constructing TTL frequency divide by x question.

From: jpero_at_sympatico.ca <(jpero_at_sympatico.ca)>
Date: Wed Mar 28 15:52:26 2001

Hi all,

Doesn't make sense to buy single TTL oscillator while I have
lots of other osc chips that has compatiable frequencies that I can
divide down.

A computer needs 12.5 MHz TTL oscillator to clock that '040 at 25MHz.
Right now that motherboard uses 10MHz OSC nearby for a bogus 'LC040
20MHz and have a real '040-25 coming in to swap out that fpu-less
chip and bump up that MHz. That motherboard is *exact* same board
used in 20 and 25, 40 and 50MHz Macs including one low end Mac
server. (!!)

What is proper way to build up a reliable divide down TTL or
cmos circuit output just with 5V and ground and a oscillator? Say, I
divide 25 by 2 or 50 by 4 to get 12.5MHz.

I also have doc about details about replacing missing clock output
to run that ethernet Sonic chipset. That 10Mhz output is used there
also but there's the pads and holes, just move few parts around and
add few more parts which I have everything except this CPU frequency
that I have to make.

I tell you, that clever motorala engineers must found a way to make
040 series so efficient, even 16 MHz if there ever one existed blew
away 030 even at 40MHz. Right now doing my business on a LC III w/
stuffit uncoding those coded files. Slow as frozen sick snail even
LC III is stuffed w/ nice 540MB hd and spacious 20MB ram.

That really impresses me which I did worked with 486 and 386 machines
before and see performance differences is not as hot as like now.

Cheers,

Wizard
Received on Wed Mar 28 2001 - 15:52:26 BST