Re: Subing EZ80 microcontrollers for Z80A cpus

Thanks Clay... and Bill.

For now; I’ll table this plan... Too busy with the Xy Gen and other projects anyway.
I did spent about two nights thinking and planning; I think it’s possible to do the substitution – I’m just not sure if it’ll have the desired impact.

This biggest problem is the EZ80 seems to have removed the !refresh pin... so that would have to be duplicated somehow. I’m also concerned about possible uC peripherals conflicting with Sega’s memory (or IO) map.

As Bill mentioned; the PCB would have to have a 3.3V regulator... and the EZ80 doesn’t come in a package I really like. BGA or 144pin LQFP... both may be on the big side for a DIP sized drop in.

I wouldn’t really care about “loosing” 90% of the EZ80’s functionality; as long as it “improved” the lag problem.
I know Z80s are widely available as pulls / etc; I just wanted to get a pipelined version to see what it did to the lag.

A side effect; might be that highscores could be saved in flash; but still a complex project I’m not motivated to tackle yet.

Too bad I have a day job. ;P
John

From: Clay Cowgill
Sent: Saturday, December 03, 2011 4:18 AM
To: vectorlist@vectorlist.org
Subject: RE: VECTOR: Subing EZ80 microcontrollers for Z80A cpus
Just to clarify, I *think* the Z80's /INT is coming from the vector generator boards, but at a fixed rate. (40Hz sticks in my head, but that could be wrong.) ...and I think the game timing is set by the /INT rate, so changing the Z80's instruction rate shouldn't affect the draw time or game speed *unless* the Z80's is dropping frame rate (ie, not completing it's main loop before the next video refresh is due). The 'coprocessor' nature of the VG made it possible to single-step the Z80 and whatnot during development and maintain an image on screen though.

I also could be completely full of crap (or at least mis-remembering). (To put this in perspective, when I was messing with the G80 system I sussed out how the vector generator stuff worked using a Fluke 9010A and got basic drawing routines working in Al Kossow's simulator that ran on the Mac-- which in turn eventually trickled down in to MAME. So it "has been a while". ;-)

-Clay
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Received on Sun Dec 4 04:26:24 2011