Here is what I did:
Go get Intels specifications on this processor at ftp://download.intel.com/design/archive ... 318504.pdf
and read section 5. Maximum operating temperature is 70C (158F). Nominal power disipation is 7.9W, maximum is 17W. Use the equations on p46 and the table on p48, not p50. Measure my highest heatsink as ~1". Estimate my Laminar Air Flow in linear feet per minute based on dividing my estimated CFM through the case by the cross section of the smaller of the intake and exhaust. Estimate ambient temperature around the CPU at ~30C (86F).
From all the calculations I determined that at least it was worth trying to run without a fan. I also learned that trying to base laminar air flow estimates on input/output cfm is very difficult. There is now way I am getting over 5000 linear ft/min at the CPU. Their table only goes up to 800. The cross section of flow at the CPU is way bigger than the cross sections at the input or output, unless you add ducting. Calculating the effects of the cables and other obstructions is hard to do accurately. Intel also assumed a certain heatsink geometry. There's sounds like its composed of needles, mine is composed of fins.
So, now for the fun
I openned the case, pulled the wire for the CPU fan (still on the heatsink hampering flow mind you). I left my finger on the heatsink figuing I could likely take about 115F (46C) before it hurt too much. It booted fine! After a few minutes though, it hurt too much
. So, downstairs I went to grab a meat thermometer from the kitchen
. It fit neatly between the fins of the heatsink. It got up to about 130F (55C) with the case open and the computer playing internet radio. Good!
Next I closed the case for 15 minutes. When I openned it the temperature was only 120F (49C)!! Why? Because the closed case reduced the effective cross section to flow at the CPU, or so I figure. But internet radio is not stressing the processor. Whats the solution? Download Prime95 and run the stress test!
With the case open the temperature made it up to 146F (63C). The nice thing about Prime95 is that it makes the processor hot and gives an indication if the processor starts making mistakes because of the heat.
Its been running for 2.5 hours without failure with the case closed!!
Over the weekend I will make a few more improvements for a bit more margin:
remove the fan from the heatsink, install round floppy and IDE cables, and try a bigger SocketA heatsink. Here is the heatsink http://shop.store.yahoo.com/svcompucycle/svcgc21.html
Tom, you were right, kind of. I now know what the next highest source of noise in the room is. Its no longer my wifes computer, its mine
! I now have a Zalman fan controller coming to turn down the noisy fan in the Thermaltake Golden Orb on my 800MHz SlotA Thunderbird.
I hope this benefits others,