I bet your z80 didn't do this...

[InTheSand]

Ooh!

Very cool! Been a while since I've done any Z80 assembly language stuff, but this looks like a fantastic project!!!

 - Ali

[InTheSand]

JimS wrote:
That does look like a fun project...
Back in the Elder Days, i.e. before the Z80 was retro, I built a homebrew Z80 computer.

Ah, well hello from another former "homebrewer"! I have two Z80-based home systems, one cannibalised from an ancient multi-user CP/M system and the other based on the innards of a 3.5" RS232-interfaced floppy drive (briefly on the market in the UK in the 1990s).

However, both my systems are serial port based, e.g. no bitmapped graphics (though one has an AY-3-8912 beeper for sound!), so a project like that one would be very interesting to me...

Come to think of it though, assuming the MiniMig goes ahead and that its FPGA is reprogrammable in the final version, I guess there's no reason why other computer cores (ZX Spectrum, C64, etc) couldn't be developed to run on it? Or is there a reason why this wouldn't be possible?

 - Ali

P.S. @Karlos: nice pic! :-)

[InTheSand]

And not forgetting the Commodore 128 - which had a 6502 and Z80 inside, also allowing "dual booting" into C64-mode, C128-mode and CP/M...

EDIT: I guess that should read "triple booting"!  :-)

Did many (any?) C128 users ever run CP/M on their machines?

 - Ali

[InTheSand]

Interesting to know!

And you're right about the 8080 - all original CP/M versions were designed to run on that and don't use the additional features the Z80 provides...

 - Ali

P.S. I'm glad Zilog changed the assembly language opcodes when the Z80 was produced... 8080 assembler is just plain nasty! Familiar-ish, but just... wrong....!!!

[InTheSand]

Sounds like your homebrew project was a good one! Nice to have a real display rather than slow and boring RS232 terminals or emulators to display any output!

I created the rudimentary parts of a basic OS for my machines - usual BIOS/BDOS-type functionality, plus a command interpreter with monitor-like functions (dump/fill areas of RAM, show/change registers, upload code, etc) but haven't done anything with it for years.

As for MiniMig cores... If the 68K can be shunted out of the way, the FPGA core itself is probably more than capable of emulating an entire basic 8-bitter like the Spectrum... Or perhaps the 68000 could be used to run the Z80 code with the FPGA emulating the rest of the hardware? I guess there'd then be synchronisation issues though... But I'm sure someone will have a go!

 - Ali

[InTheSand]

Yeah, bloomin' clone rubbish!!!  :-)

 - Ali

[InTheSand]

The eZ80 does look like a nice CPU to base a project on... As Karlos says though, time is always a problem!

If this project goes anywhere, I'd be very interested in getting one if they ever became available for sale... A 40MHz 1Mb Speccy-ish machine sounds fun!!!

@kvasir - yes, the original Gameboy and the colour version use Z80 derivatives but they're not 100% compatible due to some differences in the instruction set.

 - Ali

[InTheSand]

@rzookol: no, hadn't seen that, thanks for the info! Looks interesting, but I guess the Spectrum doesn't meet the hardware requirements due to its colour attribute layout...

Another Z80-related project is SpeccyBob, which builds a Spectrum clone out of common parts (mostly 74xxx).

 - Ali

[InTheSand]

Ooh! I want one!

Seems a very good deal at US$250...

Might have to see what the bank balance is like once all the Christmas stuff is out of the way!

 - Ali

[InTheSand]

There's no reason why ye olde 8-bitters can't continue to be used for stuff that doesn't require much in the way of CPU grunt. Nice to know you have some still in action!

 - Ali