Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!ames!ptsfa!ihnp4!ihwpt!knudsen From: knudsen@ihwpt.UUCP Newsgroups: comp.sys.m6809 Subject: Re: Making old CoCo Disk Controllers work at 2 Mhz Message-ID: <1595@ihwpt.ATT.COM> Date: Tue, 14-Apr-87 19:06:16 EST Article-I.D.: ihwpt.1595 Posted: Tue Apr 14 19:06:16 1987 Date-Received: Thu, 16-Apr-87 00:53:03 EST References: <873@vaxb.calgary.UUCP> Organization: AT&T Bell Laboratories - Naperville, Illinois Lines: 31 Keywords: CoCo 3, Disk Controllers, 2Mhz troubles with OS9 Level 2 In article <873@vaxb.calgary.UUCP>, ingoldsby@calgary.UUCP (Terry Ingoldsby) writes: > Hear ye, hear ye all owners of old colour computer disk controllers that > have had troubles making them work at 2Mhz (with OS9 level 2). > > If you are having problems with your controller, try the above solution. If > the problem is not solved it may be necessary to make wiring modifications to > replace the CMOS with TTL or Hi-speed CMOS D latches. Does anyone know why > they used CMOS anyway? > Terry Ingoldsby Nice sleuthing there. Didn't know you could hack HW too! I wonder if you couldn't just replace the 74C chips with 74LS directly (no wiring mods). Why did they use CMOS? Good question. I wouldn't want it near an external bus -- easily damaged by static, and rather wimpy on the drive as you point out. Maybe Tandy wanted the rise/fall times on the bus to be sluggish, to cut down on RF emissions. Our FCC was very tight about that stuff on the early home computers. You probably know about the 3 capacitors and 1 resistor that should be removed from Coco 1s to help them run the Speed Poke. Sort of like bypassing/removing the smog control gadgets on car engines (does Canada have that stuff yet? Do you need it yet?) I have a friend who'll appreciate this info you posted. Thanks, mike k -- Mike J Knudsen ...ihnp4!ihwpt!knudsen Bell Labs(AT&T) Delphi: RAGTIMER CIS: " ~E(x):[is_lunch(x) && cost(x)==0] "