From: cwolf@iiic.ethz.ch (Christoph Wolf)
Subject: My IIci runs at 30MHz
Summary: ci upgrade to 30MHz by changing oscillator - experiences
Keywords: tuneup, soldering, MHz
Organization: Dept. Informatik, Swiss Federal Institute of Technology (ETH), Zurich, CH
Date: Mon, 28 Dec 1992 23:35:38 GMT


Hello speed-hungry ci-ownwers!

Yes, I have my ci running at 30Mhz instead of 25MHz.
After having read about upgrading IIsi's simply by replacing
an oscillator, I wondered (and some other people on the net
too) if this would be possible with a IIci. Last night I
desoldered the 50MHz oscillator, soldered in a socket and
plugged the oscillator back in its place. (This operation
seems to be quite simple, but actually it took me more than
an hour and quite a lot of nerves...)
Today I bought two oscillators, a 60MHz and a 66MHz. The 66MHz
(for a CPU speed of 33MHz) didn't work - the machine simply
did not boot. But the 60 MHz did! My ci runs at 30MHz now!

Ok, these are the good news, now the facts - and then the bad
news:

Speedometer 3.1 results:
         25MHz   30MHz
CPU    :  6.85    8.20
Math   :  9.15   11.04
Disk   :  2.15    2.16
Video  : 11.01   13.37
Overall:  7.01    8.36

The configuration: IIci, 20MB RAM (16 in bank B), 13"RGB on 
internal video, 210MB Quantum (3 partitions) internal, extensions 
off (shift key pressed at startup). No Nubus cards, no cache 
(still don't have one. Anybody happens to sell his cheap?).

The speedup is quite noticeable, but 20% won't blow your shoes 
off, of course.
But then I tested all the other things...
Internal video seems to no problem at all, but both my video 
cards show now and then some miscolored pixels. One of them is
a RELAX 19" 8bit card connected to a grayscale monitor, the 
other a Micron XCeed 24bit, both of them unaccelerated Nubus 
cards. I tried every possible combination with one and two 
monitors, using internal video or not and using different slots.
Nothing helped. I suspected the Nubus circuitry not to work
properly at the higher speed, but then, I currently have another
Nubus card, which works as before (This is a 6 node T805 
transputer card... what a pity it's not mine).
During 3 hrs of work I had one crash probably due to the higher
clock (Though it might be one of my 2 1/2 rows worth of 
extensions). 
But here are the severe problems: None of my terminal emulator
applications could connect to my modem, a Supra V32bis fax.
And printing was gone: Every application I tried reported 
"Personal LaserWriter not responding..." when I attempted to
print something. The serial port circuitry probably gets its
clock off the same oscillator as the CPU. But then, the 
MacRecorder connects through a serial port, too, and there
was no problem with this device. Anybody an idea?

All the problems went when I plugged the original oscillator 
in. Has anybody else made the same experiences?
Possibly 60MHz is still too high. As soon as I can get a 56 
or 58MHz oscillator,  I'll try this out.

---Chris


Sorry all you si owners: My 50MHz oscillator is not yet for
sale ;-)

****************************************************************
* Christoph Wolf                             cwolf@inf.ethz.ch *
* Auhof, 4314 Zeiningen, Switzerland                           *
****************************************************************
Newsgroups: comp.sys.mac.hardware