Msg: 6744 *Conference*
08-08-96 17:21:36
From: RON WIESEN
To : MIKE LANE
Subj: REPLY TO MSG #6742 (REPLY)
Sounds like a hardware problem Mike. If at this time the ExtRAM is removed and you turned off the memory backup power, left it that way overnight while the main power switch was OFF and no 6 volt adapter was attached, then at power on an "initial start" should have occurred. Unlike a mere cold-start, an "initial start" performs RAM write/read operations which leave alternate test patterns through most of RAM. You could check several places in RAM for this evidence. Can't remember exactly, but a think the pattern is ODD-BITs/EVEN-BITs (170/85) and the odd/even transitions are on 1,024 (1K) address boundaries. You know - 1,024 contiguous address contain the odd pattern then the next 1,024 contiguous address contain the even pattern, and so on throughout the RAM. PEEK around to see if these patterns are present. If so, you definitely got the "initial start". If not, something's amiss in the hardware world. Although I see no reason why the ExtRAM (assumedly now removed) could induce a hardware fault, you suggest that it is/was involved and has left TELCOM in line seizure. You may have more reason to think this than is evident from what you've disclosed here online. From what you have said here, my conclusion is that a hardware fault occurred and as a consequence you got the Jan 1900 cold-start which you mentioned. As I see it, all actions on your part after that are merely incidental and the hardware fault persists. One of the faults symptoms is TELCOM line seizure - others may be evident. Based on the only symptom evident now and an assumed hardware fault, the I/O port control of the telephone line relay is the directly related hardware. It's the 81C55 Peripheral I/O chip and sundry circuitry to the relay. So I would try to directly toggle the telephone line relay via OUT commands in BASIC while listening for the relay click-clack. Use OUT160,0 for line disconnect (relay not energized) and OUT160,1 for line connect. If you want to manipulate the Option ROM/Standard ROM selection hardware, use OUT224,1 to ungracefully switch to the Option ROM socket. I'm not sure what should happen with no installed Option ROM, but clearly you should lose control from BASIC. Perhaps a cold-start or "initial start" results from this abrupt and brutal action - I don't know. Of course OUT224,0 selects the Standard ROM which is already selected elsewise BASIC would be kaput! This should produce no noticible action. You could use OUT224,8 and OUT224,0 to toggle the tape cassette remote relay and listen for the click-clack. This toggle exercises port 224 but without altering the selection of the Standard ROM. So cruise around in BASIC and TEXT. See if other abnormalities are noticed. Tell us what you find. If something repeatable can't be found, then it's "wimpy" hardware. You know, ripple in the DC-DC converter, etc. If something more substantial can be found and is repeatible, Tracy Allen might relate symptom to fault quicker than less experienced folks like me. Get something he can sink his teeth into first, then ask him for help.