I've read quite a few reports about the heat shield and thermal paste for the 900MHz G3 upgrade. I understand that the new processor adds thickness to the daughter card so that the original heat sink/pipe can't be attached to the daughter card.

As a result, the old heat sink/pipe that channels heat away from the processor and RAM isn't used. The Powerlogix work-around is to just add a copper heat shield and thermal paste, but isn't there some way to create a modified heat sink/pipe that will channel heat away from the processor? Plenty of people who have purchased upgrades that I've e-mailed say that the upgrades work fine, but some are concerned about leaving all that heat next to the processor and the RAM. Likewise, that's a concern of mine that's keeping me from purchasing the upgrade right now.

Has anyone (Bradley) tried to modify the heatshield so that it works more like the original processor/daughtercard? I use a cooling/fan base with my 500MHz Pismo, so I'm sure that will help reduce heat, but I'm paranoid about cooking my expensive new processor upgrade.

Actually, the original heat pipe DOES fit above the 900 CPU, and if the grey insulation material is removed, the heat shield screws down tightly over the CPU (leaving a good impression of full contact from compound), with a slight centered bulge. The keyboard then latches over with a slightly less pronounced bulge around the "ERTY" keys, not enough to be a problem closing the lid or pressing against LCD (no more than how lower keyboard keys contact LCD normally).

If compound was used between the heat pipe and heat shield, there would be both the heat pipe moving heat and also the heat shield as PL modified, so there should be good heat drawn off. Want to be the first to test out the idea!?

My 900 CPU runs ultra cool (105º F normal use) by using both a PCMCIA card cooler fan and a USB 3 fan cooler base, so there's no motivation for me to experiment further.

I also used Artic Silver's Cermanique compound, and my running temps have actually dropped even lower after the compound has set. It's 100% non-conductive and one of the highest rated compounds available.

Could you test what your CPU temp is with just the USB 3-fan cooler base and the Artic Silver compound?

I already have a USB-powered 3-fan cooling base, but I haven't been able to find a PCMCIA card fan here in the states from a reliable online store. I'd also like to keep my PCMCIA card slot open for USB 2.0, Firewire, and memory card adapters.

I'd like to keep my CPU temps in the 100-125 range without resorting to a PCMCIA card fan.

Turning off the PCMCIA cooler fan (but with USB cooler base running) climbs temps quickly to around 125º F for low CPU use (such as web surfing for hours) and +135º F for high CPU use such as running EarthBrowser or MacAquarium (85 - 100% CPU non-stop).

125º F is very manageable, with heat only noticeable near the Power button and LCD hinges. Going to +135º F and the rest starts to get warm. Continued long term, high CPU use can only be expected to get quite hot eventually without agressive cooling.

The USB cooler base (I use the CyberCool 3 fan USB widely available on eBay for $18 with shipping) really helps, but the PCMCIA fan is just awesome for Pismos, with the air directly blowing at the CPU (as long as Airport card is NOT installed).

Also, the Kengsington USB Flyfan (CompUSA $10) really works, if noisy and short-lived with constant on running.

Be SURE NOT to use Artic Silver 3 compound, as it IS conductive enough to be a real problem with the 900 CPU having caps very close to the CPU's face. A conductive contact resulting in a short could destroy the CPU instantly. ONLY use 100% NON-conductive compounds if you substitute what is supplied with the 900 upgrade kit. Cermanique is the version AS made compound I highly recommend.

Also, clean both face mating surfaces with isoprop alchohol (not rubbing) and cover finger with saran wrap applying compound so no lint or especially fingerprints contaminate the joining process. Cover both mating spots with the LEAST amount of compound to just fully cover each surface when spread out hard with finger pressure. More is NOT better when it come to compound, only enough to "wet" the contact area (which is only less than 5x7mm tiny).

My temp readings are being measured by modifying a PC computer LCD bezel kit sold by CompUSA for $20 (sku #294976). It is two self-powered temp sensor/LCD ºF readouts that can be popped out of the bezel and become very small remote temp sensors. The cable can be feed through the vent by the fan and sensor taped on top of the heat shield to give feedback readings. Figure actual CPU running temp to be maybe 20º F higher than heat shield temps I've mentioned.

My regards guys...excellent posts with some great information.

-Bradley
POWERBOOKMEDIC.COM