the case. Since there was only one hard drive I wanted to mount it vertically, but as I opened a case I noticed there was a horizontal divider in the drive bay. D-oh! I completely forgot about it. I didn't want to cut it out, and fortunately the height of the lower chamber was just enough to fit the drive in. So what I did I screwed wood mending metal plates from ACE hardware to the drive so it wouldn't fall over and put two pieces of thin motherboard foam both underneath and above the drive. It was a tight squeeze and I was afraid that the vibrations are still going to be transmitted to the case, but in the end it worked out much better than previous configuration. The case vibrations are now almost gone, I can still feel them if I put my hand on case and really concentrate on it, but they are very very minimal. Hard Drive seeks, especially long range ones across the whole platter, are more noticable, but they are muted as well. Overall, if it wasn't for the long seeks, I'd say it is almost as good as completely decoupling the drive.
Unfortunately the idle noise was still present so I also mounted a think piece of foam on the right side of the case and a thinner one on the left (an idea I took from building my main rig of which I will elaborate more in the appropriate thread). The idle noise was cut down very drastically considering such simplistic mod.
The hard drive temperature with the new configuration stayed the same - 34 degrees celsius which is perfectly fine end expected for a three platter Seagate.
Power Supply
As I have said before the power supply is a brick type PSU which consists of a power adapter and a power board. It's rated 120W total. The power supply is made by FSP group. The fan is always turned on, but it's nowhere near 36DB like the one SPCR reviewed. I noticed something funny about it though. It was never loud, actually very quiet, quiet enough for me not to be noticable when sitting behind the wall. However for some reason after I've done my modifications it got louder. Something that I've changed must have made it spin faster. I don't know if it was increased CPU frequency or additional fan, but it got loud enough for me to hear it at night. At first I thought it would go away, it didn't, I tucked it even further into the closet, but it was still audible. It got so annoying that it almost convinced me to buy a fanless 80W model. I actually started shopping but as it turned out all of the newer power bricks output 12V, whereas my version works only with 14-19V. Ooops. I searched for the appropriate power adapter and couldn't find anything. Desperate and not knowing what to do I considered buying another brick PSU or even antec phantom, but then I remembered that I had a spare 90W Kensington universal laptop power adapter. Yay... Not so fast. I picked an adapter that provides 15V output, guess what? The physical dimensions are different so it doesn't fit the jack. OK... I manually check all connectors and only 3 out of 12 or so fit. Next step was a timeconsuming one. The manual for Kensington adapter lists compability with laptops, but it doesn't say which connectors provide which voltage and which pin is the positive one. And I was off to google. Took me about 30 minutes, but I finally found connector that provides 19V with center pin positive. Just as a precaution I disconnected hard drive in case anything goes wrong, but it didn't. It worked almost flawlessly. With everything connected the votages within 2%. Very nice. The adapter does get hottish now that the ambient temperatures stay at 28C. I suppose it's natural given that it's usually really warm even at 21-22C ambient. I tried putting it right in front of the case air intakes but it didn't really help. I hope it doesn't die on me and if it does it doesn't take anything with itself. Now I'd like to say the power adapter is silent, but it's not, it has a very quiet coil whine
Fortunately I can't hear it at all behind the wall.
Old FSP fanned power brick
New Kensington fanless power brick
Overall
Overall, despite adding an additional fan to the system to cool CPU the noise went down. I attribute it to the new HDD soft mount as well as damping it with foam and lowering speed of intake panaflos. The CPU also idles at the same or lower temperature now even when working at full frequency which is another benefit - computer feels much snappier. The HDD is still audible if I put my ear at the side of the case, but it's OK because the computer sits in the closet. Deep at the night with no ambient noise whatsoever I can still hear the computer, mainly the hard drive, but the noise is very very faint, barely audible. So for now I'm satisfied with the new mods I have made, that is until I get used to the new noise floor and the cycle repeats again...
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