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Why would anybody ever use ACA with either BOT (that doesn't support it) or UAS? It's basically a solution in search of a problem, since it is needed when comm
by bonzini 6y ago
Why would anybody ever use ACA with either BOT (that doesn't support it) or UAS?
It's basically a solution in search of a problem, since it is needed when commands are delivered asynchronously with respect to responses but you don't have autosense. BOT only has a single command in flight so it didn't need ACA, but UAS has autosense so it doesn't need it either...
- hlandau 6y agoAuthor here. I'm no expert on the problems ACA was intended to solve, but if I understand it correctly, I could see some remaining applications for it. Suppose I schedule 10 commands all at once, with the Ordered task attribute. If the third command fails, do I necessarily want the remaining commands to be executed? Possibly these are a logical sequence (e.g. for a tape drive, rewind, write, etc.) I have no idea if anything actually exists which can make constructive use of ACA in this way, but it occurs to me that there is still potentially some use there even when autosense is enabled. That is, if I'm understanding ACA correctly.
- bonzini 6y agoTrue, the problem is that no one has ever implemented ACA in the target. :-) So it does not really matter if the transport supports it.