UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Computers

Notices

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

Closed Thread
 
Thread Tools
Old 27th Sep 2020, 8:53 pm   #1
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default SC/MP system from Practical Electronics April 1980

Chancing across a bunch of friendly retro-computer nerds on the forum has rekindled a long-standing interest in old 1970-1980 homebrew micro systems. I was particularly pleased to see that the National SC/MP still has a following - I built mine from a project designed by Andrew Aitken and published in Practical Electronics April 1980, in DJD's 'Microbus' column. It was a very limited system and programming was a very tedious operation using just binary keyswitches and LEDs. So I modified it quite a bit, adding extra memory, more I/O and a simple OS called 'Kitbug' in ROM with an RS232 interface to a terminal. I'd used a 4118 static RAM so it was easy to 'piggy-back' a 2716 EPROM since the pinout is identical.
Kitbug itself is very crude, having only three commands - 'T' to type out the memory contents, 'M' to modify memory, and 'G' to go to a program. I did some simple extensions to Kitbug, giving a formatted hex memory dump, tape load & store, and inline ascii string handling, and changed the RS232 to 300 baud (I cant read any faster than 300 baud ). Ultimately I intended to add NIBL which is a Tiny-Basic interpreter by National Semi, but at the time I couldnt find a ROM dump for NIBL so it never progressed beyond Kitbug. Very soon after this I built a Nascom so the SC/MP saw little use really but it still works here in 2020 and I occasionally fire it up just for old times sake. Its weird how op-codes committed to memory 40 years ago are somehow easy to recall from the old grey matter, yet I cant remember which day to put the bins out.

The "My Scamp loves me when I speak NIBL" scrawl on my 40-year-old notebook is a skit on the David Ahl BASIC games book which declared "my computer loves me when I speak BASIC" (or was it Dr Dobbs?)

https://www.youtube.com/watch?v=1WU7DbC8Sac

The Tandy 100 is a recent addition, I've only had that for 30-odd years Originally the SC/MP ran on an 'Elekterminal' built from an article in Elektor using the Thompson-CSF 96364 video chip. The Elekterminal is still up in my loft somewhere.

Oh, and if you were hesitant to click on the £15 chinese SC/MP chips on ebay, dont worry, they work great, in fact I think they could well be originals not clones.

...and incidentally, anyone who fancies building a really simple 1980-style BASIC machine should check out the "Jeff Graham Maximite" (google it, its superb).

More show & tell to follow - homebrew 6802 & Z80...

Cheers
Phil
Attached Thumbnails
Click image for larger version

Name:	philg_scmp.jpg
Views:	285
Size:	81.5 KB
ID:	216521   Click image for larger version

Name:	philg_scmp_annot.jpg
Views:	153
Size:	86.0 KB
ID:	216522   Click image for larger version

Name:	scmp_mods_philg.jpg
Views:	173
Size:	76.3 KB
ID:	216523  
Phil__G is online now  
Old 27th Sep 2020, 9:17 pm   #2
Mark1960
Octode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,038
Default Re: SC/MP system from Practical Electronics April 1980

Always good to see another old micro still running. The Tandy is a bit too modern for me but better than using a pc. It would be rally nice to see the Elekterminal running again.

I think with ebay you take your chances, I bought a set of three ins8060n supposed to be new old stock, but obviously previously soldered and remarked with the moulding marks on the bottom different but the printing on the top identical. Luckily I was able to get a refund after a bit of hassling them for a few days. In the end I was able to get some from a local shop for $10 each.
Mark1960 is online now  
Old 28th Sep 2020, 2:54 am   #3
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: SC/MP system from Practical Electronics April 1980

We're always interested in SC/MP machines here. I don't recall this one at all.
Karen O is offline  
Old 28th Sep 2020, 7:46 am   #4
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

Thanks for the background and history on this one it deserves to be here in a thread on its own rather than buried in another thread. Examples of them being built from the magazines and then customised like this is the story of the pre 1980s ready made computers era that will soon be lost if not captured.

As to the eBay chips - I had not had a problem until recently and then two I ordered were too thin and remarked and of course did not work - like Marc I managed to get a refund when I challenged them.

