E. C. Masloch

> Regarding the still failing SCANDISK on a RDISK device: on EDR kernel this seems to fail after SCANDISK issues an INT21.440D,084A (lock logical device). The lock logical device call...

I traced lCDebugX's call on `w 100 A: 0 1` and the 084Ah lock call is indeed done by the kernel, not passed to the block device driver.

> > Yes, I think the LFN drive locking is handled by the kernel, not passed down to the device driver. Would have to look into it to make sure...

> So far I understand this. But I do not see the connection to long file name support (this is meant by LFN?). Yes, LFN means Long File Name, introduced...

(l)MS-DOS contains a function in its bios/msdisk.nas file that can use `rep movsd` if running on a 386, and is patched to fall back to `rep movsw` otherwise: https://hg.pushbx.org/ecm/msdos4/file/440e4eb392d0/src/BIOS/msdisk.nas#l2618

By the way, your example is flawed. In a 16-bit CS (including running in Real/Virtual 86 Mode) the default for `movsd` is `a16`, so it will use `cx` as a...

``` ; Load 32-bit divisor (CX:BX) → EBX mov cx, [bp+14] mov bx, [bp+12] movzx eax, bx movzx edx, cx shl edx, 16 or eax, edx ; EAX = full...

I'm fairly sure this bit is also wrong: ``` ; Store remainder and quotient in same stack locations mov [bp+ 4], dx ; remainder.low mov [bp+ 6], ax ; quotient.low...

You'll have to move backwards to directly move from 00600h to 00700h. And you need a small relocator stub to execute outside the kernel data.

I updated the thread in https://github.com/SvarDOS/edrdos/issues/28#issuecomment-2248801739 with a new comparison of compression methods, including one that just adapts the zerocomp that originates with DR-DOS but applies it to the entire...