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Thread: SoC MK14

  1. #1
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    Default SoC MK14

    This Christmas I did a bit of a purge and raised about $1000US to put towards something 'new'. So I bid on and managed to win a rare US-located original MK14!

    https://drive.google.com/drive/folde...Qi?usp=sharing

    Kind of excited - it's from the original owner, and he just found and is including the original monitor PROMs as well as the upgraded ones already installed. I don't know what Issue it is but he thinks it was one of the earlier ones - his girlfriend bought it for him on a trip to the UK in early 1978. Apparently it's fully working, apart from the keyboard which he bypassed years ago.

    Price wise these seem to be all over the place. One lucky guy got one recently for 99 pounds on a Buy It Now. But generally they seem to be north of $1000USD, a couple I have recorded went for $1300-1400. Pretty crazy considering what it is.

    I had thought about going for a replica but I'm more of an 'originalist'. I don't object to paying a few bucks when the provenance is well established.

  2. #2
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    Default

    You had me scratching my head there--in usual electronics parlance, SoC means "system on a chip".

    Of course, the MK14 is a semiautomatic assault rifle...

  3. #3

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    In recent years two or three people have been producing replica PCBs, but even built replicas often go for 200-300 due to the fact that all the parts take some finding and bringing together, once common parts like the 2111 RAMs and the 74S571 PROMs are very expensive to buy now. As to version, turn the machine over and look at the track side of the keypad - there will be an 'issue x' legend etched on the track side. Not surprisingly the best version to have is the final version, issue V.

    The original keyboards were terrible, so virtually the first thing anyone did was to discard them and attach a better homebrew keypad either onboard or offboard. That's why MK14s with intact working (that is, as much as they ever did) keypads are rare indeed.

    If you don't relish the tedium of typing code into the machine by hand, especially given that all your hard work vanishes when you pull the power, consider taking this approach:

    https://www.youtube.com/watch?v=-AXgyeH0F2E

    Details of that uploader project can be found in the forum thread mentioned in the text accompanying the video, and they were also posted hereabouts in this forum as well.

    PDF copies of the owners manuals describing the operation of the machine with the early and late versions of the OS respectively are here:-

    Early:

    http://www.8bity.cz/files/MK14/mk14ManualV1_OCR.pdf

    Late:

    http://www.8bity.cz/files/MK14/mk14ManualV2_OCR.pdf

    The website on which those files reside has a wealth of information about the MK14 generally

    http://www.8bity.cz/category/sinclair/mk14/

    There is also another old web resource for these machines:

    http://mymk14.co.uk/

    That should keep you going for a while.

  4. #4
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    Thank you for that very helpful post!

    Yes I've heard some uncomplimentary things about the MK14 keypad. Apparently it makes the ZX80 keyboard look like a Model M.

    I did read that there were some serious bugs with the original monitor. I don't anticipate using the thing a ton, so if it's an early issue I may just put the original monitor in place for 'originality' reasons.

    I'm wondering if anyone has artwork for the VDU board they offered? I might be game to build one and see what it's like working with it via CRT.

  5. #5

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    Quote Originally Posted by falter View Post
    I did read that there were some serious bugs with the original monitor. I don't anticipate using the thing a ton, so if it's an early issue I may just put the original monitor in place for 'originality' reasons.
    The original monitor was actually byte for byte the same as the 'SCMPKB' OS for the slightly earlier National Introkit (with added on keyboard and display). That is because the MK14 was directly derived from the Introkit, the kits were supplied to Science Of Cambridge by National Semiconductor.

    The revised / later monitor became available from Science of Cambridge part way through the production life of the machine. It was offered initially as an after sales upgrade to owners of early issue machines and eventually became the standard OS fitted to later issue machines, at which point the manual was revised. Since it was made / offered by Science of Cambridge and is not a third party product, it is as 'authentic' for it to be found in an early issue MK14 as it is for the original OS to be fitted. My issue II MK14 has had the 'New' OS fitted since about 1979. It is superior to the original OS in a number of ways:-

    -Takes far fewer keypresses to enter each byte of code.

    -Contains the support routines for the cassette interface, which I see your machine comes with. If you use the old OS, you will have to type some code into the machine before you can load or save code.

    -Contains support routines for the single-step feature, for which which your machine also appears to have the associated add-on support hardware.

    -Contains a built in jump displacement calculator, which the older OS did not.

    I notice your purchase does actually have its original keypad present and intact. The external keypad will be connected in parallel with it and the onboard keypad should still work, although possibly not very well ( That was normal, even in 1978 ).

  6. #6
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    What, A NASCOM 1 and now an MK14 ! Your British computer collection is expanding...

    >>> Yes I've heard some uncomplimentary things about the MK14 keypad.

    And that's putting it nicely! A friend of mine exchanged his keyboard for some large Post Office microswitches. They had a very nice feel to them and outlasted the MK14 in the end. They looked as ugly as sin though!

