Thursday 31 December 2009

Computer Build #2

Ok, it is 4am and I am running strong on about 7 espressos... I wish I was more inclined to do real work or sleep right now, in limbo... onto the post.

Cooling:

I decided (prompted by wanting the most cooling at the least dB) to ditch the 92mm fan and replace it with the silent Akasa 120mm fan... should be a zip-tie bodge job, which is actually my middle name - Michael zip-tie-bodge-job Barkley; operational but at risk. Anyway I could just be blowing warm air (ha) because I haven't seen the board and I can't say what will fit, but that is the plan.

Additionally I have 2x120mm Arctic Cooling case fans (1 for a top blow-hole type use) and the other for hopefully routing the hot CPU air out to the back. Pretty cool (pun after pun... almost tiresome to write) that the blade design on the Akasa 120mm fan in the previous post offers a 5dB reduction in volume with a 23CFM increase in air flow... all blade design and layout. Awesome stuff - they both run at about the same 1,400RPM or so (between 800 and 1,500 I think are the operational limits).
120mm, 22dB(A), 37CFM

Providing the main hurricane is an 180mm Akasa fan which should deliver 51CFM (not the most CFM, but quiet and actually plenty of air).

180mm, 15dB(A), 51CFM

This I plan to mount on the side of the case and have air blowing directly onto the northbridge, RAM and CPU. Not totally traditional cooling, but I think for my purposes it will be good. Worst case scenario is that I move some fans - no big deal.

I am aiming for a slightly positive pressure system to keep dust intake through air leaks to a minimum, but with huge fans I will be planning on a fine mesh, like a fly screen - mainly to keep out hairs and large debris - fine mesh could end up murdering the air flow. Some use tights... pity mine are all laddered.

Cutting an 18CM circle to give clearance for that large fan will be a bother since I have no hole saws that large (nor should I!), so I will drill a series of 3-4mm holes along the circumference, get that roughly cut out, then with a small grinder bit (in the drill, a cylinder) I will smooth it, finish with sandpaper, and in all likeliness it will look like something from SAW. I am going to check out some plumbing fittings, there could be some convenient sizes which would cover up the roughness.

I will be mounting the fans with a layer of foam (from a Tesco camping mat - waaay cheaper than sticky foam tape) between the case and the fan - less vibration noise I hope! Double sided carpet tape to the rescue; it is VERY sticky!

Finally, and I will confirm this at a later date, but some modern PSUs suck air INTO the case. Maybe to increase circulation within. To me it seems stupid - they are at the top and at the back, a prime area to suck air OUT I would have thought. So, they distribute pre-warmed air in the system; not on my watch. 2 options:

1) Turn the PSU upside down and cut a hole in the roof of the case.
Pros: PSU has good cool air 100% of the time.
Cons: A pain to cut another hole.
2) Take the PSU, open it and flip the fan around, thus making it suck.
Pros: Should be easy, no case hole, more air throughput in the case.
Cons: Warm air through PSU, could lead to a negative pressure system.

I will have to see how the connections are organised on the unit before I start destroying everything! I wish I had huge hole saws. Or a good bandsaw (unrelated, but it would make guitar building much quicker.)

My last 2 days have involved:

Thinking (overclocking, BIOS, cooling, fans, voltages, life, existence, motivation, objective)
Forza 3
Trumpet
Coffee
Sleepwalking
Cacti

It is cold, my bed is warm, best leave now! Parts arrive tomorrow (today in a few hours I hope to be realistic since 5am is on the way up).

Mike

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