I have a driver which has been running for several years on 32 bit Windows
XP.
I recently ported the driver to 64 bit Windows XP for x64 and have tested it
using a dual AMD Opteron system.
The driver is for a 32 bit PCI card, using bus master DMA with
scatter-gather lists.
Whilst the x64 system appears to work, I cannot allocate enough map
registers in IoGetDmaAdapter to be able to DMA an area exceeding 1MByte in
length.
Is this an XP enforced limitation? Are there any settings which can be used
to exceed this limitation? I am convinced that I have not yet hit the actual
hardware limit of the motherboard/chipset combination in mapping 32 bit bus
master cycles -> 64 bit system memory address cycles.
Chris Read
If your device only supports 32bit addresses then you are using mapping
registers and you are suffering from the built in mapping register
allocation limitations.
=====================
Mark Roddy DDK MVP
Windows 2003/XP/2000 Consulting
Hollis Technology Solutions 603-321-1032
www.hollistech.com
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Chris Read
Sent: Friday, November 11, 2005 7:45 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] IoGetDmaAdapter NumberOfMapRegisters XP/x64
I have a driver which has been running for several years on 32 bit Windows
XP.
I recently ported the driver to 64 bit Windows XP for x64 and have tested it
using a dual AMD Opteron system.
The driver is for a 32 bit PCI card, using bus master DMA with
scatter-gather lists.
Whilst the x64 system appears to work, I cannot allocate enough map
registers in IoGetDmaAdapter to be able to DMA an area exceeding 1MByte in
length.
Is this an XP enforced limitation? Are there any settings which can be used
to exceed this limitation? I am convinced that I have not yet hit the actual
hardware limit of the motherboard/chipset combination in mapping 32 bit bus
master cycles -> 64 bit system memory address cycles.
Chris Read
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
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