I just got myself an 1Mb external mapper... was very happy that I could finally play Metal Gear 2, but it didnt work at all 
The problem is that I'm trying on a turbo-R A1ST, which already has 256kb of internal mapper, and every thing I tried, only detects this internal mapper.
I have tried the disk english translation (only recognizes the internal mapper and plays without any sound); I have tried both LoadROM and Megamu (both hangs after loading and only finds the internal mapper). I heard about TRLoad, but couldn't find it, and I'm not very hopefull it will find the external mapper...
All tests were done all win Z80/R800 ROM and R800 DRAM modes, with the mapper on both slots 1 and 2, all the same results.
I have tested the Mapper cartridge with TestRAM, and it's ok. Also the same things I tried on openMSX (emulating A1ST with external mapper) and all programs behave the same.
Is there any hope for me? Any program that finds a secondary mapper that could load Metal Gear2? Any other game that uses the extra memory?

