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Re: [N8VEM-S100:809] S-100 Prototyping Board
I also have a few IMSAI's that are in need of
a reliable memory. Old memory cards with a high
chip count of obsolete, hard to find and a bit
expensive memory chips. Plus the possibility
of flaky sockets.
My plan is to build a simple 64k memory card with
minimal components using the buffered prototype
card. I would like the card to either start out
at 0000h or 2000h (for NorthStar DOS), ability
to do deposits from the front panel and maybe a
EPROM at the top end of memory.
I have a few ideas using some circuits from Andrew's
other boards and examples I've seen in some older
S100 books. Right now it's just on paper.
Would you be willing to share your design ?
----- Original Message -----
From: "Crusty OMO" <crus...@hotmail.com>
Sent: Saturday, May 12, 2012 10:10:41 PM GMT -06:00 Central America
Subject: [N8VEM-S100:809] S-100 Prototyping Board
A few months ago I bought the prototyping board from you. Naturally, you wanted to know how I would be using it. I can't blame you, since my curiousity is the same and I share the same love of electronics.
I bought an IMSAI back in November. I was thinking of using the prototype board for either remote controlling the IMSAI, or to simulate a floppy drive system using an SD card. But I am more interested in restoring this old IMSAI to using it's existing S-100 cards.
But those S-100 cards were driving me crazy. I needed some firm ground from which to trouble shoot. I was even starting to doubt my RAM cards, well, I even seen the DRAM cards do strange things when running with the Floppy Drive controller's BOOT ROM.
So, I used your card to create a 32K RAM + 32K EPROM card. This way, I can write some code and have a working system, then slowly introduce the other cards, etc. It's not very interesting, but it's proven to be quite helpful. I already located a weird problem with my SIO card that I never knew existed.
When I am finished restoring my IMSAI, I will repurpose the card as a stand alone operating system for another IMSAI located at the Personal Computer Museum in Brantford Ontario, Canada. I'll write up some demo code to flash the lights, or play some game on a dumb terminal.
This way, they can have their computer running. Without some software, the IMSAI might as well be a bunch of LED's wired to some Switches. ie not very interesting. I might even add more memory and find the way to bank switch, but I'm far from this goal to say for sure.
Cheers! and Thanks for a great head and help on my project machine.
PS. Feedback on the board. It would have been nice if there were traces that could "Almost" connect the Data IN and OUT busses. Almost being just eight short jumpers away (.1" per data line).