Re: [hatari-devel] Systematic launch tests

[Vincent Rivière <vincent.riviere@xxxxxxxxxxx>]

On 26/03/2017 à 22:37, Roger Burrows wrote:
> IIRC, there's no guaranteed way of detecting a byte-swapped Atari
> partition table, so EmuTOS doesn't attempt to guess.

Ahem, this is on my EmuTOS TODO list... for Amiga.
This is because Amiga has a naturally byteswapped IDE port (like PC). When 
you plug an Atari formatted IDE drive on Amiga, EmuTOS can't use it because 
of this current limitation: need for software byteswap is not properly 
detected. It should be, definitely. (as Roger said, EmuTOS works fine in any 
case for PC-formatted IDE disks)

That being said, there is a second issue, related to Hatari.

It seems that Hatari systematically byteswaps IDE disk images (is this 
true?). This is good if someone plugs an Atari IDE disk on PC and mount it 
in Hatari as IDE: it will appear as normal (non-byteswapped) in the Atari 
OS, which is best for performance.
But if the disk image is a clean (non-byteswapped) image (i.e. image of ACSI 
or SCSI disk), it will appear as byteswapped when mounted on Hatari IDE. 
Hence bad performance, or even unusable with current EmuTOS.

The solution is to add a "byteswap" option in Hatari when an IDE image is 
used. If the original image is clean (can be easily checked with xxd), then 
"byteswap" should be unchecked. If the original image is byteswapped (or 
simply /dev device of Atari IDE disk plugged on PC), then "byteswap" should 
be checked. So Hatari will always do the right byteswap, and the emulated 
IDE disk will always appear non-byteswapped in the Atari OS, for best 
performance.
FYI, ARAnyM has similar option, even if it is IMHO reversed, of not 
completely buggy for whole disks.

--
Vincent Rivière