I have had quite good luck before then - I even had a few fakes in my last utsource order which has never happened before - but that was HC chips marked as LS and two RAM chips the latter could just be a misunderstanding in the chain from disassembly to resupply as they seem to have confusing marks - they do seem like old pulls.
Timbucus is offline  
Old 28th Sep 2020, 8:41 am   #5
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default Re: SC/MP system from Practical Electronics April 1980

Thanks all, personally I'd choose a desoldered pull from an old board over an uncertain 'new' source, but I have tried the 'recent' one and it seems fine, in fact I left it in the board rather than bother to swap it back. Back in the day I did have at least a couple of genuine spares, I've no idea where they went

Is there a way to embed videos properly so they dont show as a link? I tried the usual tags to no avail

Cheers
Phil

Last edited by Phil__G; 28th Sep 2020 at 8:55 am.
Phil__G is online now  
Old 28th Sep 2020, 7:22 pm   #6
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

I have (as you have) always had to link to the video rather than embed them. Great watch though - your corrupt returned echoed characters could be the top bit set - I think that has been discussed elsewhere. It was an artefact I had when I tried to use the SIO function to echo back what I was receiving - as it will be delayed by one bit duration.
Timbucus is offline  
Old 28th Sep 2020, 7:41 pm   #7
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default Re: SC/MP system from Practical Electronics April 1980

I hadn't really looked into it yet Tim, but you are absolutely right - it is the msb which is set, well spotted! I dont recall it happening on the Elekterminal, we'll see if/when I find it cant remember if internally its 7 or 8 bit ascii, its an 8-bit uart but I've a feeling only 7 are wired which would account for the 'clean' echo... setting the Tandy to 7 bits doesnt help, I tried all combinations.

I've a few AT28C16's which I bought to replace my 2716 eproms so when I get a mo I'll patch 'geco' to stop the bit 7 thing. Or strip bit 7 inline with a separate pic...

Last edited by Phil__G; 28th Sep 2020 at 7:48 pm.
Phil__G is online now  
Old 1st Oct 2020, 2:19 pm   #8
Slothie
Octode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,254
Default Re: SC/MP system from Practical Electronics April 1980

Quote:
Originally Posted by Phil__G View Post
Oh, and if you were hesitant to click on the £15 chinese SC/MP chips on ebay, dont worry, they work great, in fact I think they could well be originals not clones.
I bought 5 SC/MP INS8060 chips from a chinese seller and they didn'r look legit, and I tested 1 and it didn't work so I threw them in a box. I managed to get a "properly" marked NS SC/MP from a seller in Spain, so was OK. Later on I tested the other 4 chinese ones as a prelude to just throwing them out and they worked!
I think a lot of them are equipment pulls, as I read somewhere that NS sold a lot to manfacturers of medical equipment in the 70s and accreditation being the way it is the designs weren't changed fundementally for many years, hence the chips were produced for a long time and I wouldnt be surprised if the chinese "second sourced" them themselves.
Slothie is offline  
Old 1st Oct 2020, 2:49 pm   #9
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default Re: SC/MP system from Practical Electronics April 1980

The photo of the ones I bought do show socket marks so maybe. I dont mind, at least you can expect a pull to be genuine I sent the link in a PM Slothie. I wonder what other delights were on the boards they were pulled from?
If only there was a corresponding supply of pulled 8154s
Cheers
Phil
Phil__G is online now  
Old 1st Oct 2020, 11:18 pm   #10
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default Re: SC/MP system from Practical Electronics April 1980

Well, the 'bit 7 set on echo' problem with the 'kitbugged' David Aitken machine is fixed, tonight the problem got to me and it had to go!
I was only joshing when I said I might strip bit 7 with a PIC, but - never one to go looking for nutcrackers when theres a sledgehammer right there...

Its a 12F675, code attached, TTL in from Flag0 to GPIO1, pic output to the RS232 level converter is on GPIO0.
This is only in the outbound RS232 path from the scamp to the terminal of course, incoming RS232 is fine.

Flag0 used to go straight to the 741, now it goes via the pic. (I missed +/-12v supply from the 741 in the diagram)
Terminal echo is perfect now, no funny characters makes it much more pleasant to use!

