MZ-80A / MZ-80K extra RAM

S_U_C
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Re: MZ-80A / MZ-80K extra RAM

Post by S_U_C » Sat Sep 28, 2019 2:15 pm

If you want faster video ram access you can always modify the hardware to use the HBL instead of the VBL you get 25 HBL / 1 VBL.
On the MZ80K this effected the keyboard input routine and you got about 20 characters per keyboard press not very helpful.

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Re: MZ-80A / MZ-80K extra RAM

Post by mz-80a » Sun Sep 29, 2019 2:25 pm

Jo Even wrote:
Fri Sep 27, 2019 8:32 am
Ahh... That's a bit diappointing, I've always believed that the 700 had hardware scrolling. Not that much use in the extra VRAM then.
There is use in the extra VRAM. I use the second page in conjunction with an interrupt to swap between VRAM pages on my 80A to create new (non Sharp) graphic characters and special fx.
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Re: MZ-80A / MZ-80K extra RAM

Post by Jo Even » Mon Sep 30, 2019 9:38 am

mz-80a wrote:
Sun Sep 29, 2019 2:25 pm
I use the second page in conjunction with an interrupt to swap between VRAM pages
How do you swap VRAM pages?

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Re: MZ-80A / MZ-80K extra RAM

Post by hlide » Mon Sep 30, 2019 11:15 am

It is just for MZ-80 A which has the hardware scrolling so the swapping is just a matter of setting the page address every line at most. Scrolling hardware is done by accessing the address between $E200-$E2FF (one byte is 8-character unit, so the next line is 40/8 further, that is $E200+5*N where N is the line (between 0 and 50).

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Re: MZ-80A / MZ-80K extra RAM

Post by mz-80a » Mon Sep 30, 2019 11:16 am

Jo Even wrote:
Mon Sep 30, 2019 9:38 am
mz-80a wrote:
Sun Sep 29, 2019 2:25 pm
I use the second page in conjunction with an interrupt to swap between VRAM pages
How do you swap VRAM pages?
https://mz-80a.com/programming/elementary-tricks-tips/

"Double Buffer Horizontal Split"

:)
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Re: MZ-80A / MZ-80K extra RAM

Post by mz-80a » Mon Sep 30, 2019 11:18 am

Although that isn't the interrupt part but shows how to swap between pages of VRAM. Is this actually not available on the MZ-700 ?!
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Re: MZ-80A / MZ-80K extra RAM

Post by hlide » Mon Sep 30, 2019 11:25 am

Nope, again MZ-700 is not retrocompatible with MZ-80 A but with MZ-80 K. There is no successor to MZ-80 A.

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Re: MZ-80A / MZ-80K extra RAM

Post by hlide » Mon Sep 30, 2019 11:27 am

And while I may be attempted to add that missing feature which seems inherited from MZ-80 B (yeah MZ-80 A nd B share the same video circuit at some point), I'm not sure it may be easy to do so with an hardware add-on without butchering the mother-board.

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Re: MZ-80A / MZ-80K extra RAM

Post by hlide » Mon Sep 30, 2019 11:32 am

Here is the retrocompatibility chain in my opinion:

Code: Select all

MZ-80K ___ MZ-80C ____ MZ-1200
                   \__ MZ-80A
                    \_ MZ-700 ___ MZ-1500
                               \_ MZ-800 

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Re: MZ-80A / MZ-80K extra RAM

Post by mz-80a » Mon Sep 30, 2019 1:25 pm

Thanks, that's a good diagram! It'd be nice to expand that into the other MZs. Because, for instance, I don't really understand what the MZ-2200 is, and some of the others.
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