HJS22
HISTORY
I
was at the age of 16 all ready infected with the computer bug.
My school received in 1971 two old mechanical IBM computers:
a IBM 402 and an IBM 5?? calculator.
Unfortunately the school didn't get a puncher (IBM 029) with
it and the 402 can only print numerics (IBM 402 is the numeric
only version of the alpha/num IBM 420). The fun was quickly gone.
My next school was better equipt: it had a IBM 1401 (with 4kbyte
!), an 1402 cardreader, 1403 printer and two 729 tape units.
On this machine I had my first computer programming experience:
AUTOCODER. (this was real fun !)
This 1401 machine was given by IBM and delivered with some IBM
System/360 model 50 Field Engineering documentation.
I have no idea why, but these manuals gave me for the first time good
inside knowledge of micro-programming.
In 1975 I decided that I wanted my own computer. So I
started looking around but nothing was available. This was the
era of the
M6800 and the i8080 micro-processors. I called an local electronics
supplier
for the price of an i8080 chip, at that time the bare CPU chip
was priced at Nfl 1200,- (USD 500,-).
This was too much for a college kid like me, so I decided to built my
own computer with TTL logic.
The machine architecture was more or less copied from the M6800. It was
micro programmed with 256 words of 40 bits each.
After several design changes and a lot of debugging it was
finished round 1979. Below is a polariod picture taken
when is was
(more or less) finished.
From the top downlwards:
- Power utility unit and mains keyswitch
- 16kByte core memory (ex IBM 1800)
- CPU
- I/O unit
- 8 Bit papertape reader (boot device)
In 1981 I met my wife and all my HJS22 computer activities where then
stalled.
"HJS22"
is a combination of my initials followed with my age when I
build the system. Initially I named the system HJS21, but
renamed it later to HJS22.
