This message is from the T13 list server.
On Thu, 21 Mar 2002 08:20:17 -0700, Pat LaVarre wrote: >This message is from the T13 list server. >>> Jim McGrath said: >>> Later people started using SEEK >>> as a poor man's attempt to overlap commands >Yes. But this never really worked, because... >>> (since SEEK actually completes immediately, >>> allowing the ATA bus to be freed for use >>> by a second drive while the first is still seeking). >Ansi T13 never published this fact anywhere, did it? Correct! And by 1992 there were many drives that had the SKC status bit tied to the DRDY bit at all times even during SEEK commands. Maybe if the original CAM ATA document or ATA-1 had documented this use of SKC this would not have happened. But we know that even back then most host software was doing a byte compare on the ATA status for the value 50H... Not doing bit testing for 40H/10H/etc. >Do Ata drives actually now commonly implement overlapped commands? No. And why is that? Because (really do I have to say this again?) we can thank the host adapter folks for not providing us with high performance host side hardware. (There I said it without putting the word Intel or stupid in the sentence.) *** Hale Landis *** www.ata-atapi.com ***
