This cartridge works on the following PCBs and with the following models of Spectrum:

Latest Version: 1.05
PROM Size: 8K
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This 8K ROM cartridge is designed for use with the Spectrum 16K, 48K, +, 128 and the grey Spectrum +2. It performs a test on the ROMs within the machine to identify whether they are corrupt. It also checks for the presence of the ZX Interface 1 and reports on which edition is it and whether it is corrupt.

The cartridge first determines whether it is running on a 16K, 48K or 128K machine, and therefore how many ROMs require checking. It then computes a 16-bit addition checksum and an 8-bit exclusive-or checksum for each ROM, and displays these in hexadecimal. It then compares them to the known list of Spectrum ROM checksums and displays the model if identified. The known ROMs are:

ROMs other than those listed will need to have their checksums compared manually. The addition checksum is created by ADDing together all bytes from the ROM. The exclusive-or checksum is created by XORing together all bytes from the ROM.

The cartridge then checks whether an Interface 1 is connected. It does this by attempting to invoke the Interface 1 paging mechanism by executing an instruction within the ROM cartridge located at $0008. If an Interface 1 is connected then it will attempt to page in its ROM, even though the ROM cartridge will over-ride it in the memory map. The ROM cartridge then runs a routine copied to RAM that pages the ROM cartridge out, computes the checksum of the first 8K of the ROM area, and then pages the ROM cartridge back in. The Interface 1 ROM is then paged out by executing an instruction within the ROM cartridge located at address $0700.

Spectrum ROM Tester 128K Spectrum Screenshot Spectrum ROM Tester 48K Spectrum Screenshot

There were two editions of the Interface 1 ROM released, both of which this ROM cartridge can identify. The edition 2 ROM was fitted in Interface 1 units with serial numbers greater than 87315. A third edition of the Interface 1 ROM was rumoured to have been produced but not released. Therefore, if the ROM cartridge cannot identify the edition of the Interface 1 ROM yet all functions of the ROM operate correctly when used from BASIC, it maybe that it is fitted with the third edition ROM. Please contact me with any such occurrences so that the nature of the ROM can be investigated.


Click here to download the Spectrum ROM Tester ROM cartridge. 8K