Cartridge Games on a Classic CPC.

[Bryce]

Last night while updating my "Hardware Wish-list" I was pondering a new idea: Making a Cartridge Port for a Classic CPC. The idea being that you could plug a Plus/GX4000 Cartridge into a Classic CPC (ACID not required). But I dismissed the plan, because I think most cartridge games probably use Plus features that wouldn't work anyway. Is this really the case? Do all/any/most cartridge games make use of the Plus features? Or would they actually work on a Classic CPC if connected?

Bryce.

[arnoldemu]

Last night while updating my "Hardware Wish-list" I was pondering a new idea: Making a Cartridge Port for a Classic CPC. The idea being that you could plug a Plus/GX4000 Cartridge into a Classic CPC (ACID not required). But I dismissed the plan, because I think most cartridge games probably use Plus features that wouldn't work anyway. Is this really the case? Do all/any/most cartridge games make use of the Plus features? Or would they actually work on a Classic CPC if connected?

Bryce.

You are correct, all cartridges use some plus features.

Barbarian II for example uses the Plus's "Secondary ROM mapping" register to say the page of the cartridge in the upper &c000-&ffff, and which page of cartridge in the lower &0000-3fff (but does depend on setting).

*BUT* It would be possible to make a CPC cartridge that is designed just for CPC, and you override OS and roms to make it, but I don't think it would end up cost effective or practicle, considering the megarom does all of this (excluding overriding OS rom) already.

[MacDeath]

Would such thing need to connect to the extension port (fully external, no soldering/mod on the CPC itself) or would it need to connect this to the Actual ROM sockets on the motherboard (trickier) ?

[arnoldemu]

Would such thing need to connect to the extension port (fully external, no soldering/mod on the CPC itself) or would it need to connect this to the Actual ROM sockets on the motherboard (trickier) ?

All external is ok, but you would need to exclude rom 7 (or make a hardware modification).
But a cart with 252 roms is nice

[Bryce]

The plan was for all external. But I have just deleted the idea from my wish list, due to the information arnoldemu has just supplied.

252 ROMs is of course possible. That would be 4MB in total, but would it be useful? For what? It would also be physically large: The largest EPROMs are 512K so you'd need 8 of them and it would probably need a separate power supply too.

Bryce.

[SyX]

Well, IF in the future we can produce new CPC+ cartridges for new software, how happens in the Atari, MSX and C64 world, in that case a cartridge port for the Classic CPC could be useful, and surely it would be more easy make cartridges that find new 3" floppy disks... but i think it's more sensible use USB or SD in our CPCs

[steve]

The danger is that cartridge software would be written to run on the CPC, not using the plus features, so instead of speccy ports(which would still happen), we would get CPC ports, leaving the plus features unused.
Sure software could be written to test which machine it is running on, but would that actually happen if some ebayer thought he could make a lot of money by simply putting CPC software on cartridge?

[TFM]

Now, what's a cartridge? Nothing else than an EPROM card ;-) So, no need to add it to the CPC old generation, just use the MegaROM ;-)

[TFM]

All external is ok, but you would need to exclude rom 7 (or make a hardware modification).
But a cart with 252 roms is nice

Well, one of my CPCs has 2.5 MB internal Flash, and since this is internal every ROM can be rewritten. Really a nice thing, and the internal 4 MB RAM just round it up. You can get that mod from Jarek btw.

I also like the idea of the "lower ROM-RAM-Box" ;-)

[Bryce]

A cartridge isn't quite the same as parallel ROM. The cartridge has direct access to the entire 512K, whereas ROMs are patched into memory in 16K Blocks, so lots of bank management has to be included in any software that crosses the 16K barrier.

By the way: Is there a cartridge version of FutureOS? That would be handy for the tests I'm doing at the moment.

Bryce.

[TFM]

A cartridge isn't quite the same as parallel ROM. The cartridge has direct access to the entire 512K, whereas ROMs are patched into memory in 16K Blocks, so lots of bank management has to be included in any software that crosses the 16K barrier.

The CPCog (old generation) will not get new banking capabilities by adding a cart.
Furthermore the address bus of the Z80 is in CPCog and CPC Plus 16 bit, so you can address 64 KB, but never the entire 512 KB at once.

By the way: Is there a cartridge version of FutureOS? That would be handy for the tests I'm doing at the moment.

Not now, I had planned to make one, but missed time. Well, I should come back to this idea probably. I'll let you know as soon as I find time to make one.