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Hale L:
Ouch, sorry again, I keep wasting your time, you & who knows how many other folk here
too. I'm caught fast in that programmer's illusion of "I just fixed the last bug". I
keep thinking we almost understand each other.
Friday, an engineer from .co.jp wrote me offline to confirm understanding offline -
there I was entirely understood. And Jim & I seem to be connecting - have you read
that traffic too? And Sbp2 folk & I seem to be connecting here.
We're talking about Scsi-over-whatever that just plain works vs. Scsi-over-whatever
that only mostly works. We are by definition talking about the less normal situations.
Let me try one more time to connect with you over your Dma examples. Can we agree
traces such as the following two are common?
Dma:
3 "words" clocked In across the bus
Pio:
BSY DRQ C/D I/O = 0 1 D I
x1F5:1F4 ByteCount = x00:05
3 "words" clocked In across the bus
If you don't like these examples, can you tell me what's wrong? What have I not
reproduced from your examples that matters?
I read your examples to be saying that in both of these traces we see:
3 "words" clocked In across the bus
I agree. Of course. Goes without saying. The bus is two bytes wide. Yes.
I hear you saying that x86 folk copy In 3 "word"s only via 3 REP's of INSW. I
disagree. I see people using 2 REP's of INSW followed by an IN AX followed by a MOV
AL. I see 5 bytes copied In, not 6, in Win98 & WinMe.
I say this is a kind of double-buffering, one kind among many.
I hear you saying it's not a T13 problem if in the new Dma trace the host copies In 6
bytes whereas in the similar old Pio trace the host copies In 5 bytes.
I'm saying that Pio works and Dma doesn't is a T13 problem. Who above he level of T13
cares if we're using Pio or Dma?
It is the BSY DRQ C/D I/O ByteCount info that tells the host to copy In just 5 bytes.
T13, me included, we left I/O and ByteCount out of Atapi Dma, whoops.
Sure you're free to disagree. But are you telling me I am incoherent? Can you not
see my point of view? T13 used to pass info across the bus that it passes across the
bus no longer. Me & friends, we were using that info. Then 17e+6 byte/s began to
feel constricting. Then I noticed T13 had deleted that info. Now here I am.
Am I any clearer yet?
Yes I am saying UDma has a further issue past that, yes I hear you say no, but if we
can I'd like to defer assessing my UDma claim until we get consensus on at least how
broken Atapi Dma is as a Scsi-over-whatever mechanism for copying odd counts of bytes.
My offer to connect by phone & pager remains open.
Pat LaVarre
