[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
reading a device's BAR
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: reading a device's BAR
- From: Noam Efrati <noam@genie.terra.co.il>
- Date: Thu, 16 Jan 1997 13:34:47 +0200 (IST)
- Resent-Date: Thu, 16 Jan 1997 13:34:47 +0200 (IST)
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-Id: <"qI1Ht.0.Pp5.5BXto"@dart>
- Resent-Sender: pci-sig-request@znyx.com
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 ?
=========================================================================
Noam Efrati | e-mail: noam@terra.co.il
Terra computers ltd. | phone : 972-7-6483444
Omer Industrial Park | fax : 972-7-6483445
84965 Israel |
=========================================================================
é ,