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Xref: sserve comp.sys.ibm.pc.hardware:34040 comp.unix.bsd:6908 Path: sserve!manuel.anu.edu.au!munnari.oz.au!sgiblab!sgigate!olivea!uunet!cs.utexas.edu!wupost!udel!rochester!rit!isc-newsserver!ritvax.isc.rit.edu!AJB8886 From: ajb8886@ritvax.isc.rit.edu Newsgroups: comp.sys.ibm.pc.hardware,comp.unix.bsd Subject: Re: Question on Diamond Clock Synthesizer Message-ID: <1992Oct21.091159.18807@ultb.isc.rit.edu> Date: 21 Oct 92 09:11:59 GMT References: <1b7tmgINNi06@agate.berkeley.edu> <1992Oct19.082420.16353@Informatik.TU-Muenchen.DE>,<1992Oct19.151409.24581@osf.org> Sender: news@ultb.isc.rit.edu (USENET News System) Reply-To: ajb8886@ritvax.isc.rit.edu Organization: Rochester Institute of Technology Lines: 72 Nntp-Posting-Host: vaxa.isc.rit.edu In article <1992Oct19.151409.24581@osf.org>, kenny@osf.org (Kenneth Crudup) writes: >In article <1992Oct19.082420.16353@Informatik.TU-Muenchen.DE> >roell@informatik.tu-muenchen.de (Thomas Roell) writes: > >>There are a few limitations like the highest frequency the chip can produce >>(without emitting that neat smoke) > >Yeah, like maybe CLK/1???? > >.... > >>So what would happen if you programm the PLL wrong and blow your board ? > >ONCE MORE- explain to me exactly how programming a divider value into a >chip WILL BLOW IT!!! > >If you run some chips (the i486 comes to mind) at higher speeds, they will >dissipate more power, and could (BIG emphasis on could) overheat to the >point where the chip becomes unreliable, but NOT fail. No chips on my >SS24x run anywhere near warm, and definately less than the heat generated >by my AMI 386-40. In order to get any type of useful divider resolution, >the clock freq in has to be quite high. If you "program the PLL wrong" >so that you generate one of these "chip-blowing high frequencies" YOUR >MONITOR WILL SHOW IT (or I guess you'll tell me, despite my kicking holes >in that theory, that it will blow your monitor too?) > >Either give me a full technical explanation, or quit talking shit! How much >*is* Diamond paying you? > > -Kenny >-- >Kenneth R. Crudup, Contractor, OSF DCE QA >OSF, 11 Cambridge Center, Cambridge, MA 02142 +1 617 621 7306 >kenny@osf.osf.org OSF has nothing to do with this post. > Religion: The longest-running gag ever played on Mankind. Ahem. I can't speak myself for the full technical explaination, but I've certainly seen monitors go up in smoke (and more than a few flyback transformers explode in a spectacular lightshow) after being driven at a frequency beyond the specified limits of the monitor for more than a few minutes. I won't speculate as to why, as I don't claim to be a video monitor design engineer. But I will confirm that it happens. It does seem resonable that the converse would be true; ie. if a clock synthesizer can be programmed to generate frequencies beyond the limits of the chips on the card, then the card will indeed go up in smoke, in much the same way that your example 386-40 would go up in smoke if you were able to set a hypothetical clock synthesizer for it to say, 50 or 60Mhz. And I would suggest you test the temperature of the chips on your card not when driving it at a low clock (ie. 640*480), but rather at a high clock such as 1024*768 non-interlaced at 72Hz refresh. I would indeed be interested to know whether the chips still run as cool as you claim. Note however, that I am not claiming that the Diamond clock CAN be programmed to generate frequencies beyond the limits of the chips used on the card (I have no idea what safeguards, if any, Diamond may have implemented). I merely assert that attempting to run a device beyond its rated clock will indeed cause overheating (depending on how much margin for error the engineers allowed for) and in extreme cases will result in a chip going up in smoke. Thus, if a clock synthesizer can be programmed to generate a clock beyond the ratings of the system, it's certainly reasonable to assume that you can "blow the card" by incautious manipulations of a programmable clock synthesizer. Alex