Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!decwrl!deccrl!news.crl.dec.com!shlump.nac.dec.com!tkou02.enet.dec.com!wpowz.enet.dec.com!zambotti From: zambotti@wpowz.enet.dec.com (Walter Zambotti DEC) Newsgroups: comp.os.os9 Subject: Re: High Speed OS9 Level II on a CoCo3 Keywords: disk drive, high density, os9 Message-ID: <1991Mar18.020708.3267@tkou02.enet.dec.com> Date: 18 Mar 91 02:07:08 GMT References: <1991Feb13.044240.16381@tkou02.enet.dec.com> <2759@batman.moravian.EDU> Sender: news@tkou02.enet.dec.com (USENET News System) Reply-To: zambotti@wpowz.enet.dec.com (Walter Zambotti DEC) Distribution: usa Organization: Digital Equipment Corporation Lines: 65 Hi Dave, read your followup. Understand what your asking! > If I hack that trace, pop in the old crystal with a /4 circuit, will the > video still sync up to the CoCo3 bus??? I figured the coco and the GIME > might not like to chat anymore because of bus timing problems.... From this I gather you want to hack the clock trace to the GIME because you feel that this is where the video clock frequency would best be altered? I would not have done it this/that way. The 6809 and the GIME should both have the same clock chip. And I am suggesting that the video clock frequency be hacked at some point after it leaves the GIME chip. I would support your reckoning that if the GIME and the CoCo had mismatching frequencies then there would be contention on the bus. If it is not possible to hack the clock frequency after it leaves the GIME because clock frequencies are not relevant at that section of the video circuitary then you may have to alter the actual video frequency (as apposed to the clock frequency) at some point in the final stages of the video output circuitary. > If that is all that is required, then I could pop in a few chips into a > cheapo piece of perf board with the old crystal and get the whole thing > working. Could I use TTL or CMOS chips with that clock crystal for a > divider circuit? Can't say! Only someone who attempts the mod would be able to shed some light on that. And at the moment Dave it sounds like your one of the only few (if not one) who is attempting this at all. My only input on this is to : Hack the video circuitary on the CoCo sometime after it leaves the GIME, whether by clock frequency shifting or video frequency shifting. Keep the relative clock frequencies between the GIME and the 6809 the same, i.e. if you double one then double the other. Be brave. Dave it is you (and not I) at the fore front of this exciting modification. You may have to experiment until you get what you want. > In article <1991Feb13.044240.16381@tkou02.enet.dec.com>, zambotti@wpowz.enet.dec.com (Walter Zambotti DEC) writes: > > >OK... I tried the switch... I swapped crystals on the CoCo3 with 512K to get > > >a boost in speed... no problem, it worked most of the time ... I did it > > > [...] Sorry but I never wrote any of this. I only replied to the above. I did write this though : > Instead of hacking your monitors to match the speed of the faster CoCo > why not make the video output section of the CoCo match the original > speed of the monitor. i.e. cut the trace that supplies the clock to the > video circuitry and "glue" in the old crytsal (plus or minus any > dividers) from the CoCo on to the cut trace/pin. regards, Walter