SWTPC 6800

Brent Hilpert hilpert at cs.ubc.ca
Sat Aug 6 00:47:05 CDT 2016

Do you have some RAM at $A000+ yet?
That's all that should matter as far as required RAM goes.

Presuming this is the holley page you were referring to:
he does mention RAM needed at A000 for the BUGs, as Chris and I have been saying.

Without RAM there there's no stack for return addresses for subroutines executed in the BUGs, so execution could head off to wherever.

On 2016-Aug-05, at 10:23 PM, Brad H wrote:
> Okay so.. I decided to try the MP-C board out, just for kicks.  No change.
> Then I decided to add one of the RAM boards.. the next one up in addresses.  Got a little bit when I powered on.  Added one of the old MPM boards.. one that has memory chips all piggybacked on one another.  Now when I powered up, the system was sending four or five characters at a time, linefeed, four or five characters at a time, linefeed ad infinitum.  I added the final MPM board.. zero.
> So.. I think we do have some ram problems.. most likely.  I'm thinking it would be easiest to concentrate efforts on the socketed RAM boards.. test all the RAM out.  I'm going to read up on addressing and try to understand a bit better what is going on.  I'm thinking maybe I need to reconfigure the addressing on one of the boards to match whatever that overstuffed MPM board is set to.
> Until I get an oscilloscope.. fooling around is about all I can do here.
> Sent from my Samsung device
> -------- Original message --------
> From: Chuck Guzis <cclist at sydex.com> 
> Date: 2016-08-05  3:55 PM  (GMT-08:00) 
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> 
> Subject: Re: SWTPC 6800 
> On 08/05/2016 02:15 PM, Brad H wrote:
>> I think I will have to figure out how to do that.  Additionally I
>> have one of those PC based oscilloscopes on the way.  I don't know
>> how to use them 100% but I'm about to learn I guess. :)
>> I have one more question for you guys -- I have a few CT-1024
>> terminals and would really like this system to work with one of
>> those.  However, all of the CTs are quite delicate and are set I
>> think for 7, E, 2 @ 110 baud via soldered jumpers.  I'm a bit
>> reluctant to try pulling them apart to get in there and fix that.  Is
>> there a way to change the parity, etc settings on the SWTPC to match
>> the terminal?  Is it necessary?
> Well, 110 bps is a bit on the slow side--great for teletypes, not so
> much for video terminals.   But you'll have to change the hardwired
> jumpers--the UART used in the CT1024 is not software-programmable.
> If this were my unit, I"d probably solder some pins into the pad holes
> and then either use slide on jumpers or wirewrap to set the
> characteristics.  That way, when changing things around, you won't be
> stressing the PCB.
> Something like this:
> http://www.ebay.com/itm/10PCS-20CFemale-to-Female-1-Pin-Plug-Jumper-Cable-Wires-Multicolor-K-/262158878688?hash=item3d09e307e0:g:B-MAAOSwwE5WVLR6
> Search on "female jumper wires"

More information about the cctalk mailing list