iisi clock poll results long 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 estimate of machines were able to run at 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 mhz to mhz appears to be the norm for machines without add on cards all reported machines were able to use mhz as long as no add on cards were present several apple nubus cards were in use no machine with the nubus adapter was able to go faster than mhz one wasn t even able to achieve mhz with the nubus adapter in place at speeds of and mhz the startup sound is distorted 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 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 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 case histories all speeds are the effective cpu speed of clock oscillator all reported cpu versions were mhz mhz operational ran for minutes at mhz before crashing no fpu or other add on card heatsinked cpu only on hours day no damage during installation mhz operational without apple nubus adapter mhz top speed with apple nubus card installed heatsinked cpu only on hours day no floppy problems no damage during installation mhz operational unable to boot at mhz heatsinked cpu only no floppy problems no damage during installation mhz operational works with the following two configurations a realtech fpu adaptor card realtech cache card supermac pdqsi b supermac fpu adaptor card supermac video spigot supermac pdqsi mhz operational fuzzy startup sound problems with hi density disks mhz operational fuzzy startup sound heat sink on cpu and chip to right of cpu mhz operational occasional crash at mhz mhz operational using fpu rated at mhz without difficulty mhz operational pds adapter with a spectrum pdqsi graphics card and a videospigot a mhz fpu heat sink on cpu mhz operational mhz failed after several hours mhz operational quicksilver fpu only upgrade mhz operational tried mhz system won t start heat sink on cpu configured with realtech fpu adapter card supermac pdqsi realtech cache cpu on continuously no problems floppy works fine at mb mhz mhz operational heat sink on cpu mhz operational heat sink on cpu mhz operational heat sink on cpu mhz operational heat sink on cpu mhz operational heat sink on cpu on hours per day mhz operational heat sink on cpu cooling fan no floppy problems at mhz mhz operational bombed soon after startup at mhz with nubus adapter mhz rated cpu ram ns in slots on motherboard mhz operational heat sink added to cpu later no damage while unheatsinked apple nubus adapter with fpu installed mhz operational heat sink on cpu mhz operational heat sink on cpu mhz operational heat sink on cpu mhz operational heat sink on cpu guy kuo guykuo u washington edu
