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Semi-OT - What all the Logo blathering is leading up to...

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So here's what I really had in mind when I first started bringing up the 
terrapin talk a couple weeks ago...

A friend of mine and I are designing a little pocket computer based on a 
65C02 (I had the idea, he took it and ran with it; he's designing it at 
the hardware level, but the firmware is mainly going to come from me).  We 
were talking about how to handle the video mode, and since he and I had 
already developed one of the two working emulators for the Nabu, we wound 
up deciding to just clone the Nabu's graphics chip, since we both had a 
fair idea how the thing worked.

Guess what... that makes it pretty similar to a very specific 
configuration of an Apple ][!  Specifically, an Apple ][ with a sprite 
card.  That means I can do some theoretical code testing while I don't 
have a workable simulation of the system, using existing resources, such 
as MAME.

So...

I had in mind to try to pack as much as I could into the ROM space, which 
would be somewhat larger than that of the ][ (would be 32K, actually, and 
unbanked).  And I was thinking, at first, the usual - you know, the kind 
of stuff we have on the ][ line - monitor, miniassembler, BASIC, and we 
started to think about what else might be viable, and Logo had been tossed 
around as an idea.  That's why I was trying to figure out how to implement 
turtle graphics - because ultimately I was going to have to implement 
turtle graphics on a TMS9918/65C02 pairing.

That's also going to lead to another question...  Waitaminute, the TMS9918 
doesn't have anything like the ]['s split screen graphics mode!  Actually, 
that can be fudged, with a slight limitation.  G2 mode basically splits 
the screen into three 256x64 windows, each implemented as a 32x8 set of 
tiles.  32*8 = 256 - so often a person will just write 0-255 into each 
set, then dink the font to create an all-pixels-addressable mode.  In this 
case, that would only be done for the first 2 blocks, then 128-255 in the 
top half of the third, and a standard ASCII font loaded as 0-127 of the 
third tile set.  You lose the ability to do inverse text (there's still 
ways to do this, by dinking the color memory), but that's still plenty 
enough if you need graphics and text together.  You get 256x160 graphics, 
plus 32x4 text.

So testing will probably be done initially on an emulated ][ - and that 
will be enough to make sure the _logic_ works.

Ultimately, I was wanting to create an environment as similar as possible 
to an Apple //e, within the limits of the hardware I was targetting - and 
have it, you know, a monitor, mini-assembler, BASIC and Logo - and Logo 
could avail itself of the BASIC in order to implement some of its 
features, they could shere their floating point library and their graphics 
support (which in Logo's case would be used to implement turtle graphics).

Once I brought in graphics and Logo, though, that's where my brain melted. 
(I'll probably need to do preliminary implementations in some other 
language and then translate it into 65C02 postfacto, but I know nothing of 
low-level handling of graphics like Bresenham algorithm, circle 
algorithms, etc., and might need a hand on these things.)

The Logo implementation, if it should come to fruition, would also be 
ported to the Apple since there would be practically no further effort 
required.

-uso.

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Thread

Semi-OT - What all the Logo blathering is leading up to... Steve Nickolas <usotsuki@buric.co> - 2024-02-25 07:09 -0500
  Re: Semi-OT - What all the Logo blathering is leading up to... fadden <fadden@fadden.com> - 2024-02-26 08:30 -0800
  Re: Semi-OT - What all the Logo blathering is leading up to... Steve Nickolas <usotsuki@buric.co> - 2024-02-28 12:23 -0500
    Re: Semi-OT - What all the Logo blathering is leading up to... Steve Nickolas <usotsuki@buric.co> - 2024-02-28 12:27 -0500

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