Sunday, 18 February 2018

cbm 710/720 hires board found!

I just found this Hires-Graphics-Extension in a B720. It plugs between the Char ROM and the Screen Memory. It also plugs in the 74245 buffer U30 - and the 245 is on the hires-board. It has 32kB dedicated ram. That's enough for one page with 640x350 resolution monochrom. It also has some wires to the userport and an addition 7414 piggypacked...

Has anybody Infos about this extension?

Friday, 9 February 2018

PET2001 Basic1 IEEE-patch from Vice

I want to use my 2031 floppy with my blue PET and Basic1 ;)
So I extracted the basic1-patch from Vice xpet and checked the differences to the original roms.
I found some patched bytes in the F000-F7FF area (H4 ROM).
Now I burned the patched rom in a 2816 and plugged it in my PET (2316 board).
A 2716/2816 works as x000-x7fff rom because both cs-pins are used low-active.

Sadly that doesn't worked. Andre Fachat (he wrote the patch for vice) wrote me that there is also some code at EF00 - I ignored this area because normally a PET has no rom in this IO-area.

I shortened some IO-error-messages in the F000-F100 area, placed the patch-routines from EF00 there between the messages and changed the addresses of these routines.

Now I'm able to load and save at floppy drive!

You will never get a "file not found error" - the PET writes everytime loading & ready - but doesn't load, if no file found! - without any error message - I don't know why...?

The new error messages are:

TMF = too many files
OPEN = file open
FNF = file not found
DEVNP = device not present
NIF = no input file
NOF = no output file

Friday, 2 February 2018

Adapting Kosmon to 2001 original ROMs

I'm desperately searching for a monitor with A/D for the PET 2001 with the first original roms.
Now I got the source for Kosmon from Olaf Seibert.
Kosmon is for C64 and PET with basic 2/4 and 40/80 columns.

Sadly nearmost all addresses in the original roms are totally different, because of the zero-page-basic-input-buffer!
I have to change a lot of zeropage addresses and kernal-jumps to the original roms.

After the first debugging round it's running (with more bugs):

Working: R, X, M, D
But there are still some bugs to find...

...and I should throw out the floppy part, because it doesn't work with original roms and saves RAM!

Thursday, 1 February 2018

PET2001 Machine Language Monitor

Today I typed the original Commodore machine language monitor for the 2001 with the first ROMs.
It was originally sold as tape.
...and it was listed in the first release of the US-manual.

It runs also in VICE with the basic1 patch:

Here is the PRG-file: PETMLM.PRG