[hatari-devel] Falcon DMA doesn't allow reading/writing of more than 16383 sectors

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(cross-posting to emutos-devel and hatari-devel as it concerns both)

Hi,

in case you have missed it, thanks to a joint effort an interesting fact has been uncovered: https://www.exxosforum.co.uk/forum/viewtopic.php?t=7983.

TL;DR version is that on Falcon one should never request more than 16383 * 512 bytes in one go when accessing SCSI (as a DMA device) because its internal counter is limited to 14 bits. This has been confirmed not only in practice but also by several notes in AHDI source code.

AFAIK a new version of HD Driver is in the cooking (which didn't have this limit implemented) so maybe both EmuTOS and Hatari devs can check whether it is something they would be interested in following (for example now Hatari happily accepts the full range i.e. not locking any desktop transfers).

--
http://mikro.atari.org


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