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Thread: minimal F-11 SBC ?

  1. #1
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    Default minimal F-11 SBC ?

    In the past, I've hand-built a couple of boards using a T-11 with local RAM, EEPROM, and basic I/O.
    Now I'm thinking about doing the same thing with an F-11 chip.
    Has anyone done this before? Is it feasible to get the basic stuff down to just a handful of support chips?
    Is there enough published info to work out the details, other than just copying what's on a KDF11-A board? The KDF11 has a boat-load of stuff on it, but hopefully most of it is to support Qbus, memory management, and other stuff that I don't care about.

    Any comments welcome!
    Thanks,
    Pete

  2. #2
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    There have been minimal implementations with the J11, you might look at some of those. I've never looked at the bare CPUs in enough detail to know what'd be involved with the F11.

  3. #3
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    Quote Originally Posted by glitch View Post
    There have been minimal implementations with the J11, you might look at some of those. I've never looked at the bare CPUs in enough detail to know what'd be involved with the F11.
    Yes, thanks, I've seen one of those online. But I no longer have any J-11 chips to play with, but have a couple of F-11's.
    There's some fairly good detail in the KDF11-AA User Guide - it seems like a LOT of the logic would be in the "don't care about that" category, but it still could require a bunch of experimenting to make it go.

    Another thought I had: It might be useful to implement a bus device on a little card, and use a 40-pin DIP cable to plug into one of the empty sockets on a KDF11 board. That way, all the known-good support logic would still be there, but the Qbus would be inactive. The 'bus device' could be the console UART for starters.
    Which reminds me I should look at how the 11/24 CPU board works - I think it has 2 serial ports on-board with F-11 - perhaps they are directly connected, and not an actual Unibus device??

    Pete

  4. #4
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    I suggest that you get a DCJ11, currently on sale for 65USD. I have three sets of the F11 chips and there is quite some information but when I looked into it I found it is not enough to build your own system. I was always missing the subtle details in the documents I found. A standalone F11 CPU system would have no advantage over a T11 based system. Even more I think a T11 base system is perfect if you are going to build a PDP-11 without MMU. And why not start with a KDF11-A board? You could then start to build peripherals and memory cards.

    That said, I would again start with a DCJ11. This CPU has everything integrated and the support logic required is very minimal. Here is the Original PDP-11/Hack which also inspired my projects.

    Peter
    For more information about my projects see https://www.5volts.ch

  5. #5
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    Thanks for your comments Peter. Just last month, I sold two J-11 chips, and a KDJ11 board, on eBay. I don't think I will buy another one... .
    I will study the KDF11 and 11/24 boards a little more, and perhaps do some experiments.
    But of course, another T-11 project would be much more "practical". It's nice that it will run with 8-bit-wide memory, and only about 3 74LS chips required at a minimum. Here are a couple of pictures of a clock I made a few years ago. It is wire-wrapped, and the displays are from some old HP test equipment (after DEC, I eventually worked for Compaq, then HP). The time base is a 3.579545 Mhz crystal from a very early color TV (it looks likes a vacuum tube, at the top of the picture). Clock osc/divider is an MM5369. The T-11 runs a hack of FigForth V1.3.

    Pete
    T-11_clock.jpg
    t11_clk.jpg

  6. #6
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    And here's a pic of my other T-11 project from a few years ago.
    Pete
    assembled.jpg

  7. #7
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    I would say bad timing. The T11 however looks like a very flexible CPU and I doubt The F11 would be equally simple. So don‘t sell your T11s. I like your small T11 SBCs. Perhaps I should build a clock with one of my J11 chips.
    For more information about my projects see https://www.5volts.ch

  8. #8
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    I remember reading that DEC and WesternDigital worked together on the F-11 chipset - and it was the same as the MCP-1600???

    If this is true (and I can't confirm this - but a very quick random sample of a couple of instructions does give some credence to this statement) then some very useful documents can be found at http://www.bitsavers.org/pdf/westernDigital/MCP-1600/.

    Just remember that these documents appear to describe the macro instruction set in terms of HEXADECIMAL whilst DEC describe the macro instruction set in terms of OCTAL. That threw me for a few seconds...

    EDIT1: See https://en.wikichip.org/wiki/dec/lsi-11

    EDIT2: Page 17 of http://www.bitsavers.org/pdf/western...ssor_Oct74.pdf confirms this...

    Dave
    Last edited by daver2; February 21st, 2020 at 11:10 AM.

  9. #9
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    @ Daver2 - Thanks for the reference to the Soha & Pohlman paper - looks like the next step after the LD12. :>)

  10. #10
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    I thought the LSI was the MCP-1600 but the F11 was DECs own design?
    For more information about my projects see https://www.5volts.ch

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