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/Vintage/Sinclair/Software/ZX Spectrum Software/Interface 2 Cartridges/ZX81 Emulator (Paul Farrow)/ |
| k1.spdns.de / Vintage / Sinclair / Software / ZX Spectrum Software / Interface 2 Cartridges / ZX81 Emulator (Paul Farrow) / |
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/Vintage/Sinclair/Software/ZX Spectrum Software/Interface 2 Cartridges/ZX81 Emulator (Paul Farrow)/ |
| k1.spdns.de / Vintage / Sinclair / Software / ZX Spectrum Software / Interface 2 Cartridges / ZX81 Emulator (Paul Farrow) / |
Paul Farrows, www.fruitcake.plus.com, has written some modified roms for the Sinclair Interface 2, ZX Spectrum and ZX Spectrum+ 128K and later 128K computers to emulate the ZX81 and ZX80. His page on these roms is very detailed and i will only summarize it in short here. If you are interested in using these cartridge for more than just testing and loading a ZX81 game, then you should visit his site.
These roms make a Specci run as a ZX81 at a very high degree of compatibility. Even lots of high-res games work! You can choose from 4 memory setups, Screen, keyboard, printer and load/save routines are patched to work with the Specci hardware. Also the slow and fast mode is simulated. In fast mode the screen is blackened, and the interrupt routine does not draw the TV display, making the ZX81 running at full speed.
The screen update must be emulated, because the ZX81 has a completely different, character-based b&w only screen display. Because the ZX81 uses Ram at address $4000 for the display file, the Specci display cannot be located at this address too, because then you would see the bytes poked into the ZX81 display file on the Specci screen 'as is'. Instead the possibility of the 128k Speccies to use a display file at $C000 is used. With every interrupt the display file of the ZX81 at $4000 is examined and a corresponding image at $C000 is drawn. Because the memory from $C000 upward is used for the ZX Spectrum's display file, Paul Farrow's Roms cannot emulate a ZX81 expanded to full 48k ram.
Below are the Roms. There are 5 versions to be used with an Interface 2 attached to a 128k Specci. They incorporate a modified ZX81 rom, just the i/o routines are redirected to the new routines and the interrupt routine now includes Paul Farrow's screen update routine.
The 5 different versions are:
Older versions of Paul Farrow's roms are in the old version folders and include some roms to be used with a modified 48K ZX Spectrum or to replace a 128K Specci's internal rom.
Paul Farrow has also written some utilities to transfer a file to the emulated ZX80 or ZX81, which work on Windows (i believe). Load, Save and Print on the ZX81 can either directly work with the Specci's Tape and Printer routines or they can be redirected to ZX Interface 1 RS232, the 128K's AUX or the 128K's Keypad port. To receive or send the data on a PC you can use his "ZX File Transfer Utility" from below. Serial data uses 8N2 bits at 9600 baud. The printer output is suitable for a Epson-compatible dot matrix printer. For further details visit Paul Farrow's site.
The "CartridgeGenerator" is originally intended to create IF2 Roms for the ZX Spectrum, but can be used as well to create ZX80 and ZX81 game cartridges. On how to build a IF2 cartridge see his site or on my site at Doityourself/IF2 cartridges.
Finally, "P81 to P Converter" is an utility to remove the name from a .p81 file to make it a .p file, a plain data dump, which can be downloaded to a ZX80 or ZX81 using the File Transfer utility on a PC and the file transfer menu on the ZX80 or ZX81.
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