No Subject

Thank you. Now I understand what to do:
1. setting flag to return memory size needs more logic, but it is more
reliable and more robotic.
2. High address bits R/W enable method saves logic, but leaves a hole to
system, causing trouble even if the chance is
1/1000000000000000000000000000000000000000000000000000000.

Weng

-----Original Message-----
From: Tom Verbeure [mailto:tverb@globespanvirata.com] 
Sent: Wednesday, March 06, 2002 3:04 PM
To: WTX@umem.com; pci-sig@znyx.com
Subject: RE: PCI Configuration BAR all '1' write



See below for comments...

> 
> Hi Amits,
> I may cause confusion. The following is a serial of software 
> reading/writing operations to access the BAR0:
> 
> For power up software:
> 
> Read: 	0x0000,0000		-- initial value
> Write: 	0xffff,ffff		-- try to read back memory size
> Read:		0xffff,0000		-- determine size
> Write:	0x1234,0000		-- memory initial address is:
> 0x1234,0000
> 
> Another software wants to know the BAR0 memory size due to unknown
> reason:

Instead of immediately writing 0xffff,ffff, the other software will
first read the BAR, the write anmd read the 0xffffffff and then write
back the 0x12340000. This is what happens in Windows for example...

** Read:     0x1234,0000
> Write:	0xffff,ffff		-- try to read back memory size
> Read:		0xffff,0000		-- determine size
** Write:    0x1234,0000



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