4-in-1 multicart: Difference between revisions
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+------ select mirroring (0=H, 1=V) | +------ select mirroring (0=H, 1=V) | ||
==Quirks== | ==Quirks== | ||
* Multicart register overlaps CNROM register and multicart register is not protected from writes after game is selected, so all games CHR-bank switching rougines had to be patched. | * Multicart register overlaps CNROM register and multicart register is not protected from writes after game is selected, so all games CHR-bank switching rougines had to be patched. | ||
* The register is not initialized on startup so reset vector of all games had to be patched | * The register is not initialized on startup so reset vector of all games had to be patched | ||
* DIP28 1 MB mask roms are used both for PRG and CHR (pin 22, which is normally used as !OE in DIP28 EEPROMS is utilized as A16) | * DIP28 1 MB mask roms are used both for PRG and CHR (pin 22, which is normally used as !OE in DIP28 EEPROMS is utilized as A16) | ||
Revision as of 12:50, 13 August 2017
4-in-1 multicart
This cartridge contains 4 CNROM games:
- Puzzle
- F-15 City War
- Volley Ball
- PokeBlock
CPU banks
$8000-$ffff: 32 kB ROM bank (swapppable)
PPU banks
$0000-$1fff: 8 kB ROM bank (swappable)
Mirroring
H/V (selected by software)
Subject to bus conflicts
Yes
Registers
$8000-$ffff: PRG/CHR bank selection register
7 0 -------- xxPPCCCC |||||| ||++++- select 8kB CHR-ROM bank at $0000-$1fff ++----- select 32 kB PRG-ROM bank at $8000-$ffff +------ select mirroring (0=H, 1=V)
Quirks
- Multicart register overlaps CNROM register and multicart register is not protected from writes after game is selected, so all games CHR-bank switching rougines had to be patched.
- The register is not initialized on startup so reset vector of all games had to be patched
- DIP28 1 MB mask roms are used both for PRG and CHR (pin 22, which is normally used as !OE in DIP28 EEPROMS is utilized as A16)
