Sinclair ZX80 / ZX81 / Z88 Forums

Greetings SirMorris, Just catching up on all the wonderful ZedEx developments including your versatile mmc interface. The hires problem you mentioned is most likely caused by the 251 decoder which should be enabled with MREQ OR RFSH to guarantee RAM CS set up time for reading hires pixel data during...

While it is possible to use a ZIF socket to swap in various system 8K ROMs, it would seem simpler to use a large capacty EPROM, Flash and/or NVRAM containing multiple operating systems and select the active partition using software or a selecor switch. In addition, such chips can store many other us...

The 8300 ROM was not compatible with MC programs that used ZX81 ROM subroutines. In addition the expansion connector is missing some signals (busreq, busack?) The 8300 video subsystem is also different using a separate character ROM in the ULA and makes it incompatible with hires software. You can't...

Pleased to meet you Doctor. Can you tell us more about the add-ons you have designed?

Wilf

check out this article on the subject:

http://www.user.dccnet.com/wrigter/inde ... khires.htm

cheers

wilf

Have a peek at the ZX97 ROM in the EightyOne emulator. I hacked the ZX81 ROM to expand the 8K ZX BASIC ROM to up to 16K with the additonal ROM area between $A000 to $BFFF. Only a small part of this additional ROM space was used to expand ZX81 BASIC syntax routine and to customize ZX81 BASIC with 10 ...

There are several versions of the WRX video driver including one that runs on a 1K ZX81. The WRX16 HRG program displays 256x192 pixels using two "display files" : 1) the dummy display file is a short program which is executed while displaying each horizontal line of 256 video pixels. It is called ab...

Fred Nachbaur wrote a good fast tape loader called F-Load which he bundled with his SCRAM BASIC program. Anyone have a copy of that floating around?

wilf

Hi Mike,

First adjust DF-SZ with POKE 16418,0 or else 24 SCROLLs would leave the two command lines of the LOWER screen still fully expanded.

wilf

The collapse DFILE ASM program I posted does not clear the BASIC variables. try this example: crunch_DFILE.tzx (btw how can I save a .p file?) Your first post seemed to indicate that you want to collapse an expanded DFILE of a 1K BASIC program, developed in a 16K environment, so that when this 1K pr...