More SC/MP - Science of Cambridge MK14 clone

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Phil_G
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More SC/MP - Science of Cambridge MK14 clone

Post by Phil_G »

Over on the vintage computer forum theres a lot of interest in recreating obsolete and unobtainable old microprocessor training, development and hobby systems.

Its exactly the same nostalgia drive that compels us to fly Galloping Ghost and pretend escapements :D

One extremely clever member has not only emulated the National SC/MP chip hardware on a PIC877, but used this emulation to recreate the Science of Cambridge MK14. Although my own board isnt yet fully populated, I've got my MK14 clone running and I'm just about to start making the NIBL machine.

Other fascinating projects include a ZX81 clone and a Commodore 64 clone, and another SC/MP project where the emulated SC/MP runs National Industrial Basic Language (NIBL).

They also recreate these old systems using original parts and diagrams, there's a complete SCRUMPI, a SCRUMPI-2 almost finished and a SCRUMPI-3 on the way. There are no known original SCRUMPI-3's in the world so this is really important work to preserve the accomplishments of these early days. Another running project is the visual display unit for the MK14 - again there are very few originals left.

Heres the SoC MK14 clone, anyone recognise it? It runs all the SC/MP machine code examples from the SoC instruction manual, and with cycle-perfect timing. It does need a keyboard overlay though :D



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Edit: Even a quickie keyboard overlay makes it so much easier to key!


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This is a clone of the Science of Cambridge MK14 which first appeared in 1977 as a kit for electronics enthusiasts who wanted to learn about microprocessors. The SC/MP ("Simple Cost-effective Micro Processor") has a really nice instruction set, small enough to remember but powerful enough for complex tasks. It has an accumulator, an X register (which is a bit like an eXtra accumulator), three 16-bit pointer registers which can have a +/- 128 offset or use the X register as an offset (ideal for addressing tables where X acts as a loop counter AND an offset) and a status register which has some bits actually brought out as hardware outputs.

The clone runs the original firmware as provided by National Semiconductors to Chris Curry and Clive Sinclair, which was identical to Nationals own 'Introkit' system.
The SC/MP microprocessor chip is becoming a rarity now and Karen Orton, an incredibly clever programmer, has accurately emulated the SC/MP chip using a modern PIC16F877. Even the emulation timing is cycle perfect.

Note that its not the overall MK14 system that is emulated - even more clever, its the actual SC/MP microprocessor chip itself, and it runs the original, period SC/MP code that was resident in the DM74S571 PROM chips of a genuine 1977 MK14. You could build any SC/MP based system using Karen's PIC chip as the processor.

I regret selling my own MK14 decades ago, so I made one of Karen's clones - and as expected it operates exactly like the original. It runs all the examples in the MK14 manual and has the benefit that it retains the last program entered during power off. It can be built for a fraction of the £39 cost of the original MK14 kit!

(Eagle-eyes will notice that I cocked up the 7-segment pattern at address 0F53 by pressing a wrong key!
... I didnt notice until after uploading the video... :D )


Advertising always used an 'artists impression' rather than a photo, collecting orders to fund development wasnt unusual...


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I've sent for some PCBs to see if I can recreate my own Motorola 6800 system from 40 years ago...


More to follow...
Cheers
Phil
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