Installation on PC disk

[mikro]

Hello,

is there any chance HD Driver will get an option to install on drive partitioned as MBR/PC partition scheme? (4x16 bytes partition headers). For normal TOS it makes no sense of course (as it expects AHDI/Atari scheme root sector) but for example on CT60, we've got a support for it, so patched TOS is looking for MBR on such disk and try to load something...

[mikro]

Btw, one (probably) bug report regarding this: when I use PC partitioned card and choose "Partition" in HD Driver menu, I see correct sizes but no IDs ($06 in my case). I guess it should be there as when doing partitioning actually, I can write it there ($06, $0b, $83 etc)

[uweseimet]

For DOS partitions $04 and $06 are not displayed on purpose, just like GEM and BGM are not displayed for TOS partitions. These values are the standard values for these types of partitions and the user should not be bothered with them since HDDRIVER has to use them anyway in order to create valid partitions.
Only non-standard values are displayed.

Besides the partition scheme there are also other issues to consider (byte order in particular or the ability to boot) when thinking about whether it may be useful to install HDDRIVER on PC-compatible media. Upcoming versions of HDDRIVER may lift some restrictions for certain platforms (in particular the Suska board) but in general it will not be possible to support all kinds of (patched) platforms.

[mikro]

Thank you for clarification. As I don't know what do you plan for Suska, would it be at least possible to make everything PC compatible (MBR partition table + VBR for each partition) and just insert HD Driver boot code? In this way, no byte swapping would be necessary, as boot code is just array of bytes for any OS. I don't know how much work is it for you but it would be amazing to have something like that. Bootable on Atari, usable directly on PC.

[uweseimet]

Depending on whether you have an IDE or SCSI drive connected to your PC the byte order is different, i.e. byte swapping definitely is an issue. The IDE byte order used by the Atari is big endian, for the PC it's little endian. With SCSI drives the byte order is big endian for both platforms.
So it takes at least a modified TOS that handles the byte order issue before you can think of booting from PC compatible partitions.

[mikro]

Excuse my trivial question but about what bytes we're talking now? I thought boot process is just about loading first 512 bytes from disk, executing MBR/boot sector and let HD Driver to take care about the rest. Am I missing something important here? On what place is that endian conversion needed?

[uweseimet]

TOS cannot execute code on root and boot sectors if the data on these sectors have the wrong byte order. The data would have to be swapped first, but TOS does not do that, which means TOS cannot load the hard disk driver. This may work with a patched TOS or hardware that automatically does the byte-swapping.