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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 6th Jul 2021, 11:11 am   #1
Timbucus
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Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,091
Default Scrumpi 2/3 developments and Scrumpi 4!

For those who followed the original Scrumpi 1 reconstruction thread you know that I wanted to move on via the Scrumpi 2 to eventually the 3.

Several e-mails to The Computer Sheds, who have a Scrumpi 2 have not resulted in any photos of the board and the website I set up had only a few contacts (which I missed for a while due to a mail routing error..). One contact said he had some 2 and 3 material but, as yet has not come back to me with them, either.

I have established that the Case used on the Scrumpi 3 from a recent perusal of some attic found Maplin's magazines was a Vero Type 502 case - part no 21098F - 550x340x120 with a 430x115 panel and Max PCB of 160x220

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One of the most interesting contacts though from the website was an e-mail from Paul Robson who had a few years ago been following a similar reverse engineering path to me, including disassembling the fragments of code in photographs. That resulted in a White room reconstruction of the Scrumpi 3 EPROMs (they function like the described system but, do not preserve the actual known code)... to test this he wrote an emulator as well which he just made public with the EPROM code and I have recently got working on my Linux machine - very creepy playing with a Scrumpi 3...

https://github.com/paulscottrobson/scrumpi3

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Finally an interesting finding from continuing research shows from PE Sep 1978 that JMK planned a SCRUMPI 4 - P.E. probably got the news from the Computer Weekly news update in Jul 1978...

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If you want to play with the emulator the docs are a bit sketchy so here is what I have worked out:

Build
-------

Need to install SDL dev to get it built for Linux

e.g. https://learncgames.com/tutorials/ho...-sdl-on-linux/

just 'make' in the emulator sub dir from the git clone makes an executable.

Operation
-------------

./scrumpi3
F5 to start

Simple program - place XPPC P3 at first byte of user RAM, return to monitor and run
this will do the register and stack dump display seen in one of the photos.

I 7F80 3F
>
G 7F80

Controls
-----------
F1 reset machine (i.e. PC=0000)
F2 home
F5 run emulator
F6 Break back to debug screen - hard breakpoint

TAB - Show

F7 - Step
F8 - Step over
F9 - Breakpoint - set at current displayed address will drop
back to emulator when SC/MP gets to that address

ESC will exit back to OS
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Old 6th Jul 2021, 4:15 pm   #2
Mark1960
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Location: Kitchener, Ontario, Canada
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Default Re: Scrumpi 2/3 developments and Scrumpi 4!

I was wondering how the scrumpi 4 would handle keyboard and display if it was based on the standard NIBL rom from National Semiconductors, but then reading the article snippets again I noticed the bit about requiring a terminal and possibly using a scrumpi 3 for that. This would seem to mean that the scrumpi 4 was unmodified NIBL which would make it easier to recreate with the same facilities.
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Old 6th Jul 2021, 7:56 pm   #3
Timbucus
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Default Re: Scrumpi 2/3 developments and Scrumpi 4!

Yes - they seem to suggest that it would rely on an external terminal - I suppose as it used the standard large NIBL ROM he would have no choice as the Scrumpi 3 architecture would have got in the way but, a basic Scrumpi 3 at 189 with case and PSU was effectively a useful Dumb Terminal already by then in its basic 128 byte model with no RAM expansion etc.

I envision it as a single large PCB a bit like the Nascom or the Triton as he does not mention a rack mount or anything like the ETI S68 used which was originally the first Scrumpi design adapted to the 6800 chip.
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Old 6th Jul 2021, 10:16 pm   #4
Mark1960
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Default Re: Scrumpi 2/3 developments and Scrumpi 4!

I think it would have been uncompetitive against the nascom 1 at that price. Though the starter kit for Nascom 1 did not include basic, for the scrumpi 4 @ 150 + scrumpi 3 at 189, I think the Nascom 1 could have been expanded to a much more capable system.
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