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> "Mcgrath, Jim" <[EMAIL PROTECTED]> 12/12/01 07:44PM > a host with small amounts of buffer memory > can set up a physical buffer smaller > than the command transfer size Yes the asic's I work with are silicon-bound rather than i/o-bound in part because their buffers are small and inside - in the 2KiB to 32KiB neighbourhood: they don't have enough pins to connect to a cheap parallel memory outside. I didn't mention this because I didn't know it was significant. >> [EMAIL PROTECTED] 12/12/01 06:57PM > Do you think that a DMA burst > is always equal to a media data block? ... not Agreed, thank you for clarifying. > a DMA burst ... a media data block ... > there is *NO* relationship between this two things. In Pio many of our asic's pause at block boundaries in order to TalkLikeWindows. We have a history of pain involved in enumerating which Pio devices shipped by other people behave badly if you don't pause at block boundaries. I'm clear on how a UDma sender can pause at block boundaries ... I'm not clear on how to use this history of Pio pain to guide life as a UDma receiver. My best guess is to have the receiver try to cooperate with a sender who delays for at least a turnaround at block boundaries, for example after bursting one block while still reading the next from slow media. I figure if the receiver always pauses transfer except when a whole block is free, if the sender always delays for a turnaround at block boundaries, then all pauses will occur on block boundaries, which shouldn't matter, but might. Clearly a better way to TalkLikeWindows would be to add more buffer, but that would cost dollars, so I can't effectively advocate that until after I actually prove we need to use Dma to connect with devices broken enough to need to connect to large buffers like Windows has. Pat LaVarre Subscribe/Unsubscribe instructions can be found at www.t13.org.
