Thanks. I did the MC88920/88916 swap, and pull pin 9 high (?) or something like that.http://homepage.mac.com/schrier/q605_40.html

on one machine but could never get video. But I think my VRAM is too slow. There's a note about sometimes needing 80ns VRAM after the 40 MHz upgrade. I've set it aside for several months though (hmmm, I guess it's been almost two years actually. Sigh).

But I've always wondered why the straight resistor swap won't do the trick. Schrier's page says it doesn't work, but it also doesn't say that anyone ever tried it with the clock generator/buffer swap. It seems to bear more experimentation. One of these days...

Click to expand...

I'd be interested to hear the results.

There's another simpler way to get to 40 MHz which used to be available from here:

http://gabezing.sytes.net/LC475-40Mhz-E.html

However, that site's been unavailable for a while and archive.org doesn't have copies. Does anyone have a copy or know of a mirror? We need to put those up.

The process is simpler than sourcing a MC88916, and simpler installing, too. Just get a 20 MHz oscillator, take the power for it from the 31.3344 MHz oscillator on the corner of the motherboard by the video connector, remove R93 from the backside (also close to the video connector), and run the 20 MHz oscillator's output to the inside pad where R93 used to be (by inside I mean towards the center).

I've done this mod on a number of motherboards, and it's never not worked at 40 MHz.





Here's one of the machines to which I did this modification something around ten years ago:

http://www.mac68k.org/~john/boobookitty/