Signetics 8x300 instruction set

From: Peter C. Wallace <>
Date: Fri Dec 3 09:49:20 2004

On Fri, 3 Dec 2004, Tom Jennings wrote:

> I've been trying to recall, with no success, how subroutine
> calls were implemented in the 8x300. I used to write code for
> this weird thing (realtime video processing) and the assembler
> I used (some horror that ran under TSO) hid it from me so I
> don't have a clear recollection of the method.
> It's a really weird CPU, "subroutines" were essentially jumps,
> as in a lot of machines, but the "return" was through some
> strange jump table or something.
> Once upon a time there was a website with CPU instruction cards
> (man I had a huge pile of these things, pitched loooong ago...)
> but I can't find it. Nothing on bitsavers I can find.
If its the same as the SMS300, My old Osborn introduction to microcomputers

"The SMS300 has no subroutine or interrupt handling logic" ... "subroutine
logic can be created with an XEQ instruction and an appropriate jump table,
but this is rather clumsy, in most cases it would be simpler to do without

Isnt the 8X300 a predecessor to the PIC somehow?

> (There's also some really bad info out there on the origins
> of "Harvard" architecture, attributed to some stupid hardvard
> vs. princeton microprocessor design thing. Please -- about 40
> years earlier: that asshole Aiken. No one liked him anyways.)

Peter Wallace
Received on Fri Dec 03 2004 - 09:49:20 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:36:37 BST