Date: Tue, 4 May 1993 03:49:58 -0700 (PDT)
From: Guy Kuo <[email protected]>
Subject: IIsi-clock-mod-poll.txt

Report on poll of users who have upgraded their IIsi clock oscillators for
higher speed. Suggest placement in reports folder.

------------------------------
This poll was conducted to help users decide whether or not to alter their
IIsi clock oscillator. I have attempted to gather as many case histories as
possible to find some estimate of success and risk. The number of replies
probably shows how rare this modification is but give the impression that
success rates may be higher than the previous 80% estimate. 25 of 25
machines were able to run at 25 mhz when no add on boards were present.
This is not a scientific survey but it is the best we have to work with.

Thanks to all who contributed to this poll.


Issues:

       Speed) 25 mhz to 27.5 mhz appears to be the norm for machines
               without add on cards. All reported machines were able to
               use 25 mhz as long as no add on cards were present. Several
               Apple cards were in use. No machine with the Nubus adapter
               was able to go faster than 25 mhz. One wasn't even able to
               achieve 25 mhz with the Nubus adapter in place

               At speeds >= 30 mhz, the startup sound may crackle
               and hi density floppy disk problems have been reported.

               Note: Unless specifically listed below, machines were not
                       tested with a higher speed clock to failure. Hence,
                       the 25 mhz operational machines may well work at
                       higher speeds.

       Damage) One user reported pulling out the plating of one pad. This
               was repaired and the machine is operational. One other
               reported pulling the pin out of the original clock
               oscillator during desoldering. There is one second hand
               report of a user putting a gash in the motherboard with a
               slipped soldering iron.

               No reports of static discharge damage.

               No reports of high speed operation causing damage.

               Then again, I also don't have any reports from users of
               defective parachutes.

       Add on boards) Compatibility appears to be a problem with Apple
               Nubus Adapters. Several other add on boards have been used
               with success. See case histories

       Heat Sinks) Virtually all modified machines had a heat sink
               installed. These were often the TO-220 style power
               transistor type. Some used epoxy. Some used a dab of heat
               sink compound with a dab of cyanoacrylate glue. There was
               also use of a clamp with a bolt through the hole in the
               motherboard.

               James MacPhail <[email protected]> is gathering evidence
               which indicates a heatsink is advisable



Case Histories:

All speeds are the effective CPU speed (1/2 of clock oscillator). All reported CPU versions were 20 mhz.

1)  27.5 mhz operational. Ran for 10 minutes at 31 mhz before crashing.
   No FPU or other add on card
   Heatsinked CPU only
   On 24 hours/day
   No damage during installation

2)  27.5 mhz operational without Apple Nubus adapter. 25 mhz top speed with
       Apple Nubus card installed
   Heatsinked CPU only
   On 24 hours/day
   No floppy problems
   No damage during installation

3)  27.5 mhz operational. Unable to boot at 31 mhz
   Heatsinked CPU only
   No floppy problems
   No damage during installation

4)  25 mhz operational
   Works with the following two configurations

               a)      Realtech FPU adaptor card
                       Realtech Cache card
                       SuperMac 8*24 PDQsi

               b)      SuperMac FPU adaptor card
                       SuperMac Video Spigot
                       SuperMac 8*24 PDQsi

5)  33 mhz operational
   Fuzzy startup sound
   Problems with hi density disks

6)  33 mhz operational
   Fuzzy startup sound
   Heat sink on CPU and chip to right of CPU

7)  25 mhz operational. Occasional crash at 33 mhz

8)  25 mhz operational.
   Using FPU rated at 16 mhz without difficulty

9)  25 mhz operational.
   PDS adapter with a Spectrum 24PDQsi graphics card and a
   VideoSpigot, a 20MHz FPU
   Heat sink on CPU

10) 25 mhz operational. 33 mhz failed after several hours.

11) 25 mhz operational
   5/80+quicksilver/fpu(only upgrade)

12) 25 mhz operational. Tried 33 mhz - system won't start.
   Heat sink on CPU
   Configured with
        RealTech FPU/adapter card
        Supermac 8*24 PDQsi
        Realtech cache.
   CPU on continuously - no problems.
   Floppy works fine at 1.4MB @ 25 mhz

13) 25 mhz operational
   Heat sink on CPU

14) 25 mhz operational
   Heat sink on CPU

15) 25 mhz operational
   Heat sink on CPU

16) 25 mhz operational
   Heat sink on CPU

17) 25 mhz operational
   Heat sink on CPU
   On 17-19 hours per day

18) 25 mhz operational
   Heat sink on CPU + cooling fan
   No floppy problems at 25 mhz

19) 20 mhz operational. Bombed soon after startup at 25 mhz with Nubus
     Adapter
   20 mhz rated CPU
   RAM 70 ns in slots, 80 on motherboard

20) 25 mhz operational
   Heat sink added to CPU later. No damage while unheatsinked.
   Apple Nubus adapter with FPU installed.

21) 25 mhz operational
   Heat sink on CPU

22) 25 mhz operational
   Heat sink on CPU

23) 25 mhz operational
   Heat sink on CPU

24) 25 mhz operational
   Heat sink on CPU

25) 30 mhz operational 5/240 with Nubus adaptor
   Ran 1 week at 31 mhz
   Heat sink on CPU
   Sound does not crackle at 31 mhz
   Floppy drive recognizes HD disks at 30 mhz but will not read properly
   Add on RAM is 70 ns



Guy Kuo <[email protected]>