I finally got a hold of an IMSAI 8080 like the one used in the "War Games". Now this is going to be a fun computer to play with. Lots of blinking lights and switches.
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I purchased this Matt Millman's 2708 programmer shield (unpopulated) for the Arduino Mega 2560 R3. This allows me to program 2708 chips, something I cannot do with any other programmer I own. It will actually program 2704 / 2708 / TMS2716 / MCM68764 and MCM68766 EPROMs. The only one it will not program is the 1702 / 1702A. However, Matt has a board for that too. Unfortunately, that board is nearly made entirely of surface made components, so it would be tricky to put together.
As you can see, the EPROM I am programming here is for my Ithaca Audio Floppy Disk Controller. The Commodore US*1M is a follow-on calculator to the Commodore US*1 (their entry-level calculator), with a basic accumulating memory register functionality. The US*1M was introduced in the latter part of 1973. The calculator I have used a planar gas-discharge display, and a set of Western Digital ER1422B and ER1432B calculator chips with date codes in 1973.
Finally got all the components for this IA-2020 Floppy Drive Controller board. Now all I need to do is program a 2708 EPROM with the appropriate code. I am currently looking for a BIN or HEX file of the Ithaca Audio FDC-II (IA-2020) code. It would fit on a 2708 EPROM.
Making an adapter for my Optimal Technology EP-2A 2708 programmer, so I can attempt to program some 2708's using an Arduino UNO. If this works, this could lead to a very simple Arduino shield for the UNO to program 2708's since the EP-2A uses only 3 ICs which are still readily available.
What I done so far is use a 44-pin cable connector and wired it up to a small PCB which in turn connects signals to an Arduino proto-shield via a ribbon cable. The PCB also will connect to the various voltages needed (not yet wired up). The ribbon connector on the Arduino proto-shield will be connected to 12 of the Digital pins available on the UNO (8-for data and 4 for control). Interestingly enough, the EP-2A does not need address information. It auto advances the address based on a clock signal (one of the 4 control signals) sent from the computer (or in this case the Arduino). I wanted to test my Solid State Music IO-4 card to make sure it is working correctly (to eliminate it as a source of problems with another computer I am working on), so I decided to see if it would work with the JAIR. I pulled all the jumpers from JP10 (per Josh's instruction manual, all I/O mapped is to S-100 bus). I set my IO-4 board to: Serial A 0x20 Data Port 0x21 Status Port 9600 baud, N,8,1 It seems to partially work. The boot loader text displays fine, but then the computer seams to struggle and start to output junk. It never prints the dots or starts to load the SD contents. I have attached a photo of the screen. If I revert back to the onboard SIO all is fine again. Not sure why the SSM IO-4 card would cause the JAIR to hang like that. Any ideas? Mind you I did not play with the parallel port settings, however if I understand it correctly, with the jumper J10 empty of jumpers, the onboard parallel port is disabled as well, correct?
FYI - If you come across 16-pin ICs labeled as 151555700, then grab them. They are actually 2102 SRAM. I have two 8k cards full of them. There is no way in hades that I would have known that if I came across these sold as unknown.
Today I made my own pin straighteners for 0.30 inch wide ICs and 0.60 inch wide ICs. This works a lot better than just bending the pins on the edge of a table. The chips are run on guides through a pair of bearings which force the pins vertical. MiniTerm Associates ROM/EPROM board
Looking for some documentation on this ROM/EPROM board from MiniTerm Associates. I want to know how to set the jumpers, if I use a different set of EPROMs. µUN Jello RAM board Does anyone have any information on this µUN Jello RAM board. Even some images of a completed board might help as it would let me know component values if the resolution is high enough. Please e-mail me at v a 3 n g c @ g m a i l . c o m if you can help. (remove spaces in email name) I am happy to say, I have my JAIR S-100 single board computer up and running. I have had this board sitting around for awhile but only finished building the power supply recently. This baby emulates the Altair and IMSAI computers. In fact it will work with their front panels and other cards as well. I'm going to use it to test out some S-100 cards I have. I really like this little computer.
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AuthorCharles Baetsen holds a Bachelor and a Master's degree in Engineering Physics from McMaster University in Hamilton, Canada. Archives
February 2024
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