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Cooling units on Pentium chips

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Raven

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I'm confused as to what systems need and do not need cooling units in the Pentium line - I've seen systems run without them, but I'm not sure if it's intentional or if they just broke or fell off at some point before I got my hands on them.

Specifically, I have a 100Mhz chip in a Socket 5 board and the cooling unit won't stay on, I was wondering if you need it on a system like this?
 
i had a 75Mhz chip that i don't remember having a cooling fan on th heat sync. i think it is probably better to have a fan there and not need it rather than need it and not have it.
 
Does one definitely need a heatsink, then? When I say "cooling unit" I meant the whole heatsink and/or fan combo - this box has none at the moment but it's just been stored for a few months, so hasn't been operating since it lost it.
 
I think they pretty much all need them (and some should even have it written on the top like AMD does). Some OEMs didnt use a fan but had some super large heatsinks and maybe a case fan blowing over it (like the early Packard Bell P66 machines). There could be special embedded versions that got away with small heatsinks and no fans (I have a TI 486/100 that didnt have anything on the chip and it was meant for industrial designs).
 
I've got a P5 goldtop (60MHz) which has no heat sink but a small fan which I added when it overheated.

I also have an Intel Pentium 133MHz which came with a fairly large heat sink and attached fan. I unplugged the fan and it still works like a charm on hot 35° C (95° F) days. It is an open frame so there is no case fan. It has been on 24/7 for a couple of years now.
 
I've always liked HP's way of handling P1/P2/P3 cooling--use a heatsink, but leave off the fan--instead use a duct from the main (large) case/PSU fan to direct air over the heatsink. The headsink fins don't plug up with dust and the machine is deathly silent.
 
It's just not easy to apply that theory to any given case, which is unfortunate - you have to find a computer with that sort of system in place.
 
Another trick I've used to get Pentium machines to run fanless is to use a P3 or Athlon XP heatsink and remove the fan. They're designed for a much higher thermal load, and usually stay close to room temperature unless your case just has no air movement. Copper-core aluminum Athlon XP heatsinks (the generic ones that came with the XPs and were more or less completely insufficient) do a really nice job.

EDIT: and if you're having trouble with heatsink clamps, grab some Arctic Silver thermal /adhesive/. Use four dots (sparingly!) on the corners of the processor and fill the space in between with regular thermal paste, and you'll be able to separate the heatsink from the processor if you need to. You can use the adhesive across the whole processor, just like regular thermal paste, but you seriously risk damaging the processor if you ever need to pop the heatsink off. Also, thermal tape or "frag tape" works, but not as nice of a finish.
 
glitch said:
EDIT: and if you're having trouble with heatsink clamps, grab some Arctic Silver thermal /adhesive/. Use four dots (sparingly!) on the corners of the processor and fill the space in between with regular thermal paste, and you'll be able to separate the heatsink from the processor if you need to. You can use the adhesive across the whole processor, just like regular thermal paste, but you seriously risk damaging the processor if you ever need to pop the heatsink off. Also, thermal tape or "frag tape" works, but not as nice of a finish.
Click to expand...

Call me old-fashioned, but I use good old Permatex anti-seize compound (the silver kind). There are several tests using this showing that it's no worse than most silver pastes--and it's non-conductive. To hold a heatsink onto the ZIF socket, I simply fashion a clip out of a 15 ga. stainless steel bicycle spoke.
 
Chuck(G) said:
Call me old-fashioned, but I use good old Permatex anti-seize compound (the silver kind). There are several tests using this showing that it's no worse than most silver pastes--and it's non-conductive. To hold a heatsink onto the ZIF socket, I simply fashion a clip out of a 15 ga. stainless steel bicycle spoke.
Click to expand...

Indeed, I use white beryllium oxide thermal paste on most of the "higher performance" stuff I play with (large MOSFETs and such), simply because we get it in gallon cans at work. Apparently contact with the eye causes you to go blind in a horrible, painful way though. We also use it on heatsinks with computer processors at work, and it seems to perform as well as Arctic Silver 5 (hardware monitors report around the same temps...we've not actually done tests on the two).

