internal msxdos and scc and game

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By spacegremlin

Expert (80)

spacegremlin's picture

09-04-2016, 21:54

nms8245

i found a pdf how to make an internal msxdos2. some ics have to be added.
i also found a pdf how to make an external msxdos2(with scc) switching to scc and game working.
(but want to inplent it on an internal extra slot)

i want to add the msxdos2 + game and scc internal in the nms8245.
what i want to know, would it be giving memory problems when switch to msxdos2+scc. because the msxdos is also active.

Like when loading programs.
If so it would be better to make an extra option to start with scc only and msxdos2 not active.
I hope i explained my question correctly.

greetings.

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By Wild_Penguin

Hero (590)

Wild_Penguin's picture

18-04-2016, 17:53

Hi spacegremlin,

It would help a little bit if you linked to the instructions you are following, since at least I'm not exactly sure what he modifications you are talking about are doing. I presume the external instructions are for a cartridge that has MSXDOS2 mode and a SCC-game-cartridge, and you can choose with a switch which one is active (but if that is a MegaRAM, a Flash ROM or a ROM cartridge, is not clear from your post).

However, if I'm not totally mistaken, I know that MSXDOS2 ROM and a game ROM/SCC can not reside in the same slot. So what you need in any case, is an expanded slot (free primary slot) or a switch to change which one is active.

Having MSXDOS2 active in itself has little effect on running ROM software. Some disc software written for DOS1 might not run, but there are easy workarounds.

By spacegremlin

Expert (80)

spacegremlin's picture

18-04-2016, 19:10

i have the doc in my pc, but its from the net. but they have different options. but i will go for three switch then.
msxdos2 or scc or scc with game.
There is also an option for msxdos2 and scc. there was my question about.
It would be a scc cartridge with game and addition a rom for the msxdos2 option.

First i want to just make this in the external version, after that its no problem to put it in internal on an extra slot.
if im correct. Because there is if correct a 3rd free internal slot.
with the 3 switch you can just switch to scc without game, and the msxdos2 would be disconnected. so the msxdos1 problem would not be there. i dont think only the scc active gives problems.

Else i will see for a option to disconnect all option. 4 switch.

but i will first begin and see where i end. i also read you need a special msxdos2 rom for this, but that one i have.

thank you. im first waiting for some parts.

By Wild_Penguin

Hero (590)

Wild_Penguin's picture

18-04-2016, 21:41

spacegremlin wrote:

i have the doc in my pc, but its from the net. but they have different options. but i will go for three switch then.
msxdos2 or scc or scc with game.
There is also an option for msxdos2 and scc. there was my question about.
It would be a scc cartridge with game and addition a rom for the msxdos2 option.

Ahh, so there is an option of MSXDOS2 + GAME + SCC, all enabled at the same time? Why do you want to do this? Does the game you want to use, benefit from the presence of DOS somehow?

Anyhow, without having the instructions, it is impossible to tell for sure what they incorporate. But if the above is correct, then you may run into problems:

Having two ROMs in the same slot (active at the same time - i.e. without a switch) may mean the slot is expanded. Bear in mind that the internal slot is probably a subslot - and external slots are usually primary slots, i.e. they are not expanded. A cart with expanded subslots will not work in a subslot, as it will require an unexpanded primary slot (of which there are only 4 in the MSX standard).

All other options (Game, DOS, switchable Game/DOS and all of the previous with or without SCC) should work fine in a subslot.

By spacegremlin

Expert (80)

spacegremlin's picture

18-04-2016, 22:30

maybe i told it wrong. but indeed no option for msxdos+scc+game. that would be useless afcourse.

the options are.

option 1 is msxdos2 with scc (no game ever)
option 2 is msxdos2 or scc without game
option 3 is msxdos2 with scc or scc with game or scc without game and without msxdos.

my option would be because above is mention its possible.

then i think its the best way to use option 3, with a extra option to cut them off all.
but i dont think you would have any problems if you would have a msx with only scc active all the time?
or am i wrong?

And if i am correct the 3rd internal slot is a primaire. thats why i tought about it.

if not a just leave it as a external cartridge, with some extra functions , and we had some fun.

thank you.

By spacemoai1973

Master (165)

spacemoai1973's picture

18-04-2016, 23:45

Hannibal

By Wild_Penguin

Hero (590)

Wild_Penguin's picture

19-04-2016, 10:18

spacegremlin wrote:

option 1 is msxdos2 with scc (no game ever)
option 2 is msxdos2 or scc without game
option 3 is msxdos2 with scc or scc with game or scc without game and without msxdos.

I indeed misunderstood. I think you should have no problems with that setup, even in a subslot!

The only problem I can think of you could run into, would be that some software require the SCC to reside in a different primary slot than main RAM, or floppy drive controller. Well, actually the only one I know is the translated Snatcher (which doesn't mean there aren't others). Majority works no matter where the SCC is, and even if they don't, they let you to choose the slot, usually. So, you can just insert another SCC and use that if they have problems with the one you have built.

So I don't think you'll actually need the switch to disable the SCC. But of course if you run into problems, it might be nice to design it so that you can add one afterwards.

By NYYRIKKI

Enlighted (5484)

NYYRIKKI's picture

19-04-2016, 11:28

spacegremlin wrote:

what i want to know, would it be giving memory problems when switch to msxdos2+scc. because the msxdos is also active.

Because no one here seems to have experience, I'm just as good as anyone else to speculate a bit...

I could imagine that if you use ROM-loaders everything is fine. How ever some disk cracks (like Metal Gear 2 disk version) may search for SCC before loading a game. When this happens I'm pretty sure it will switch DOS ROM away and trying to load after that causes a crash. Is this a major problem? I don't think so, but just something to keep in mind.

By Wild_Penguin

Hero (590)

Wild_Penguin's picture

19-04-2016, 14:31

spacegremlin wrote:

And if i am correct the 3rd internal slot is a primaire. thats why i tought about it.

I just wanted to check (since I've been working with my NMS8255 which is somewhat similar) and it is indeed a subslot. See the service manual page 27. The service manual will be handy if you are going to do modifications inside, in any case. So you have only one internal slot, which means you may want to think over all the alternatives, before using it up. I think that DOS (with or witout SCC) is a good option IMO!

By Bastiaan

Champion (332)

Bastiaan's picture

19-04-2016, 20:15

Option 4; create a third slot based on the documentation you found, and buy a megaflashrom scc+sd.
Than you have 'dos' scc ram mass storage and game options, and some free slots...

By Wild_Penguin

Hero (590)

Wild_Penguin's picture

19-04-2016, 22:55

I think MegaFlashRomSCC+SD requires a primary slot (since it is in itself a slot expander)? So that wont work "on the third slot" since that is already expanded.

Otherwise, I do recommend getting one (and in case you do, you may want to reconsider building in DOS and/or SCC - but they might come in handy, if you do not want to / can not use MegaFlashRomSCC+SD and/or need the primary slots for something else.... YMMV).

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