6502 oddities from the past..

[BillO]

Found this in the January 1980 Byte magazine:

That MINIMAX II would be about $23K today!!!

Didi you ever use one of these?

Bring out your 6502 oddities and curiosities..

[6502inside]

This might have been its disk drive. "The Minimax II is also known as the ACT Series 800."

https://www.computinghistory.org.uk/det ... k%20Drive/

And here's the ACT Series 800. Looks very similar.

https://nosher.net/archives/computers/p ... uthink_act

[jds]

I recently found out that the Panasonic HHC is 6502 based. Maybe not an oddity, but quite interesting.

[BigEd]

(Panasonic HHC featured 10 years ago in our weekly posts!)

[barnacle]

I do like a nice tidy DIP board

Neil

[Erstwhile]

jds wrote:

I recently found out that the Panasonic HHC is 6502 based. Maybe not an oddity, but quite interesting.

Hhc.jpg

We got one of those with printer and some expansion (ROM) modules for Life Insurance calculations.
It was given to us 20 some years ago as a joke wedding gift!

[josgrp]

In the description for the Computhink Minimax I found this text.

If the full set of 6502 opcodes is insufficient, it is possible to microprogram a further 64 instructions using the opcodes whose two low order bits are turned on, ie those whose LSBs are 3,7,B or F. The advance publicity literature suggests that a good use for this facility would be to perform Pascal. In case that is not enough, a wealth of ROM based routines are available for use by the assembler programmer.

Does anyone know how you can microprogram a 6502?

[GARTHWILSON]

Welcome, josgrp.

josgrp wrote:

In the description for the Computhink Minimax I found this text.

If the full set of 6502 opcodes is insufficient, it is possible to microprogram a further 64 instructions using the opcodes whose two low order bits are turned on, ie those whose LSBs are 3,7,B or F. The advance publicity literature suggests that a good use for this facility would be to perform Pascal. In case that is not enough, a wealth of ROM based routines are available for use by the assembler programmer.

Does anyone know how you can microprogram a 6502?

The 6502 does not use microcode.  However, see our own Jeff Laughton's KimKlone 65c02 with pointer-arithmetic-friendly extended address space and 9-cycle ITC Forth NEXT.  It gives 6 new registers and 44 new instructions.  Note that this is not just a proposal, but actual working hardware.  See pictures in this forum post and on the next page of the forum topic.  He's kind of a genius at this kind of thing, and also has ways to form I/O instructions that do a lot in each instruction.

Also, the CMOS version (ie, 65c02) adds new instructions and addressing modes, and many other improvements.  See my article on it at http://wilsonminesco.com/NMOS-CMOSdif/ .

The 65816 takes it further, and its op code table is full.  The '816 is not just a 6502 with potentially wider registers.  It has lots of improvements that make it able to do things the '02 simply cannot.  See my article about common misunderstandings about the '816, at http://wilsonminesco.com/816myths/ .

[BigEd]

While the 6502 is indeed not microprogrammed, I can imagine some opcode extension scheme which is. But I've not seen any implementation detail as to what the Minimax did (or was intended to do, in the case that this opcode extension business didn't ship.)