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 <hilp...@cs.ubc.ca> > Date: 2016-08-05 10:52 AM (GMT-08:00) > To: "General Discussion: On-Topic and Off-Topic Posts" > <cctalk@classiccmp.org> > Subject: Re: SWTPC 6800 > > On 2016-Aug-05, at 9:55 AM, Brad H wrote: > > > > 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.) > -- Chris Elmquist
