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Xenon 2: Megablast
Z80 Source Code in ROM
The ROM image contains bits of Z80 source code in ASCII format. It is presumed that the assembler used to create the final build didn't clear out unused memory and thus the sources are left over from the assembling phase or from a text editor.
ROM Mapping
Each Xenon 2 ROM is 256KB in size and uses mapping in slot 2. That is, the first 32KB of the ROM is always mapped into Z80 address space at $0000 - $7fff [1]. The remainder of the ROM is composed of 14 banks, each 16KB in size. These banks are mapped, one at a time, into Z80 address space at $8000 - $bfff.
The game's code is divided between the first 32KB of the ROM and at least the first & tenth 16KB banks.
ROM Version Differences
The only differences between the Image Works and Virgin Games versions of Xenon 2 are within the ROM header and the data for the publisher's logo screen.
In the ROM header, the two ROMs have different product codes (IW: 27012, VG: 27038) and different version numbers (IW: 0, VG: 1).
The publisher screen is completely different between the two versions:
- The Image Works ROM contains (compressed) tile data for this screen at $3c000-$3d45a. The Virgin Games ROM requires less data, in part because it uses fewer tiles (IW: 314, V: 300): it contains tile data at $3c000-$3d160 and the end of the Image Works data remains, unused, at $3d161-$3d45a.
- The two versions have very different palettes for the publisher screen (located at $0295c-$0296b) and name table data ($3d45b-$3da5a).
- The Virgin Games ROM uses a larger timeout when displaying the publisher screen, showing it for almost four times as long as the Image Works ROM.
- ^ All address ranges on this page are inclusive.
Researched by Bock, Paul Baker
- See the main page for Xenon 2: Megablast