I do like Arctic Silver's thermal adhesive though, for cases where you can't really attach a heatsink with clamps -- the best example of that being an overheating PC/104 board I've got, which uses one of those 486-compatible System-On-Chip modules. I'm pretty sure its original enclosure involved part of the chassis contacting the top of the SoC for heatsinking, but there's nowhere to bolt a heatsink to. So, I stuck an old southbridge heatsink to the top!
 
Cheap radioshack heatsink compound is what I use (and very little of it). Quite a few Pentium1-3 heatsink/fans use a thermal strip so you don't need any heatsink compound. Luckily I snagged a dozen or more new P1 and P3 heatsink/fan combos a few years back when they were dumped so I have stock (wish I did the same for 486's).

The P60/66 were 5V and ran very hot, if the fan that pulled cold air over the large heatsinks (glued onto the chip most of the time) failed so did the CPU.
 
For P1s I usually use passive cooling unless I'm overclocking. A 486 aluminum heatsink will usually fit a Pentium, and the wire clippy will usually work, too. If I'm overclocking I put on a fan, or if the original system included a heatsink/fan combo then I'll use that. One of my 166s has a fan, the other doesn't.

Monitor your temps, run a demanding program. Add a fan if necessary.
 
saundby said:
For P1s I usually use passive cooling unless I'm overclocking. A 486 aluminum heatsink will usually fit a Pentium, and the wire clippy will usually work, too. If I'm overclocking I put on a fan, or if the original system included a heatsink/fan combo then I'll use that. One of my 166s has a fan, the other doesn't.

Monitor your temps, run a demanding program. Add a fan if necessary.
Click to expand...

I wasn't sure if a 166 would be OK w/o a fan. That's good to know.

I think you hit the nail on the head when you mention load. People are obviously going to have different ideas of what is "normal". I would never in a million years run a game so that wouldn't enter my mind, whereas a gamer would take it for granted and create a lot of CPU load.

Is there a way to measure temperature without some sort of special, and probably expensive, probe placed under the CPU?
 
Ole Juul said:
Is there a way to measure temperature without some sort of special, and probably expensive, probe placed under the CPU?
Click to expand...

Many DMMs come with at least the capability to read type K thermocouples and many come with one. In any case a type K bead-style 'couple will run less than $10.
 
Chuck(G) said:
Many DMMs come with at least the capability to read type K thermocouples and many come with one. In any case a type K bead-style 'couple will run less than $10.
Click to expand...
Gotcha. I was thinking one would have to use a special solid riser or something, but of courser there's a little space underneath. I wonder how close that reading would be to what the chip manufacturer quotes. Does the 'couple need to be glued or pushed against the CPU and at what place does one get a legitimate reading?
 
from Chapter 10 of the Pentium Development Manual

10.1. MEASURING THERMAL VALUES
To verify that the proper TC (case temperature) is maintained, it should be measured at the
center of the package top surface (opposite of the pins). The measurement is made in the same
way with or without a heat sink attached. When a heat sink is attached, a hole (smaller than
0.150” diameter) should be drilled through the heat sink to allow probing the center of the
package. See Figure 10-1 for an illustration of how to measure TC.
To minimize the measurement errors, it is recommended to use the following approach:
· Use 36-gauge or finer diameter K, T, or J type thermocouples. Intel’s laboratory testing
was done using a thermocouple made by Omega (part number: 5TC-TTK-36-36).
· Attach the thermocouple bead or junction to the center of the package top surface using
high thermal conductivity cements. The laboratory testing was done by using Omega
Bond (part number: OB-101).
· The thermocouple should be attached at a 90-degrees angle as shown in Figure 10-1.
· The hole size should be smaller than 0.150” in diameter.
Click to expand...

as passive heat-sinks were the norm then.. the probe was vertical to the chip face.
Now active heat-sinks are the norm to test processors they make a groove in the chip heat-spreader to fit the thermocouple
 
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For socket 4 motherboards (pentium 60/66), I figured out the cooling solution that best fits and is actually available. (try finding a socket 4 heatsink fan, you won't).

That is, a pentium pro heatsink/fan. I had my poor little socket4 board for ages, but couldn't really use it due to lack of cooling, but one day I got a dual ppro and sized it up, prefect fit. So I bought a cheap atx board that came with a ppro200 just for the heatsink. The width is perfect, I just had to bend back the "long" side of the clip arms. Fit the socket clips perfectly and clamps well to the cpu. Bonus is the ppro heatsink is nice and large.
 
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