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IMSAI Series Two

Posted by Hemos on from the get-your-legacy-on dept.

Dino writes "You can actually pre-order a new IMSAI here. These folks bought the rights to produce the IMSAI in the late seventies, and provided the unit used in Wargames. It has a genuine S100 bus, but also has modern features as well, the most interesting being a driver that will allow you to access an ATX motherboard via the parallel port as a disk drive."

2 of 260 comments (clear)

  1. I got started on the original IMSAI... by superscalar · · Score: 4, Interesting

    My uncle had built the thing from a kit, and then we inheritted it. We didn't quite have to key in binary code on the front panel (although it was a good exercise), but I DO remember being excited about getting a used 32K S-100 memory card up at the Trenton Computer Festival (do they still have those?). We started off with a cassette interface and a 64x16 character monochrome display. Eventually added two 'hard-sector' 5-1/4 inch floppies (about 100K each). The processor got upgraded from the original 8080 to an 8085 and later a Z-80. We also built a TMS9918A-based video card (that was a pretty neet chip - wasn't it used in the Colecovision or something?) and I later built a MIDI interface for it. This was all back in the early/mid-eighties. A BSEE, MSEE, and 15 years of experience later, I still learned a lot of what I use on a regular basis on that machine.

    1. Re:I got started on the original IMSAI... by lhand · · Score: 4, Interesting

      I paid about $300 for my IMSAI when I first bought it. It was all the money I had so it took months before I could buy a memory board for it and actually do something with it (like blink the lights).

      The mother board has 22 slots. That meant I had to solder 2,200 connections for the sockets. Whew! Of course there was none of that surface mount stuff so it really wasn't so hard, just tedious.

      When I had another $500 I bought a floppy drive and controler board. The 8 inch single-side double-density drive held a whopping 300K of storage. The Jade controller I built had a 4 MHz Z80 chip on it. The Main CPU was a 2MHz 8080A. It seemed weird to have a better processor on the disk controller than as the main CPU.

      I had to build a custom clock circuit to run a serial port at 55 baud so I could interface to my old Teletype model 20 (Baudot machine). But man, it felt great to key in some instructions and watch a big piece of hardware start hammering away and shake the table it was on. I wrote drivers to convert ASCIIBaudot so I could actually use the TTY as a terminal.

      God, I miss that. I wish I had room to set up that old thing. Not sure what I'd do with it, but I really loved it.

      For those of you who don't know what good this type of thing can be: it provided a machine which was completely understandable, required understanding to build and use, and therefore provided training on how every little bit of a computer worked. That training wasn't available in school unless you went to someplace like MIT or Cal Tech. The only computer classes available at my college at that time (1973) were a few Cobol classes in the Business school.

      In a very real sense, we were all kernel hackers then. And yes, it was fun.