Subject: Overclocking Quadra 605s and Performa 475s
To: Kris Jones <>
From: John Klos <>
List: port-mac68k
Date: 05/31/2002 15:19:30

Here is a quick HOW-TO on overclocking Quadra 605s and Performa 475s. I've
successfully overclocked nine of these to 40 MHz, and all are stable and

Most of the information is already available from:

That site isn't exactly very clear on certain things; so, to simplify,
here is what you need to do:

1) Perform the resistor swap as indicated to bring the system to 33 MHz
(this decouples some other clock, I guess; the system won't be stable at
40 MHz without doing this)

2) Get a 20 MHz oscillator and connect pin 7 (or the equivalent) to pin 7
of the 31.33 MHz oscillator on the rear right corner of the motherboard;
also connect pin 14 to pin 14. These are ground and +5 volts, respectively

(20 MHz oscillators can be bought from, say, Digikey(.com))

3) Remove R93 from the back of the motherboard. Then run a short wire from
pin 8 of the oscillator to the R93 pad that is closer to the middle of the

That's it! I know this is basically what that web page says, but I hope my
language is a little clearer.

Finally, of course, if you want to run NetBSD now, you'll need a real
68040, not an LC040. We're still working on creating a binary snapshot of
a NetBSD system that does all floating point via software.

Then go buy a 64 meg SIMM for $12 USD and you'll have a very happy Quadra

John Klos
Sixgirls Computing Labs