Re: BASIC4 in a static RAM PET?

From: Nicolas Welte; address is valid for replies (Re:) only! (
Date: 2002-09-02 17:50:43

William Levak wrote:
> I don't know how your device works so I acn't say for sure, but there are
> several differences.

i posted a link to the device's info page some days ago. It's a little board
that plugs into the 6502 socket and it has its own onboard 32kB RAM and 128kB
ROM. Also the memory decoding is done on the board, so I don't have to depend
on the capabilities of the host machine. In the PET, I mapped RAM to
$0000-$7fff and ROM from $9000-$ffff, with a hole for I/O at $e800-$efff. 

> On the original system board, the A000-AFFF bank is not enabled.

BASIC4 uses the b000 bank, the orginal boar also doesn't have a socket for
this one.

> There are circuit differences that put a lot of snow on the screen with
> Basic 4.0 in the original system board.

Ah, that's the video problem you mention in the readme file! I could live with
that, and I think it could be fixed rather easily by adding a wait routine for
the v-blank, as it's present in the old 1.0 and 2.0 ROMs. Sounds like 4.0 has
the "speed-POKE" built in already.

I still wonder why the non-CRTC editor ROMs don't work in VICE as well, if I
specify a non-CRTC 2001-8 machine. 


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