Original games use rarely more than 64kB but DOS2 needs 128kB minimum. Cracked megaroms and some other games use often more than 64kB (usually 256kB). 1024KB is very good for a general use.
About turbo R, It an exception. External memory mapper is never selected as main RAM. In addition, the RAM of the MFR is ignored in R800 mode when the computer is turned on because the FPGA does not quickly enough initialize. That are why I recommend a MFR without 512kB if you take a turbo R.
Original games use rarely more than 64kB but DOS2 needs 128kB minimum.
Seems like quite a few homebrew European games require 128kb RAM, actually, including almost all the Stichting Sunrise titles. And only some of these games work with cartridge RAM expansion -- I can play Bombaman, Pumpkin Adventure 3, The Lost World, and Akin with my Musical Memory Mapper cartridge, for example, but I can't play The Witch's Revenge (beyond part of the intro, anyway), The Shrines of Enigma, or Pixess. And every one of those games is just plain unplayable with my base 64kb RAM.
Original games use rarely more than 64kB but DOS2 needs 128kB minimum.
Seems like quite a few homebrew European games require 128kb RAM
The difference between non-professionnal MSX2 computers explains that: most European MSX2 computers have at least 128KB RAM while most Japanese MSX2/2+ computers have only 64KB RAM.
In addition, the RAM of the MFR is ignored in R800 mode when the computer is turned on because the FPGA does not quickly enough initialize. That are why I recommend a MFR without 512kB if you take a turbo R.
That is not right. The RAM is not counted, sometimes, at boot. But that does not mean it is not available to use it.
So, the RAM in MFR SD can be used in turbo R always.
I'm not saying that RAM is unusable. I know if we reset the Turbo R when ignored, the RAM can be used again but it's better to upgrade the internal RAM of Turbo R than taking the MFR with 512kB for use on Turbo R only.
External memory mapper is not selected as main RAM on turbo R except perhaps in z80 mode.
You don't need to reset to use it. The RAM is never ignored as you said. The RAM is always available after power on.
And as ToriHino said, you can use the RAM in the cartridge as main RAM on turbo R just holding 4 at boot.
What I said there is that only the memory count displayed on the turboR boot screen is sometimes off due to FPGA initialisation time, but other than that the memory is usable and detected fine by DOS2 as well. So Guillian is correct, and there’s nothing defective.
