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I finally got around to building up a Glitch Works reproduction SSM-IO2 as a serial I/O. It's a straightforward build based on the board manual's schematics. I added an MC1488 and MC1489 to handle the EIA interface as somewhat more period correct parts (similar to the Processor Tech 3P+S). The...

I recently had Altair BASIC VER 1.0 loading from paper tape on an IMSAI 8080. The binary came from Mike Douglas' DeRamp.com site. (Details at https://ef1j.org/wiki/index.php?n=Main.Version1). Here's a shot of the cold start routine messages: My question is: Does anyone know if a copy of...

I'm currently working on a Polymorphic BP/5 motherboard as part of some bowenfusenwerk caused by a shorted tantalum on a card I was testing. After powering the machine back up, something in the power supply let out a burst of magic smoke. Can anyone post a picture of their Poly-88 backplane...

Nothing says "S-100" quite like memory problems, which seem to crop up unexpectedly and lead to mysterious faults and crashes. My latest escapade has involved DDT suddenly not running on a 63K CP/M 1.4. I think I've narrowed it down to an 8K board addressed at C000-DFFF. I'm running a bunch of...

Anyone know the correct cpmtools diskdef parameters for single density North Star MDC-A1? I'm using the Lifeboat CP/M images from deramp.com on a Sol-20. I guessed this one, but it doesn't quite work: # Northstar Micro-Disk System MDS-A1 diskdef ns seclen 256 blocksize 1024 tracks...

The behavior of my Sol-20 differs from that documented in the manual - presumably a mistake in the latter. The differences are in the parity bit settings and the total word length setting. The manual states that S4-2 and -3 should be OFF and ON for 7-bit operation. I confirmed that it is the...

I've been working on a North Star MDS system for my Sol-20. I have the MDC-A1 controller and the rebadged Shugart SA-400 in the "North Star MICRO-DISK Cabinet (MDS-CAB)". My drive was set up with the power regulator option to take unregulated +9V and +18V, usually from the power rails of the...

I had to share a hard-won victory getting this Sol-20 up and running. I'll post repair notes to my site soon. It involved a few iterations of power supply, PC board, and keyboard troubleshooting. Next up is refurbishing the keyboard, a topic of much discussion on the board. I'm planning to...

I have a Seals 32KS, a 32K static RAM board. Searching for information or ads on this board has not yielded much. The 8KS SRAM board manual is available online, but I've only found scant references in the old journals to the 32KS, mostly in quarter page ads of mail-order retailers. I'm guessing...

Running CP/M 1.4 (2-15-78 ) using the Tarbell single density controller BIOS, I've had persistent PIP failures when copying files from drive A: to B:. Most of the time the first sector's worth of data of the copied file is E0 or 00. The rest looks ok. I'm guessing that this means it's...

I've recently brought up a Thinker Toys SSSD Disk Jockey floppy controller with two "Discus" drives (Shugart 800's) on my IMSAI 8080. I cobbled together a cbios.hex and cboot.hex based on the Disk Jockey manual, with modifications to set the baud rate on the serial port from the default value in...

I've been puttering around with the Tarbell CP/M BIOS listings from deramp and the Maslin archives. One BIOS says "CVE IO4 48K CPM V1.4 of 7-20-79/9-5-81". What does CVE IO4 refer to? What is the significance of the 9-5-81 date? Another puzzle for me is where exactly the skew 6 interleave is...

...any four digit number starting with a "7" catches your eye. ...you have a collection of burned up RIFA caps. ...one of the unexpected and sublime benefits of the internet becomes having access to all of the microcomputer books and publications you couldn't find / afford / understand in the...

I've been having problems with a high current 78H05K regulator (the 5A, TO-3 version of the 7805) on an S-100 memory card. Took a gamble and bought three spares from Taiwan via ebay. They finally arrived, but after soldering one in, it failed immediately. It went into thermal shutdown. It never...

I recently had an N8T380N "Quad Bus Receiver" go bad on an S-100 card. I found a few spares on eBay, but I was wondering if there is a replacement I missed that would be available from Mouser / Jameco / Digikey / etc?

Anyone have the manual for the VG Z-80 Rev 1 CPU board? I can only locate the Version 2-A PDFs in the usual places.

According to the IMSAI "pre-history" on IMSAI.net [1], the first IMSAI 8080 kits shipped on December 16, 1975. [1] http://www.imsai.net/history/imsai_history/imsai_pre_history.htm

Many a period writeup as well as the official Osborne product literature refer to the "Universal terminal emulation" of the OCC Executive. Was this a vaporware feature that was never rolled out? (My understanding is that it was supposed to be a feature due to the inclusion of a Z80A-SIO chip in...

I was wondering if anyone out there was an Osborne-1 owner when they came out in the early 80's. I'm curious what the early owner / user experience was like with these machines and upgrades. I have two early S/N OCC's (a tan case 1 and the harder shell 1A) that have had multiple upgrades...

I'm looking for documentation on the COMM-PAC modem -- pictures of the modem and physical dimensions, as well as any technical information (a pic of the board itself would be great.) I have reviewed the documentation from bitsavers, but as far as I can tell, no drawings or schematics are...