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reading a device's BAR




Hi all,


As I understand the way a PCI driver should be written, the BAR register 
should be read from the device for each access of the application to
the PCI target, in order to know its location in the PCI address space.

Synce this is done by calling the BIOS interrupt routine (Read 
Configuration Dword), it takes about 10 microseconds (I checked it on 
a pentium machine, I don't know the time it would take in other systems
like ALPHA-PC or alike).

This means a latency of 10 microseconds for reading/writing a PCI device 
!!!


Am I right, or am I missing something ? 



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Noam Efrati                    | e-mail: noam@terra.co.il  
Terra computers ltd.	       | phone : 972-7-6483444	 
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