1.44 BM dsk image

Actually the disk ROM might just take a 1.44MB image. Emphasis on might… you can’t format a disk on MSX that way but I’ve seen MSXs understand different formats just fine. Just try and see what happens.

The Gotek will have no issues, but the HD formats use more sectors per track than the DD formats, and the flux changes themselves happen at higher frequency to support this. (That's how they get more data on a diskette when they have the same number of sides and tracks/cylinders.) So the floppy controller hardware would need to support this higher data speed, and the software running it would have to be programmed understand and expect this format and the controller's higher-speed support.

There's actually a few limitations coded into the diskrom.

• The manufacturer specific hardware driver will have drive parameter blocks for supported formats. Basically, these will tie media descriptor bytes to physical floppy formats. The media descriptor (0F0h) for the 1.44MB floppy format is not in that list.
• The hardware driver will also return the highest number of FAT sectors of the supported formats. For 720K disks, this will be 3. The diskrom will reserve RAM in the system area to store a copy of the FAT for all drives. So floppy A: and B:, that's 2 * 3 * 512 = 3072 bytes. A 1.44MB floppy will have a larger FAT (even 9 sectors, because it uses 512 byte cluster size), and the hardware driver needs to be patched to reserve this space. Of course, this will greatly reduce the amount of free space in MSX Basic.
• As cjs already pointed out, a 1.44MB floppy will have a higher data rate. I have no idea if the diskrom will be able to handle this.

I have done a small test with a 900K floppy image in the past, by modifying the first sector of the disk. That test failed, because of the drive parameter block mentioned above (which I didn't know at the time). I could re-run the test with a modified diskrom and see what happens.

(by the way, I tested this on openMSX, not on a real machine with Gotek)

Maybe a track to follow in the guessings about that: the Daisen Sangyo MX-2021. This professional machine can have as peripherals to be added inside:

* MX30A - internal 2DD floppy disk drive - ¥38,000
* MX30B - internal 2DD/HD floppy disk drive (with built-in MSX-DOS 2) - ¥52,000

Note the presence of MSX-DOS 2 for the version with HD support. Maybe the MSX turbo R could support HD too? Or it is impossible on purpose?

i tried a lot of times, can you help me ?