Software - ROM Cartridges

Character Set ROMs

Kayde Electronic Systems and dk'tronics both produced a 4K Graphics ROM supplied on a small PCB that plug internally into the ZX81's ROM socket. Both Graphic ROMs provided the ZX81 with 7 alternate character sets, and their PCBs even allowed them to be fitted with RAM to support 4 user defined character sets. The 4K Graphics ROMs were almost identical, differing only with regard to one of the character sets. This page present 16K ROM cartridges consisting of the edition 2 ZX81 ROM followed by either the dk'tronics or Kayde 4K Graphics ROM. User defined character sets are not supported by the ROM cartridges (such functionality can be achieved using the onboard 8K RAM facility instead).


dk'tronics Graphics ROM character set 1   dk'tronics Graphics ROM character set 2   dk'tronics Graphics ROM character set 3   dk'tronics Graphics ROM character set 4
Kayde / dk'tronics character set 1
(USR 11904)
Kayde / dk'tronics character set 2
(USR 11909)
Kayde / dk'tronics character set 3
(USR 11914)
Kayde / dk'tronics character set 4
(USR 11919)
dk'tronics Graphics ROM character set 5   Kayde Graphics ROM character set 5   dk'tronics Graphics ROM character set 6   dk'tronics Graphics ROM character set 7
dk'tronics character set 5
(USR 11924)
Kayde character set 5
(USR 11924)
Kayde / dk'tronics character set 6
(USR 11929)
Kayde / dk'tronics character set 7
(USR 11934)

The standard Sinclair character set could be reselected on both Graphics ROM by executing USR 11939. The user definable character sets could be selected using USR 11944, USR 11949, USR 11954 and USR 11959, and although these routines exist in the ROM cartridges they will not yield sensible character set pixel patterns.

Kayde and dk'tronics released a range of software that utilised their respective Graphics ROM:

dk'tronics titles:

Kayde titles:

  • Centipede
  • Peckman
  • Space Invaders

Downloads

Both the Kayde and the dk'tronics ROM cartridges contain a slightly modified version of the ZX81 edition 2 ROM. This is to ensure they can be used on all ZX81s, including one containing the Sinclair hardware fix to overcome the infamous floating point bug present in the first edition ROM. Alternate versions of each ROM cartridge are available that have the LOAD and SAVE routines patched to support RS232. This functionality is identical to that described for the ZX81 RS232 ROM cartridge except that transfer routines are not included.

Click here to download the dk'tronics Graphics ROM cartridge [V1.03]. 16K
Click here to download the dk'tronics Graphics (with RS232 support) ROM cartridge [V1.03]. 16K
Click here to download the Kayde Graphics ROM cartridge [V1.03]. 16K
Click here to download the Kayde Graphics (with RS232 support) ROM cartridge [V1.03]. 16K
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