Mac OS 9 Lives
Mac OS 9 Discussion => Hardware => Topic started by: mcmcjohn on September 22, 2025, 02:32:32 AM
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Hello. The model I have is the Power Mac G4 Gigabit Ethernet. Originally, it had a single-core 1.33GHz CPU, but I wanted to upgrade to a dual CPU. So, I bought a DP 1.0GHz module from a Quicksilver, and I heard that by changing the resistor values, it could be overclocked to 1.2GHz or 1.33GHz. I moved the resistors accordingly to make it 1.33GHz. I also completed the additional 12V power supply modification.
However, after booting, both Mac OS 9 and Mac OS X still recognize it as 1.0GHz. Since this model only has a 100MHz bus, is it normal that changing the resistor like this doesn’t make it show up as 1.33GHz?
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All that the resistors can do is to change the multiplier which the CPU is told to use to configure its internal PLL (clock generator). The OS that is running doesn't "recognize" the CPU speed: software can either perform a CPU benchmark to measure processor performance, or else identify the model and revision of the processor to display the expected clock frequency. In most cases it's the latter, which means that overclocking will not change the displayed frequency.
A program like Newer Technology's Clockometer will try to measure the frequency by testing how many steps of the Decrementer register changes during a second (which comes from the real-time clock, not affected by the processor's clock). It should have a linear relationship to the real CPU speed, but there is some error. Since Apple doesn't want to receive complaints that their 1.0 GHz computer only reports "997 MHz", they don't use this type of measurement in System Profiler.
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OR... you might even try:
https://macintoshgarden.org/apps/machspeed-control-combo
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Chances are you should believe what you see in "About this mac". Apple does fudge the numbers (silly things like reporting a 666.66mhz as 667 so as to avoid being devilish), but you should see SOME difference, if changing the resistors did anything.
But DO give Clockometer (or something like that) a try, it doesn't lie. If it is still reporting 1.0 ghz, then that is what your system is running at. (Although the one I use is a MacOS 9 program, not sure if there is an X version).
This is strange, since what you did sounds like it should have worked.
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OR... you might even try:
https://macintoshgarden.org/apps/machspeed-control-combo
I always preferred this one:
(https://macintoshgarden.org/sites/macintoshgarden.org/files/screenshots/PB_1400_Gauge_Pro.jpg)
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Thank you, everyone. I tried running the Machspeed control on both OS 9 and OS X. On OS 9, it was recognized as 996MHz, but on OS X, it said the processor wasn’t supported and asked me to email the processor code to the company. I also checked with Clockometer, but it was likewise detected as an unsupported CPU, so I’m thinking of giving up for now… I guess I’ll just settle for 1GHz.
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FYI I have a 1 point something dual processor upgrade in my G4. About Mac and/or System Profiler reports it as a "60?" (should be "74xx" for whatever kind of G4's they are). I haven't tried machspeed-combo-control on it, but would not be surprised if I see what you are seeing, ie the cpu may be newer than the software.
I would trust clockometer in MacOS 9. I have various other cpu upgrades for other machines, and it always seems to report what the machine REALLY is running.
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FYI I have a 1 point something dual processor upgrade in my G4. About Mac and/or System Profiler reports it as a "60?" (should be "74xx" for whatever kind of G4's they are). I haven't tried machspeed-combo-control on it, but would not be surprised if I see what you are seeing, ie the cpu may be newer than the software.
I would trust clockometer in MacOS 9. I have various other cpu upgrades for other machines, and it always seems to report what the machine REALLY is running.
My CPU is actually a DP 1GHz unit extracted from a Quicksilver model, so it can’t really be considered a Newer CPU, but I don’t know what the cause is. In fact, even before mentioning that, my Power Mac G4 doesn’t show a serial number in System Profiler—the serial number field is blank. And according to a site that covers CPU modifications, installing a DA or QS CPU into a 100MHz bus machine often fails, so it’s not something to expect much from. That’s why I think I might just be satisfied with the fact that it runs at 1GHz at all.
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Oh, just to clarify when I said "newer" I meant with a lowercase n, and not Newer as in the company.
As in the CPU itself came out after the MachSpeed app was created, so it doesn't have information about it. (This is the reason, in Tiger at least, my G4 shows up as a "60?").
Hmm...the bus speeds. So if the CPU card was designed for a faster bus, things get confusing. You'd think it'd be fine because in effect, you might be underclocking the cpu, but at the same time it wasn't designed for it, so its no wonder there can be problems.
The resistors can only modify multipliers of the bus speed the motherboard is providing on the cpu connector, so in your case things are an odd case. I guess I'm not surprised things are "looking weird", but it all sounds like it SHOULD work, but I might be missing something.
The cpu's themselves may be confused, and not allowing a particular (faster) speed?
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there are machines/boards where the bus/processor ratio may not exceed 1:10, but i dont think that is the case for blue G4s / DA gigabit.