    >>> I did read that there were some serious bugs with the original monitor.

    No, not at all true. The monitor code could have been optimised and that made space for other things (as the next version of the monitor contained). That was all.

    >>> I'm wondering if anyone has artwork for the VDU board they offered?

    Martin (over at http://www.8bity.cz/2018/mk14-vdu-vi...-unit-replica/) has recreated the VDU. From what I read on his blog though, he doesn't have any PCBs left. Perhaps he just needs a few more people showing interest for him to do another run? He was also supplying the 'unobtanium parts' as a kit as well (e.g. the character generator). Not sure regarding his stocks of these components.

    From what I remember, it was a 'wire fest' to connect the VDU up to the MK14 itself - and required a crystal change (4.43 MHz to 4.00 MHz) and a few track cuts and/or pull-up resistors.

    I bought the MK14, VDU and cassette interface from him and I am very close to completing the build. Managed to find the calculator displays on e-bay for a quite reasonable price - but a Russian clone as opposed to the original part.

    Dave

  7. #7

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    it was a 'wire fest' to connect the VDU up to the MK14 itself - and required a crystal change (4.43 MHz to 4.00 MHz) and a few track cuts and/or pull-up resistors.
    True, and I wouldn't want to be doing mods like track cuts on a very valuable 40+ year old antique machine. Possibly the least intrusive / destructive way to connect a VDU to an original MK14 would be to solder a 40-pin turned pin socket to the pads of the CPU IC on the underside of the PCB and then use a wide ribbon cable with a 40-way DIP pin header mounted on the end to carry all the required bus signals back beyond the rear edge of the PCB.

  8. #8
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    Quote Originally Posted by daver2 View Post
    What, A NASCOM 1 and now an MK14 ! Your British computer collection is expanding...
    Not bad since prior to about 5 years ago I had no idea there *was* a British computer collection to be had, apart from the ZX81 doorstops! It's smallish but decent - I have a ZX80, ZX81, North American QL (minus power supply ), BBC Micro, Nascom-1 and now this. There's a couple I'd really love to get my hands on, like the PSI Comp 80. But the shipping from the UK is ?!#*@*#!(. That's why I pounced on this MK14, being already here in North America.


    >>> I did read that there were some serious bugs with the original monitor.

    No, not at all true. The monitor code could have been optimised and that made space for other things (as the next version of the monitor contained). That was all.
    Interesting. I forget which site I was on but they made it sound like you really, really wanted the so called '0000 00' monitor. It was all basically a lift of National's own monitor wasn't it?


    >>> I'm wondering if anyone has artwork for the VDU board they offered?

    Martin (over at http://www.8bity.cz/2018/mk14-vdu-vi...-unit-replica/) has recreated the VDU. From what I read on his blog though, he doesn't have any PCBs left. Perhaps he just needs a few more people showing interest for him to do another run? He was also supplying the 'unobtanium parts' as a kit as well (e.g. the character generator). Not sure regarding his stocks of these components.

    From what I remember, it was a 'wire fest' to connect the VDU up to the MK14 itself - and required a crystal change (4.43 MHz to 4.00 MHz) and a few track cuts and/or pull-up resistors.

    I bought the MK14, VDU and cassette interface from him and I am very close to completing the build. Managed to find the calculator displays on e-bay for a quite reasonable price - but a Russian clone as opposed to the original part.

    Dave
    Is it as I imagine it - like you power up, and you have a screen when you can enter your programs and such? Or is it more like the SWTPC where you have to write a program or driver first to 'engage' it, and then away you go?

    Let me know when you finish yours! Interested to see how it all works!

  9. #9

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    Quote Originally Posted by daver2 View Post
    Martin (over at http://www.8bity.cz/2018/mk14-vdu-vi...-unit-replica/) has recreated the VDU. From what I read on his blog though, he doesn't have any PCBs left.
    Wish I'd known about that sooner, I've got an original unbuilt MK14 VDU kit but after all this time I don't really want to actually build it and ruin the original PCB. I could have used the replica PCB with the original ICs.
    I bought it back in the late 90s sight unseen and assumed it was already built but was surprised to find it was still a kit. I nearly bought one when it was launched to go with my MK14 but ended up getting a ZX80 kit instead.
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  10. #10

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    Quote Originally Posted by falter View Post
    Is it as I imagine it - like you power up, and you have a screen when you can enter your programs and such?
    We wished!

    No, the VDU is simply a bit of hardware which reads 512 bytes of the machine's maximum possible 640 bytes and renders the contents as either graphics or characters. What that 512 bytes contains is entirely down to you / your code. If you're serious about attaching a VDU to it you really will need the missing 2 * 2111 'extra' RAMs to bring the machine up to a 'fully expanded' state.

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