Video: https://www.youtube.com/watch?v=WrBW0CxAU2w
Attached Thumbnails
Click image for larger version

Name:	IMG_20201001_234107.jpg
Views:	91
Size:	42.7 KB
ID:	216789  
Attached Files
File Type: zip kitbug_drop_bit7_300bd_12F675.zip (1.7 KB, 49 views)

Last edited by Phil__G; 1st Oct 2020 at 11:45 pm.
Phil__G is online now  
Old 1st Oct 2020, 11:31 pm   #11
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

I saw a post on FB recently that asked how often do we agonise longer how to do the most efficient thing when achieving the goal actually takes minutes once we take action... I now name this the Sledgehammer Hypothesis
Timbucus is offline  
Old 20th Oct 2020, 11:49 am   #12
Phil__G
Hexode
 
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 498
Default Re: SC/MP system from Practical Electronics April 1980

Just to conclude this thread, a couple of videos showing the working Kitbug system, and a fix for the echo problem:

https://www.youtube.com/watch?v=1WU7DbC8Sac

https://www.youtube.com/watch?v=WrBW0CxAU2w
Phil__G is online now  
Old 20th Oct 2020, 12:58 pm   #13
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

Excellent result not sure who the friendly retro nerds are
Timbucus is offline  
Old 24th Oct 2020, 4:03 pm   #14
Mark1960
Octode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,038
Default Re: SC/MP system from Practical Electronics April 1980

Quote:
Originally Posted by Phil__G View Post
If only there was a corresponding supply of pulled 8154s
Cheers
Phil
Does anyone have any recent experience of receiving parts sent from canada by canada post?

From what I see online there is a GBP 15 limit before VAT is charged and then GBP 135 limit before they charge other duty and taxes. What Iím not sure about is any service charges added by carrier for clearing customs.
Mark1960 is online now  
Old 24th Oct 2020, 4:49 pm   #15
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

In my experience (not from Canada, Most of Europe but, mainly China, although my Mum has had a few small parcels from her sister in Vancouver) the carrier only makes a charge when they have to pay the duty and taxes on your behalf. Then you get a £15 bill for them paying that on your behalf plus the cost charged in VAT and/or Import TAX - and that can get eye watering.
Timbucus is offline  
Old 24th Oct 2020, 4:58 pm   #16
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 9,768
Default Re: SC/MP system from Practical Electronics April 1980

That happened to me with the RAM for my issue VI MK14 replica - originally the 4 devices were priced at a reasonable 6 USD per chip, but by the time carriage, duty, and being charged for paying duty(?) were added on I think the cost to me was more like 50 GBP. This was from the USA though, not Canada.

I don't know what happens with stuff which has no indicated value (no invoice inside) ... or is the sender in CA obliged to put the value of the goods on the outside of the package anyway?
SiriusHardware is offline  
Old 24th Oct 2020, 5:39 pm   #17
Timbucus
Octode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,269
Default Re: SC/MP system from Practical Electronics April 1980

I think things by post not courier to a private address seem to usually get through unless they are obviously commercial. I had to laugh at one chip that turned up marked as "small plastic sheet". It had been opened by customs (big Customs tape re-sealing it) but, passed through with no charge.
Timbucus is offline  
Old 24th Oct 2020, 6:10 pm   #18
Mark1960
Octode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,038
Default Re: SC/MP system from Practical Electronics April 1980

Quote:
Originally Posted by SiriusHardware View Post
That happened to me with the RAM for my issue VI MK14 replica - originally the 4 devices were priced at a reasonable 6 USD per chip, but by the time carriage, duty, and being charged for paying duty(?) were added on I think the cost to me was more like 50 GBP. This was from the USA though, not Canada.

I don't know what happens with stuff which has no indicated value (no invoice inside) ... or is the sender in CA obliged to put the value of the goods on the outside of the package anyway?
Using canada post for small packet is about $12, but thats without tracking. Including tracking takes that up to about $35. Which is not really worthwhile if trying to stay below vat limit.

The sender has to create an invoice on canada post standard form and I think I would include a copy of invoice from my supplier rather than risk customs using an ebay search.

Iíve had similar issues with service charges for import duty on pcb orders from jlcpcb to canada with dhl, fedex are similar but not quite so bad, but then their shipping cost is higher.

If someone would like to give this a try then send me a PM and Iíll send more details on what I can get from local supplier.
Mark1960 is online now  
Closed Thread

Thread Tools



All times are GMT. The time now is 2:17 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.