MSX 64k games ROM program

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By ARTRAG

Enlighted (6455)

ARTRAG's picture

21-11-2020, 16:58

There are plenty of reasons to produce 64Kb roms without mapper. They are cheaper and easier to assemble and provided you use the c000h bank as storage,e.g. for VRAM data or for data to be relocated in RAM, they are also quite simple to program.

By mjnman

Supporter (8)

mjnman's picture

21-11-2020, 22:53

Thanks for the answers. I would like to put some 64k and 48k rom games in the EPROM 27C512 but doesn't seem like too easy for my knowledge

By ARTRAG

Enlighted (6455)

ARTRAG's picture

21-11-2020, 23:55

This is the code for Uridium 64KB, maybe it could help
https://github.com/artrag/Uridium-msx1

By sd_snatcher

Prophet (3367)

sd_snatcher's picture

22-11-2020, 01:22

But remember that there are no 64KB EEPROMs or Flash chips that can be written with just +5V. This means that cartridges can only be made with 27C512 EPROMs. As a result, if a bug has to be fixed after the game was released, anyone who purchased cartridges won't be able to update them without some painful desoldering/resoldering. If the cartridge is still on its warranty, things might get complicated.

This means that using a MegaROM has an additional advantage: cheap flash or EEPROM chips that can be easily updated if necessary

Corollary: Cartridge makers don't have to waste time slowly erasing EPROMs with dangerous UV lamps.

As ridiculous as it may sound, a 27C512 is more expensive than a 29EE010 chip these days.

By santiontanon

Paragon (1105)

santiontanon's picture

22-11-2020, 03:14

I don't know what is cheaper or more expensive hardware-wise, but Star from the MATRA shop always keeps reminding me that his cartridges are 64KB, and I should use it all (when I only want to use 32kb or 48kb haha)

By gdx

Prophet (3833)

gdx's picture

22-11-2020, 03:16

W27C512 x10 cost about $5 on ebay and no need UV to erase them and it's fast.

https://www.ebay.com/itm/10PCS-W27C512-45Z-W27C512-27C512-EE...

By cons to reprogram them, you have to either desolder them or make an adapter.

Making Rom cartridge with mapper is a bit more expensive but it is less limited to use.

About flashroms, the cheap keep their data for about 20 years only, sometimes less if it is recycled components.

By sd_snatcher

Prophet (3367)

sd_snatcher's picture

22-11-2020, 14:00

The W27C512 is indeed a nice alternative for the 27C512. I've some in my stock and use them to replace maskROMs and UV EPROMs that have gone bad.

But, personally, I wouldn't recommend them for new products. It's an obsolete part that's not made anymore, and it's much better to left the remaining ones exactly to replace other DIP ROMs on old equipment without the need of adapters.

Otherwise, the same problem that happened with the AT29C256 will happen to the W27C512: people began using the DIP AT29C256 like crazy for new projects, and now they're pretty much extinct. All you can find are fakes and defective chips being sold at high prices.

The 29EE010, OTOH, is still in production. This means that not only you can buy them from reliable sources, but they're going to last longer and are not going to go extinct so soon.

By Danjovic

Master (157)

Danjovic's picture

24-11-2020, 13:00

Just a quick question. Would the MSXDOS2 cartridge
mapping schene work with 64k games?

By ducasp

Champion (386)

ducasp's picture

24-11-2020, 15:00

Danjovic wrote:

Just a quick question. Would the MSXDOS2 cartridge
mapping schene work with 64k games?

Yeah, there are games using it, it is known as ASCII 16K Mapper...

By Danjovic

Master (157)

Danjovic's picture

24-11-2020, 22:26

Thanks!

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