Feature request - Z80 emulation

Discuss the new Altair 8800 Micro

Feature request - Z80 emulation

Postby Kevin Adams » Jun Tue 25, 2013 9:04 pm

I suspect this is a tall order....

Back in the day I believe it was common as CP/M evolved to swap out the 8080 card for a Z80 CPU card.

The little Altair 8800micro would have a much increased software library available to it if it emulated the Z80.

Is this possible? difficult?


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Re: Feature request - Z80 emulation

Postby garryj » Jun Thu 27, 2013 4:16 pm

I wouldn't say impossible, but it would almost certainly require a ground-up re-coding. Although the Z80 is (mostly) binary compatible with the 8080A, they are very different CPUs under the hood. Given the resources available with the 16Mhz. ATMega 8515 MCU used by the 8800micro, IMO it would be a struggle to develop a Z80 emulator that performed well.
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Re: Feature request - Z80 emulation

Postby vbriel » Jun Fri 28, 2013 10:43 pm

Yes, Garry is correct, ground up would be required and probably a new micro controller. The system was originally designed with the goal of Altair BASIC. Z80 CPU's can not run Altair BASIC as there is a slight difference in the half carry flag. This is enough to bork BASIC on start up.

It would be possible to do a Z80 machine with a real Z80 since they are much easier to interface and don't require multiple voltages a nice choice. My original idea involved the Z80 until I found out about the half carry flag issue the hard way. However, a project like this is too close to the Altair micro and therefore not contrasting enough. I'm in the middle of another project now in my spare time so I don't think I could get to something like this.
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