This message is from the T13 list server.
On Fri, 12 Apr 2002 08:33:01 -0600, Pat LaVarre wrote: >This message is from the T13 list server. Hale said: >> In my opinion trying to make ATA/ATAPI >> work like some other interface >> shows a lack of understanding >> of the basics of ATA/ATAPI. Then Pat said: >In my opinion, trying to think of Atapi as anything other than >yet another Scsi transport shows a lack of understanding of the >basics of I/O subsystem design for a plug 'n play O.S. (See my previous email about the Inquiry command)... But here again is the confusion I see in your statements. If a system has a USB interface and you attach a SCSI device (that is really a bridge) then that device needs to conform to the SCSI standards for that type of device. That means that the Inquiry byte would not be 0x00 even if the real device behind the bridge was an ATAPI device that had 0x00 in that Inquiry byte. IN OTHER WORDS: THE USB-to-ATAPI BRIDGE MUST PERFORM THE CORRECT AND PROPER COMMAND SET EMULATION! Please stop trying to make this into a T13 ATA/ATAPI problem. And it probably isn't a T10 problem either. The problem is the failure of these bridge devices to perform their job correctly! >There's no standard place to claim, for example, that a >particular Atapi device will copy In 6 bytes via Atapi Dma if it >would have copied In 5 bytes, given precisely the same -x 12 0 0 >0 05 0 "Inquiry of additionalLength" command. The ATA/ATAPI interface is 16-bits wide. ALL ODD TRANSFERS WILL BE ROUNDED UP TO THE NEXT EVEN VALUE. This is just one of those things we know, sort of like we known the sun rises in the east. A properly implement X-to-ATAPI bridge needs to know this and handle it, especially if the X side can't handle that extra pad byte. Again, the bridge must be properly implemented and do its job correctly! >http://members.aol.com/plscsi/ftf.html >exists to present a >scheme for comparing one Scsi transport with another, sorted to >present the actual consequences of this lack of correlation from >the most commonly to the most rarely observed. Just curious... Are you trying to do what those original SFF-8020 people tried to do? That is redefine ATA/ATAPI or SCSI to your way of thinking without bringing proposals to T13 or T10? (Sure sounds that way to me.) But I think the actual problem here is the wish to make X-to-ATAPI bridge devices that are super cheap and somehow cheat and don't perform the true task that needs to be performed. That's fine and maybe there is a big market out there and such products would be very sucessful... But... Trying to change 8+ years of history and ignoring the approved and established interface standards in order to make these bridge devices is probably doomed to failure in the long run. Of course the business model for success here is well known... Just form a "secret society" with a strongly worded NDA, hold secret meetings, issue glowing press releases about how great things will be and ... (need I say more?) *** Hale Landis *** www.ata-atapi.com ***
