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    6502 branch at page boundaries

    Hi I read the spec for how the relative branch works but still don't get the fine details of exactly what it does. If the instruction branches forward or backwards when close to a page boundary. Say the instruction has the branch instruction at xFE which way does it go for a positive or...
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    KIM AIM SYM eprom programmer card

    I've posted a picture on the post: Is there a SYM-1 PCB or good picture? of a programmer card that I believe is to be used with the generic KIM/AIM/SYM computer. I was hoping someone might have some information on the use?? Thanks Dwight
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    Hal computer systems

    A friend has 2 Hal computer systems looking for a new home. One is a Beta machine and the other is a regular production. Both have been in storage for three years but both were running when put away. These are pickup in the lower silicon valley area. For those that may not remember such things...
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    The Swiss army knife

    I just got this note from Jameco. Digilent-Analog-Discovery-2 It looks like it is what we all want. Check it out. It looks to good to be true. Of course you'd need a few extra things like an input attenuator, some BNC connectors and some probe. Also, some connectors for logic probes. I wonder...
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    Someone save this one Quick!!!

    https://www.ebay.com/itm/General-Automation-1972-SPH-45-16-Minicomputer-Console/323932770200?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 Dwight
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    A useful 68000 deveopment machine

    I was looking at the earlier post on the development system with key pad and LED display. Although, these machines are fun to fiddle with and clearly collectable. If I were doing anything serious with a 68000 I'd want an assembler and disk drive. When I look at this, I realize that I already...
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    The bell tolls.

    https://techcrunch.com/2019/06/07/make-magazine-maker-media-layoffs/ It is like the loss of a close friend. Days and times will be different now. Dwight
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    PB-10 programmer schematics

    Hi I see the post about someone trying to find information for the programmer they have. It is a shame that there isn't more information for these devices. I've had to repair my Needham PB-10 once. I realize that manufactures like to keep their schematics private but the Needham PB-10 is now...
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    Poly88 is now running

    I've been bring my old Poly88 back to life. I'm making slow progress but mostly going slow. The keyboard I have has an interesting modification. I'm not sure why it was there. It had a switch on the side that connected two of the data out pins together of the KR2376. The funny thing is it didn't...
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    Using embedded micros for emulation/replacement of various I/O of classic computers

    Going Forth from the C of compile/load/debug cycles. Say you want to run a PDP11 from your iPhone or what ever. The ESP32 with WIFI can be a fun way to deal with such things. At the Maker Faire, Dr. Ting will run a workshop using the ESP32. It is not specific to classic computers but with a...
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    CMOS staic RAM board

    I have a RAM board with 64K of 6116s. It has not manufacture label. The switches are labeled. There are some for extended addressing above A15, These I understand. It has another set of switches labeled: E000 E800 F000 F800 EXT ADR HALF PHANT PHANT I assume EXT ADR enables extended addressing...
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    replacing all the capacitors

    Hi I see this over and over. "I think I need to replace all the capacitors in my machine because it isn't working". Ok, how many times has one replaced the capacitors and got a working machine when done? A single shorted capacitor is relatively easy to spot but replacing them all, I question...
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    For those that don't get updates from the CHM

    Hi I thought this would be of interest to all. https://www.computerhistory.org/atchm/madeleine-moment-connects-moore-s-law-artifacts/ Dwight
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    Need help with a switching power supply?

    Hi For many, switchers are magic. I stumbled on this Russian fellow and he does a great job explaining switcher supplies. https://www.youtube.com/watch?v=cX4q0e124C4 In one of the videos, he shows some tricks in trouble shooting these fussy things. I've only seen a few of his videos but they...
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    Intel 4004 code

    Hi I suspect most will not have any idea but there are a number of new people on the list so I thought I might ask while I'm thinking of it. When the 4004 first came out they made a development called the SIM4-01, SIM4-02, and SIM4-03. The -02 and -03 were functionally the same but the -03 used...
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    PS/2 keyboard to 5V parallel keyboard

    On another thread, I'd said that I'd create some code for the Blue Pill ( a STM32F103 on a small board that cost about $3 on ebay or others ). I've mostly finished it. Although, one can buy a kit for around $15 and I believe a finished unit for around $20, this is much cheaper. One only needs 10...
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    Working on my PS2 to Parallel keyboard, I need a little ARM help.

    I've got the STMF103 code working well but now I'm trying to document. I wrote some hand generated assembly code but lost my notes ( scribbled on a piece of paper that likely made it to the recycle bin ). I have two instructions that I'm not sure what they are. I was hoping someone might be able...
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    PS/2 to parallel keyboard project

    I'd earlier stated that it would not be too big a deal to convert the output of a PS/2 keyboard to a parallel for older computers, now that keyboards were getting rare. It turns out that it is not as simple as I'd thought going in. Making a PS/2 to XT looks to be relatively trivial. I've put...
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    what to do at end of life

    Here in California, we are required to have a CO detector in our house by law. These run for about 7 to 10 years, depending on the manufacture and then they are programmed to quit. They give out a message on the LCD as End of Life or some such and start making annoying beeps. Just curious, I...
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    Please save these Polymorphic machines

    These are in Dallas Texas. If someone doesn't pick them up they'll be recycled. There are several 8813s, 8810s and one poly88 ( no cover ). He had documentation as well, some keyboards and monitors. These are rare machines. I have system88 software for the 8813/8810s. I also have cassette images...
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