CPU Swaps?

[l008com]

I think I know the answer to this, but it's been a long time so I figured I'd ask in case I'm wrong. 

Totally ignoring aftermarket CPU upgrades, and only referring to original CPU cards...

Are the processors in CPU Macs all interchangeable? Will the automatically work at their correct speed? I know on CPU upgrades way back in the day, you set jumpers to set the Mac's bus speed and CPU speed. Is all that fixed on the OEM CPUs? So if I pulled a 350 MHz CPU out of a 9600, would it work at 350 MHZ if I popped it in my 7300/200?

 

[Elfen]

If this were a 6kK, I can tell you – Yes and No; Yes, they will work; No, not at the original speed. This is because the CPU Clock is external to the CPU. Case in point: The LCIII, there are 2 kinds by apple – the 25MHz and the 33MHz. The only difference between the two is a couple of jumper resistors on the logic board.

Come to think about it, the answer is the same for the PPC – Yes it will work; No, not at the original speed because of the clock speed being on the logic board. Some cards might have their own clocks, but you will then have a fast CPU on a slow Data Bus. You will have to try and see. I remember a few PPC hacks where you can boost the speed of the CPU a slight bit, like: 100MHz to 117MHz on the 5300 series for one; and swapping the CPU Card from a PDQ (266MHz) to a Wallstreet (233MHz) gave you a 266MHz Wallstreet but only because the Data Bus speed was the same on both machines. First verify your Data Bus Speed on the logic board and compare it to the CPU Data Bus Speed on the CPU board, the Data Bus Speed will be your weakest Link.

That is, if the CPU Card fit into the other machine! Make sure things line up properly or else you might have a Smoking Hot Machine – Literally!

 

[Compgeke]

My personal experience has been "Sometimes". Sometimes it works, sometimes it works at reduced speed, sometimes it just sits there with no bong and does nothing. Stuff like the bus speed the CPU card was designed for comes into play, plus multiplier and such.

 

[waynestewart]

If the 350mhz processor is an Apple CPU then it won’t work in the 7300. If it was an aftermarket G3 or G4 then it would.

The 250, 300 and 350 processors in the 8600 and 9600 are not compatible with earlier machines, even earlier 9600. They changed the architecture a bit.

 

[Bunsen]

The 9600 CPU will only work in a 9600 or 8600.

But - every other removable CPU card from a PCI Mac is interchangeable.  The bus speed of the machines in that series are all either 50MHz or 40MHz, and both bus speed and CPU multiplier are set by the card.

If you want confirmation of this, look up instructions on overclocking these machines.  You will see that the resistor mods are all done on the card, not the logic board.

 

[Cory5412]

To answer the original question: no, the CPU from a 9600/350 will fit in but will not run in any other machine, except another Kansas 9600 and a Kansas 8600.

There are two revisions of each the 9600 and the 8600, and the faster ones (I forget the exact cutoff) have a new motherboard and type of CPU and they are referred to as the Kansas machines.

7300 should run an older 9600/233 CPU, however. (There was also an aftermarket /233 upgrade built for 7300, 7500, 7600, 8500, 9500 by Apple.)

 

[l008com]

Hmmm, oh well, good thing I didn't bid. It's actually a 300 mhz what looks like x600 cpu on ebay but guess ill be letting it pass. 

 

[trag]

This covers most of the fine detail:

https://68kmla.org/forums/index.php?/topic/17416-85xx86xx95xx96xx-cpu-cards/&do=findComment&comment=173829

Also, correcting a detail earlier in this thread... The bus speed in PCI PowerMacs is controlled by the CPU card. The clock oscillator and clock buffer chip are on the CPU card and there are several clock lines which leave the CPU card through the CPU slot and carry the bus speed signal to the logic board components. This all changes in the Beige G3 and later, but in the PowerSurge family (x500, x600) and Catalyst (7200 and clones) this is how it works. The CPU card sets the bus speed and the CPU bus multiplier setting is completely local to the CPU card.

Also, as an addendum to the info in the link above, note that there were a few third party 604e card's rated at 250 MHz which were not Mach V/ Kansas/ 604EV and which, therefore do work in non-Kansas machines.