Not ready for a new build yet, but did just check in 5.4a with fixes for Resetting MSX megaROM games (128K or larger).
And a really nice improvement for 256K and 512K games. Right now I'm using the spare 128K of VRAM as a fast-copy buffer... and if the ROM is larger than 128K I don't use it. Which is silly... for example, on a 256K ROM, I can still put HALF of the ROM in the fast VRAM buffer. Half-fast (say that 10 times fast) is better than all-slow. So now 256K and 512K games get a speed boost especially if there is a lot of bank switching happening in the lower 128K.
And a really nice improvement for 256K and 512K games. Right now I'm using the spare 128K of VRAM as a fast-copy buffer... and if the ROM is larger than 128K I don't use it. Which is silly... for example, on a 256K ROM, I can still put HALF of the ROM in the fast VRAM buffer. Half-fast (say that 10 times fast) is better than all-slow. So now 256K and 512K games get a speed boost especially if there is a lot of bank switching happening in the lower 128K.