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PPCMLA Press Corps

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Shades of CHRP

I recently found an IBM 333MHz 604e ZIF module on eBay.  I don’t know for sure what machine it comes out of, but it’s most likely an RS/6000 of some sort such as the IBM RS/6000 43p Model 140. I had a hunch that IBM capitalized on their R&D for CHRP hardware by rolling the ZIF module design originally intended for Mac OS clones into their pSeries machines when CHRP died a slow and lingering death.  And if that hunch is correct, then these processor cards should work in a ZIF-based Mac like the beige G3.

IBM PPC 604e vs XLR8 Motorola PPC 750IBM PPC 604e vs XLR8 IBM PPC 750: Back
The 333MHz 604e and a G3 ZIF compare favorably.  They are the same size and have the same pin count.  The 604e is slightly taller than the G3, but only maybe by 1 or 2mm or so. So I set about fitting the 604e into a desktop Beige G3 I had lying around doing nothing.

My first observation is that the fit is a little tight. The module didn’t drop into the socket effortlessly as one would expect with a Zero Insertion Force module. That might be because some of the pins weren’t perfectly straight. This is a 2nd hand processor module, after all. The second observation is that fitting the G3 heatsink over the taller 604e is a little difficult. It will fit, but it takes an unsettling amount of force to secure the heatsink clip to both sides of the ZIF socket.


Knowing that the module is indicated as a 333MHz part, I set the motherboard jumpers for 6x (set jumpers 2, 5, 6, and 7 for a 6x CPU multiplier, a 66MHz bus, and 33.3 MHz PCI slots). Of course, I don’t know whether or not this particular 604e will support a 6x multiplier, but it seems like a pretty safe bet that it does. And what do you know, the Mac chimes!

It booted all the way to the desktop. I ran Apple System Profiler, NewerTech Gauge Pro, and MacBench 5 to show me info about the CPU module. All three recognize it as a PowerPC 604e. Interestingly, Apple System Profiler and Gauge Pro both say it’s a 333MHz part, but MacBench 5 recognizes it only as 166MHz (half the expected clock speed). I ran integer and FPU tests in MacBench 5 to rate the CPU relative to a stock 300MHz Beige G3. The results were surprising. The integer test turned in a dismal 525 which is roughly half what I would have expected. The FPU test turned in 1104 which beat the stock G3 by a hair. So the MacBench scores bear out the notion that the CPU really is only running at 166MHz. Hmm. Does anyone know why that might be or how to get the module to run at the full 333MHz?


Incidentally, the heatsink got pretty hot while the system was booted. I didn’t have a thermistor, but it was definitely hot to the touch and considerably hotter than the G3 every gets.

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