Date: Tue, 4 May 1993 03:49:58 -0700 (PDT) From: Guy Kuo 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 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