5 Aug
2016
5 Aug
'16
11:54 a.m.
On Friday (08/05/2016 at 11:23AM -0700), Brad H wrote:
Okay thanks. ?I gues where I'm getting confused is Michael Holley's guide to new
6800 users says because of the 6810 being cut you want RAM at $A000.. what you're
suggesting sounds like the opposite? ?Maybe I'd better reread those instructions.
MIKBUG and SWTBUG need the RAM at $A000 not $0000. RAM at $A000 was
the original MEK6800-D1 reference design for which MIKBUG was invented
and the MP-A is likely derived.
As an aside, I have what I think is a kinda rare EXORBUS to SS-50
adapter that SWTPC may have made during development of the machine so
that an MEK6800-D1 could be used as the CPU board on SS-50 bus. It is
an interposer with 86-pin EXORBUS socket on the top and (5) 10-pin MOLEX
on the bottom which mate to one of the SS-50 50-pin backplane locations.
It has SWTPC logo on it so I don't think it was a third-party deal.
Chris
-------- Original message --------
From: Brent Hilpert <hilpert at cs.ubc.ca>
Date: 2016-08-05 10:52 AM (GMT-08:00)
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Subject: Re: SWTPC 6800
On 2016-Aug-05, at 9:55 AM, Brad H wrote:
--
Chris Elmquist
3) Ah, this may be part of my problem.? I don't quite understand memory
addressing yet.? The instructions said you needed RAM at A000 if the 6810
chip was disabled (which it appears to be, the correct trace is cut).? My
machine has 4 RAM boards.? 2 are MPM, 2 are 16K DRC boards.? For whatever
reason, the DRC boards are config-ed to be first (0000-3FFF) and second
(4000-7FFF).?? Trying to strip the machine down and have as little RAM as I
could get away with, I just installed the single board at 0000-3FFF.? These
boards are (thank god) socketed, so I have some means of testing and
removing RAM.? The MP-M boards are not socketed, so I don't want to mess
with those until I have to.? I could config the second DRC board for the
$Exxx-$Fxxx and shove it in there.
Don't take my word on the specific address, I should have just said you need some RAM
in high mem.
The 6810 was there to fulfill that need of RAM for the xxxBUG monitor.
You might reenable it, or config a RAM board to cover that range (A000? to ?).
But if you use a RAM board you have to config it so it doesn't extend up into
(overlap) the ROM and IO address space.
(I have a memory map for this on another machine not set up at this time).
(For purposes of exercising the xxxBUG monitors you don't need memory down at
$0000.)