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Xref: sserve comp.sys.ibm.pc.hardware:33865 comp.unix.bsd:6801 Newsgroups: comp.sys.ibm.pc.hardware,comp.unix.bsd Path: sserve!manuel.anu.edu.au!munnari.oz.au!uunet!noc.near.net!news.cs.brandeis.edu!ST923150@pip.cc.brandeis.edu From: st923150@pip.cc.brandeis.edu (Benjamin A. Tober) Subject: Re: Question on Diamond Clock Synthesizer Message-ID: <1992Oct19.223502.20477@news.cs.brandeis.edu> Sender: news@news.cs.brandeis.edu (USENET News System) Reply-To: st923150@pip.cc.brandeis.edu Organization: Brandeis University References: <1992Oct19.082420.16353@Informatik.TU-Muenchen.DE> <1992Oct19.151409.24581@osf.org> <1992Oct19.190736.11988@fcom.cc.utah.edu>,<1992Oct19.215256.5037@osf.org> Date: Mon, 19 Oct 1992 22:35:02 GMT Lines: 29 I agree with the esteemed Mr. Crudup. It might be possible to overheat component(s) on the video board by using a very small divisor, if the board were so poorly designed as to have components that cannot tolerate a frequency that _can_ be generated. Historical note: The Tandy CoCo had a problem like this: The processor and bus local to the processor were driven by a programmable oscillator which could run the processor at speeds faster than its design parameters. It is, thus, one of the few machines on which there is a known way to nicely smoke the motherboard using a two-line program written with the built-in BASIC interpreter, but I digress... So, as to whether it is possible to damage the board by misprogramming it, the answer is yes if it was so designed. Now, on the other hand, as for destroying the monitor, if it is a multifrequency monitor (i.e.- the kind usually used with such a board) then it is extremely unlikely that malprogramming the clock generator could cause damage. Multifreqency monitors _attempt_ to match the output frequency of the board driving them, but only within a certain range. In general, they are designed to just "give up" on frequencies outside of the intended range. This would usually be witnessed as rolling or other general unintelligibility of the display... Now, as for damaging a fixed-frequency monitor, this is very much possible. IBM fixed-frequency monochrome monitors (which were meant to be used with the MDA) could be caused to overheat by certain screen-blankers which blanked the screen by turning off the sync signals to the monitor. So, certainly, when dealing with fixed-frequency monitors, care must be exercized. In summary, whether it is possible to damage the board by misprogramming the clock generator, only some EE(s) at Diamond would know... or, if you want to hardware reverse-engineer the beast, be my guest. As for damaging multifrequency monitors, I would place money on this not being possible. -ben