Technical Q&As

HW 07 - Disconnect/Retry (15-July-95)

Q My PCI card, which is not a bus master, has to move large quantities of data internally (i.e., not over the PCI bus), and a block transfer of this type, if uninterrupted, should take 150us to complete. However, when my PCI interface responds to a request from the PCI bus, it issues a target-initiated disconnect-with-retry until the circuit on my card is ready to deal with the PCI request. How long (or how many times) will the Macintosh tolerate the target causing a disconnect-with-retry ?

A As long as your card issues "retries" after the disconnect, it can hold off the Master for an indefinite length of time.

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