Summary

Magnetic card reader/writter B7400

Card description

Keyboard technology ca 1974

I have no more keyboard of this old time. (thrown in dustbin just few years ago)
Key technology.

ECC

Error correction in dynamic RAM designs. (1981-1982)
This technic gave the ability to use bad chips or to correct the famous problem due to alpha particules
found in ceramic packages. Ceramics were not enough pure and contained active nuclear components
giving alpha particules, adestroying some precious bits in memories...

Chips 8409 de NS (ca 1982, 16+6 bits)

Eprom emulator ca 1978

Eprom emulator gave the ability to debug programs without the need of erasing the eprom memory each
time a bit have to be modified
Note: Some chips have been removed or repaired. Ah latch-up!

Emulator view (simple port here)

How to make a 64kB memory (ca 1979)

To have 64 KB of memory, it was necessary to wrap 128 chips. It was a very hard job! (4096 wires)
I used at this time some kind of skycrapper. It was necessary to be able to change a chip to repair memory.
So I used chip holders. (It was not so simple!)
Here you can see 2 kinds of memories (1979-1980)
One with 2114 chips and another one with 6514 (to have data retention when powered off)
Chips are 1kx4 (cmos for 6514)
Before chips were soldered each upon others, ... but to repair, no solution!

Ram stacks (ca 1980)

Note: To use 128 chips of memory, you need to have special buffer due to the high capacitance
of the bus (640 pF + wiring) I used 8T97 (Ad) et 8T26/28 (data)

Created manually

Org 2007-11-12, Translation

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depuis le 28jan2008