This message is from the T13 list server.
On Tue, 29 Jan 2002 18:48:46 -0700, Pat LaVarre wrote: >As yet, Atapi UDma includes no protocol for the device to >disclose its opinion of how many bytes it should have quietly >copied into the void, rather than to storage. >I'm asking for the device to have the option to include this >count in the status it reports (ERR = 0, C/D I/O = x03 StatusIn, >residue = 4). I am not an interface chip designer but this does not sound simple to me. In order for this to work we would have to more completely spec how U-DMA works otherwise we could have this problem... A device that just accepts and discards all those "extra" data bytes (after including them in the CRC) just waiting for the host to stop sending data. The host could have been incorrectly programmed to send thousands (no millions!) of extra bytes. But using the Byte Count registers the maximum residue count would be 65535 bytes. This sounds like a real mess that we don't want get near. And something we really don't need to consider. As Jim sort of said... Why change ATA/ATAPI to fix a "broken host" problem? *** Hale Landis *** www.ata-atapi.com *** Subscribe/Unsubscribe instructions can be found at www.t13.org.
