SWTPC 6800

Brad H vintagecomputer at bettercomputing.net
Fri Aug 5 13:23:49 CDT 2016

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.

Sent from my Samsung device

-------- 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:
> 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.)

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