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And we already concluded that in this way you switch out RAM completely, including the stack.

Maybe I didn't get the whole concept of slots then. I thought that, if the 64KB of ROM is in one slot (cartridge), and my MSX's 64KB of RAM is in another, nothing stopped me from having some of the 16KB memory pages pointing to the ROM while others point to RAM. Did I get it wrong?

Keep in mind that I don't mind giving up on RAM or the stack while accessing the highest page ($C000-$FFFF), as it could contain mostly data to be uploaded to the VDP, with interrupts disabled and without the need of RAM or a stack. Whenever I'm not doing that, there will be RAM at $C000-$FFFF. Anything wrong with that?

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I would personally add some mapping facility, like splitting 2x 32K e.g. at 4000. That will leave the upper 16K to current RAM and the lower to the BIOS.

That sounds cool and all, but I don't think I'm ready to make my own mapper yet (I want to keep it simple for now - but still have more than 32KB).

And the thing is that I don't want the BIOS (I'd rather code my own routines, including interrupt) and I don't need RAM at all times. I'd like to alternate the top page between RAM and ROM, whenever needed.

Really, won't that work? I don't see a problem in having the slot completely filled with ROM, since I alternate the highest page between ROM and RAM.

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I really never used any carts on my MSX, but yesterday I bought a "Ligue-se ao Expert" cart, that usually comes with the computer, to make my devcart. Since it comes with the computer, the computer and the cart could have non-standard pinouts than those on that page, and I'd never know. That's why I'm asking.

This is a EPROM cartridge with the BASIC demonstration program from Gradiente. I think that with the addiction of a EPROM socket this would make a good testing cartridge.