| Pete Dashwood 2007-03-14, 9:55 pm |
|
"Charles Hottel" <chottel@earthlink.net> wrote in message
news:Xk0Kh.9919$PL.5496@newsread4.news.pas.earthlink.net...
>
> "Pete Dashwood" <dashwood@removethis.enternet.co.nz> wrote in message
> news:55rglcF25pi80U1@mid.individual.net...
> <snip>
> <snip>
>
> Ah that brings back memories. In college I programmed a PDP-8 in assembly
> language. IIRC it had pages of 200 octal words. Page zero could be
> accessed directly from any other page. Other pages could not be directly
> accessed. When coding and reaching a page boundary you had to do an
> indirect jump to the code on the next page. It had a single acumulator
> (register) which was also used for I/O.
>
> CLA - clear and add to the accumulator
> STA - store the accuulator
>
> It was the first computer I ever operated. There was a 3 x 5 card pasted
> on the front with some octal numbers. You used switches to load the
> numbers into memory. This was the bootstrap loader. We used that to read
> the main loader in via paper tape. The main loader loaded another paper
> tape with the linker, assembler, and editor which we used via an ASR-33
> teletype to created our programs. We punched them to paper tape and
> loaded them for testing . There was a single step mode that served as a
> debugging environment. Ah the good old days.
>
Do you know why it was called PDP?
The following may be "urban myth" but it was relayed to me in the early '70s
by someone who worked at the NZ importers for DEC.
Around that time (and a bit earlier... I think it started with the PDP6 in
the early/mid '60s) the US government (who felt, with some justification)
that the USA led the world in computer technology, were very concerned about
the evil communist menace getting their hands on this new technology.
There were very rigid rules about exporting computers to communist bloc
countries and paperwork and duty on exports to friendly nations were also
formidable.
However, all these problems went away if the computer wasn't a computer.
DEC therefore designated their system as a "Programmable Digital Processor"
(not a "computer").
It worked, and the company experienced a world-wide boom in export sales.
The PDP8 was a 12 bit word machine so I'm not sure where the "8" came from.
In fact all of the designated numbers are a mystery to me. Perhaps someone
reading this can shed some light on it?
Pete.
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