MSX Goa'uld board with Tang Nano 20k
MSX2+ engine in Z80 socket. It turns one MSX into an MSX2+ by replacing Z80 processor. FPGA in board contains:
- Z80
- V9958 with hdmi output
- MSX2+ BIOS
- 4MB mapper
- RTC
- PSG through hdmi
- OPLL through hdmi
- 2MB MegaRAM SCC+ through hdmi
Logic acts on bus control signals so that internal devices inside fpga take priority over external devices.
Warning
Current revisions 2, 4 are known to have a major flaw. Please, do not build these boards. See Errata.
Revision 2 uses SOIC-20 for 74HCT373 and 74LVC245 ICs, which are smaller:
Revision 4 uses TSSOP-20 ICs, to get an even smaller footprint:
- VCC for U5 75LVC245 is 5V which is out of specs according to the IC datasheet. See MSXgoauld_tn20k #15.
Mapper, MegaRAM can be relocated to slots 1, 2, or 3 using config menu.
- Replace U1, U2 -> 74HC373, U5 -> 74HC245
- Solder a 10K resistor array to data bus lines, pulled up to 5V
Goa'uld features a 2MB Super Mega RAM SCC+ by lfantoniosi. Most classical rom's will work with sofarun's default settings. Be sure to use sofarun 8.1 at least. Use utility GSMRAM.COM to load roms in the case sofarun doesn't work. It is possible to disable internal MegaRAM and use an external MegaRAM mapper. In this case, an SCC remains in Slot 0-2 to use with sofarun, using these settings:
Config menu is showed pressing g during MSX logo. New improved menu is created by nataliapc
- Enable Mapper: On by default. Disable when having compatibility issues or to use a different mapper
- Mapper Slot: 0 by default. Change to 1-3 to get mapper in a not expanded slot (best compatibility). Physical slot will be disabled
- Enable MegaRam: On by default. Same as mapper
- MegaRam Slot: 0 by default. Change to 1-3 to get megaram in a not expanded slot (best compatibility). Physical slot will be disabled
- Slot 1 Ghost SCC: Off by default. Enable to get sound from an SCC cartridge located in slot 1
- Enable Scanlines: On by default. Disable to get a clean hdmi picture
- Save & Exit: store new config and continue, changes in mapper/megaram settings will be effective after pressing reset
- Save & Reset: store new config and make software reset, changes will be immediate
Goa'uld has four internal slots available. As with other modules, internal slots take priority over physical ones. This means that when a device is using internal slot n, then physical slot n is disabled and any cartridge in that slot will not be detected. By default, BIOS, mapper, and MegaRAM occupy internal slot 0, leaving physical slots 1 to 3 available for cartridges. However, this default layout can cause compatibility issues with some software, such as tape games and large ROMs. To resolve these issues, you can move the mapper or MegaRAM from expanded slot 0 to one of the non-expanded internal slots (1, 2, or 3). This adjustment can solve many compatibility problems.
- Reset from config menu is not compatible with some hardware. Use physical reset button when possible
- Multimente: shows garbage characters. Move internal mapper to slots 1, 2 or 3
- Tape games fail: move internal mapper to slots 1, 2 or 3
- Big roms (>256 KB) fail: disable internal megaram
- Noises when loading a rom with sofarun: change sofarun settings to use mapper for that rom
Warning
Not yet fully working on all MSX!
- Get integrated circuits from trusted sources
- Use turned pins in header to avoid damages in Z80 socket
- Board is sensitive to dirty electrical contacts, way more than Z80. Keep cartridge & Z80 socket contacts clean
- When soldering headers, start with the inner one (Z80)
