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KIM-1 60K Memory Board

5K of memory was fun, but there is a lot of code out there that resides at $2000 and won’t fit in less than 8K, so the next logical step was a larger board.  This is not a product yet, but the first pass experimental board seems to be working well.  It provides RAM from $0400 to $13FF (4K) and then from $2000 to $FFF7 (56K) for a total of 60K.  The KIM monitor runs as it always did, and all interrupt vectors still branch through the existing KIM monitor code.

No, the 128K RAM chip is not vintage, but the other three chips were definitely around in the 1970s.  Replace the RAM chip with banks of 2114 and the rest of the logic would still work.

Here it is in the static test jig, sometimes called Kimulator or Kim-Sim:

K60K_1And here it is tied into the KIM-1 while a non-stop memory test has been running for a couple days now without a single problem:

K60K_2The ribbon cable plugs into the I/O board.  In case you wondered what that 10 pin connector was for, this is it.

So when will this be real?  I need to run a couple more experiments to add one more feature, then it’s time to order another set of boards.


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S-100 System (a major distraction)

So back “in the day” when I was first getting started in computers, S-100 machines were awesome displays of power and sophistication (and money).  They were well out of my teenage allowance reach, while a KIM-1 was affordable.  My goal was to eventually build an S-100 machine and get CP/M installed.  It took nearly 35 years, but finally did:

S_100_1Okay, so it’s got some modern stuff like an IDE board, but it’s still S-100 and is definitely running CP/M 🙂


It’s maybe 20 pounds, sucks a lot of power (notice the huge power supply on the right hand side of the chassis) and probably has less memory/processing power than the wireless keyboard on my iMac.

But’s it’s S-100 running CP/M, so it’s definitely got the cool factor going for it.