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Recent content by intabits

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    New version of the "B7094" emulator system for IBM 709x and 704x mainframes from the early 1960's

    There is a new release of the "B7094" IBM 7094 emulator at https://github.com/Bertoid1311/B7094 . This new version, as well as fixing some long-standing bugs in the user interface, has updated demos to include an alternate IBSYS ("KSYS61"), whose FORTRAN II processor can do chaining and run...
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    Hi Jim, I've been sending the occasional email in the hope of making contact with you, then I...

    Hi Jim, I've been sending the occasional email in the hope of making contact with you, then I thought of this. Sometimes I get an undelivered message, so I know you didn't hear me, but usually no error, but because of no reply, it seems you still don't receive them... Let me know if you see...
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    Any precautions required or advice before powering up a model 80?

    Thanks for the replies. So I won't just apply power and hope for the best. I'll open it up and clean it out, looking for any visible issues. And test the PSU separately, probably with a dummy load as Al suggests. Then watch closely for problems when it's all back together. I believe this...
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    Any precautions required or advice before powering up a model 80?

    I have an 8580 that hasn't seen a volt in maybe 25 years. I'd like to power it on soon, and wonder if there are any pitfalls to avoid. If it were an old valve radio, I'd use a variac, and a dim bulb current limiter, but probably not correct procedure fro a switching PS. Any advice that you...
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    H740 Power Supply, what's your Q1?

    H740's in my gear:- PDP8/F: MJ2500 PDP11/05: TIP645
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    My first Omnibus interface - Progress so far

    I've done a bit more on this, but want to take a break and play with other toys, so for anyone interested, this is the project so far. Schematic, PCB files, firmware, software is in the attached zip. This is NOT a finished & polished project. The documentation above is for interest only. But...
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    My first Omnibus interface - Progress so far

    This is my first Omnibus interface card, using the flip-chip adapter boards shown in this thread:- https://www.vcfed.org/forum/forum/genres/dec/1228572-a-general-purpose-flip-chip-adapter-board-worth-doing It's a mash-up of the boot-loader designs by Malcolm Macleod and Roland Huisman, plus...
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    A general purpose Flip Chip adapter board - Worth doing?

    Here is my first attempt at a home-made Omnibus interface card using these adapters. It's a mash-up of the boot-loader designs by Malcolm Macleod and Roland Huisman, plus some extra stuff (power supply voltage monitoring, and provision to read the memory address and memory data buses) Yes, I...
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    A general purpose Flip Chip adapter board - Worth doing?

    A couple of weeks ago, I had some of these adapters made by JLCPCB. As suggested by Roland, I didn't bother with the ENIG Gold fingers (and it would have near doubled the price). The boards are too short for the fab to do the beveling, so that must be done manually on some sandpaper. For...
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    A general purpose Flip Chip adapter board - Worth doing?

    Good to hear that non-rectangular boards don't cost much more. I've only ever ordered rectangular boards, so I was worried that it might significantly add to the cost. I've also never ordered boards with edge connectors, or gold plating, so I'm also concerned about specifying all that correctly...
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    A general purpose Flip Chip adapter board - Worth doing?

    There's a bunch of projects out there for "after market" and DIY boards for DEC machines, targeted at Unibus, Omnibus, Qbus, and possibly others. These projects include: extender cards, prototyping cards, Unibone, QBone, MOS memory boards, Boostrap card emulators, etc. What they all have in...
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    Video: M8650 working on PDP-8/F

    For anyone who might interested, a video where I get my PDP-8/f to do some I/O at last. Using the M8650 board for serial communications (but only at 110 baud). https://www.youtube.com/watch?v=qa1jhO37umw
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    M8650 annotated schematic, with highlighted Omnibus and Berg connector pins

    The annotated schematic for the M8650 at:- http://tronola.com/M8650_schematic_annotated.GIF is a pretty clear copy of the schematic, and the annotations look useful. But the external connections to the board are all over the place in the original DEC schematic, and the annotations did not...
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    List of PDP-8 Omnibus signals

    I've updated my Omnibus Signals List, fixing some errors, and adding three new fields. Two of these fields refer to information contained in Chapter 9 of the "Small Computer Handbook 1973" The new fields are:- * A 2 digit "Load Driver" that indicates the Load and Driver types, as per those shown...
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    Videos: Testing DEC H740 PSUs and PDP-8/f power on & simple tests

    Thanks for that. H7450-Mod-1 I've added the missing circuitry, trying to abide by the existing layout, and with DEC's. But VCFED won't let me upload RAR or ASC. Where can I put them? H7450-Mod-1B My idea of how it should be drawn. Notes: (Designators below are as used in...
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