Back to overclocking! So I bypassed the crystal and clocked the unit directly from a function generator. Unfortunately the clock chip (RP5C01) is simply too slow at anything above ~9.5Mhz, however the T200 it's self will run right up to 12Mhz!
Was hoping for a newer generation pin compatible chip, but looks like none were produced. Though the protocol doesn't look too hard to replicate, but don't think I'll go to that trouble. Now to figure out what to do with the EXTRam, or just use the sleeve for a 27c256 ROM, or ditch it for a REX. On Fri, Jul 27, 2018 at 1:43 PM Andy Lawrence <[email protected]> wrote: > After the fun with my T102 I decided to continue the fun with a busted > T200 off eBay. After a complete re-cap, fixing lots of keyboard traces, > huge mounts of cleaning I now have a nice functional T200! This unit came > with the RAM fully populated and an EME ROM, which doesn't seem to do > anything, calling 63012 locks is up, and 63013 returns OK with nothing else > obvious. No NiCad or Y2K mods yet cause I ran out of parts, waiting on > Digikey. > > Well I got bored waiting on Digikey and thought, how fast can this thing > go, so I swapped the 4.9151 crystal with a 10Mhz (all I had in-stock), and > it boots and runs! So I quickly threw this program together, prime number > example I found online modded to time the loop: > > 1 POWER CONT > 10 CLS > 20 PRINT "LIMIT"; > 30 INPUT L > 31 HH$ = LEFT$(TIME$,2) > 32 MM$ = MID$(TIME$,4,2) > 33 SS$ = RIGHT$(TIME$,2) > 37 SEC = VAL(SS$) + (VAL(MM$) * 60) + (VAL(HH$) * 3600) > 40 FOR N = 3 TO L > 50 FOR D = 2 TO (N-1) > 60 IF N/D=INT(N/D) THEN GOTO 100 > 70 NEXT D > 80 PRINT N; > 90 GOTO 110 > 100 PRINT "."; > 110 NEXT N > 111 HH$ = LEFT$(TIME$,2) > 112 MM$ = MID$(TIME$,4,2) > 113 SS$ = RIGHT$(TIME$,2) > 114 SECE = (VAL(SS$) + (VAL(MM$) * 60) + (VAL(HH$) * 3600) - SEC) > 117 PRINT "Duration = "; SECE ; " Seconds" > 120 END > > Duration factory = 43sec, duration overclocked = 21sec! (with an input of > 100) > > It isn't completely stable, sometimes I have to power it on 2-3 times, but > once on it doesn't seem to have any trouble, aside from the clock resetting > on occasion. I've not yet studied the schematic to determine if it's > because 10Mhz isn't a multiple of the factory 4.9152, or because it's > simply too fast to read properly, but I'll figure it out. I ran the > above to 1000 a few times without issue or any lock ups. File transfer > even works if I set my PC to 2400bps and the T200 to 1200. > > Overclocked comes at a 20mA over stock hit. > > Fun fun, happy Friday. > BR, > Andy > > > > > > -- projecthuh.com Never underestimate the carelessness of boredom... Most people prefer Windows because most people are idiots...
