Re: busmaster question

[Russell King <rmk@arm.linux.org.uk>]

On Sat, Apr 28, 2001 at 01:27:30AM -0500, daniel sheltraw wrote:
> I have a busmaster question I am hoping you can help me with.
> If a PCI device is acting as a busmaster and the processor initiates a 
> read/write to another device on the PCI bus while the busmater-device is in 
> control of the bus what happens to the instructions initiated by the 
> processor? Are they never seen by the device that the processor
> is trying to read/write?

The access by the processor is delayed until the PCI arbiter allows the
CPU access to the PCI bus (how long depends on all sorts of things which
I won't go into, but its not necessarily held off until the end of the
busmaster transfer).

--
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html