Downclocking PM8100/100 or 110

[ojfd]

Calling all experts...

Has anyone of you ever done this or have any inside info on how to do it?

What I would like to do to the above mentioned machines is:

1. Install 40 MHz oscillator to make all subsystems and RAM run @ 40 MHz.

2. Downclock PPC601 processor back to 80 MHz since I don't want to overcook it. I will be running NewerTech G3 PDS, so all I need is 40 MHz bus.

Cheers,

OJ

 

[johnklos]

Hmmm... That's not going to be easy unless you have an 8100/80 to look at. The multiplier on the 100 and 110 MHz machines is three, so if you change the oscillator to 40 MHz, the CPU will run at 120 MHz unless you can change the multiplier to 2.

On the other hand, when you install the NewerTech, the 601 should idle, so the speed shouldn't be a big factor.

 

[Byrd]

There is no point to downclocking the CPU - the G3 upgrade is independant of the existing CPU itself (that is, it is not used), nor are you going to "cook" the existing 601 CPU (it hardly runs hot anyway!). The Newertech upgrade should also let you set the multiplier and/or bus speed to a rate you are comfortable with, such as 35 or 40Mhz - it also control the bus speed independant of the clock generator on the motherboard itself.

JB

 

[Floydy]

There is no point to downclocking the CPU - the G3 upgrade is independant of the existing CPU itself (that is, it is not used), nor are you going to "cook" the existing 601 CPU (it hardly runs hot anyway!)

The existing CPU is only used to boot the computer to a point where the G3 CPU/extension kicks in...

 

[Bunsen]

The big advantage of a 40MHz bus, so I hear, is that it puts it into lockstep with the 10MHz Nubus. This has been alleged elsewhere to improve Nubus performance.