ma-20 clone (msx2 cartridge)

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By l_oliveira

Hero (526)

l_oliveira's picture

29-03-2016, 17:36

It's being worked on and will be a complete product. Not a DIY frankenstein.

By NYYRIKKI

Enlighted (5382)

NYYRIKKI's picture

29-03-2016, 19:29

l_oliveira wrote:

It's being worked on and will be a complete product. Not a DIY frankenstein.

Well I'm fine with it... That would have been useful feature to only maybe 1% of users anyway, so... actually we went straight back to the question of what kind of users should be supported. Smile

By l_oliveira

Hero (526)

l_oliveira's picture

29-03-2016, 19:34

I'd say the main userbase of it would be people who just want to play MSX2 megaroms or use MSX DOS2 and disk based Japanese games.

By Grauw

Ascended (8442)

Grauw's picture

29-03-2016, 20:26

l_oliveira wrote:

On a sidenote, I tried to convince European programmers to follow the proper programming rule once (here) and people said they would never do something like that because "this" or "that" (that lame argument about performance and complexity).

One of my reasons were that this type of cartridge was extremely uncommon.

Now I’m considering to support it. It’s going to depend on the structure of my code, whether I’ll be able to easily adjust the addresses with some self-modifying code in a few select places. I’ll see if I can arrange it so that this is the case.

Btw I’m also interested in a cartridge like this. Bonus points for a superimposition input? If not too expensive.

l_oliveira wrote:

If you connect a new VDP to the existing (0x98) port without disabling the existing device, there will be a I/O conflict and neither will work properly. That's why. If there were any way of putting the internal VDP into some sort of "silent mode" (there isn't, all you can do is stop it from rendering video) writes intended to the MSX2 VDP would wake it up.

What about a mode mirroring only the writes on ports 98H-9BH? Might increase compatibility by a few games and software applications which don’t read the status registers, and rely on the BIOS interrupts.

By NYYRIKKI

Enlighted (5382)

NYYRIKKI's picture

29-03-2016, 20:11

l_oliveira wrote:

I'd say the main userbase of it would be people who just want to play MSX2 megaroms or use MSX DOS2 and disk based Japanese games.

I expect that you are very much right... It is just that there is no perfect solution and if you want to get past the limitations either you can make the computer to be like other MSX2 machines or you can do plug'n play solution & solve the issues with compatibility with software.

In perfect world all software would already be compatible, but in reality there are hundreds or thousands of titles that would require a patch. Too big effort even if all the current hobby coders out there would jump into it as a project. As I said, I agree that 99% would like to take the later option, but if making it possible to select also the 1st option would be just as easy as writing the VDP-routine in correct way for a game then it is just as valid question to ask why not to enable that? (<> support that) This way only one fix would be needed by the user and he has possibility to select his own poison.

OFFTOPIC: Yay, this was my 4000th post here! Running Naked in a Field of Flowers

By l_oliveira

Hero (526)

l_oliveira's picture

29-03-2016, 20:37

Grauw wrote:

What about a mode mirroring only the writes on ports 98H-9BH? Might increase compatibility by a few games and software applications which don’t read the status registers, and rely on the BIOS interrupts.

I did that on one of my test designs. But I'm not the one doing this project. Also that's what Panasonic did with their FS-UV1 hardware. You have read/write access from a mapped I/O address on the FS-UV1 slot and it accept "phantom" writes done to the 98/99 port. But the FS-UV1 purpose is different. It's supposed to be used on a MSX2 computer and on that configuration you will have two identical chips receiving the same writes.

NYYRIKKI wrote:
l_oliveira wrote:

I'd say the main userbase of it would be people who just want to play MSX2 megaroms or use MSX DOS2 and disk based Japanese games.

I expect that you are very much right... It is just that there is no perfect solution and if you want to get past the limitations either you can make the computer to be like other MSX2 machines or you can do plug'n play solution & solve the issues with compatibility with software.

Well, it's positive if we take the existence of these devices as a fact and take measures to make what is produced from now on compatible. That would be a big win.

NYYRIKKI wrote:

OFFTOPIC: Yay, this was my 4000th post here! Running Naked in a Field of Flowers

Cheers !

By NYYRIKKI

Enlighted (5382)

NYYRIKKI's picture

29-03-2016, 20:49

l_oliveira wrote:

Well, it's positive if we take the existence of these devices as a fact and take measures to make what is produced from now on compatible. That would be a big win.

Well... I hope you can sell these enough to take this out of the <0.1% category... at least in peoples minds.

Ok, time for next question:
Are you going to enable possibility to attach these cards to MSX2/MSX2+/MSX tR computers in order to have double display for ie. debug purposes?

By syn

Paragon (1920)

syn's picture

29-03-2016, 22:22

NYYRIKKI wrote:

OFFTOPIC: Yay, this was my 4000th post here! Running Naked in a Field of Flowers

Sorry to burst your bubble but the 4000 is your MRC "score" not the postcount.

Clicking on your profile I see you have "Forumposts posted 3193" Running Naked in a Field of Flowers

Nevertheless congrats on the highscore Big smile

By msxholder

Champion (336)

msxholder's picture

29-03-2016, 22:52

Sooh funny !!
I used the MA-20 for testing msx2 as an replacement for original VDP.
There were several MA-20 's .At that time the idea was upgrading an MSX2
and putting an V9958 in the MA-20 for MSX2+

By l_oliveira

Hero (526)

l_oliveira's picture

29-03-2016, 23:02

It would be a lot of work make a MSX2+ version of it, but would be a lot of fun don't you agree? fzanoto is using V9958s on his unit. Of course it could be upgraded in the future to be a MSX2+ instead. The only problem is for 2+ we would need to make the ROMs from scratch.

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