RE: Newbie question: What are map registers really .. .

> That’s a terrible truth. How can I avoid additional copying data by kernel

DMA support?

Set ScatterGather member of the device description to TRUE.
This will force IoMapTransfer/GetScatterGatherList to skip double-buffering
and just return you the values from the tail of the MDL without any mapping.

Max


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Only when my portable computer routinely has more than 4GB :slight_smile:

Mark Roddy
Windows 2000/NT Consultant
Hollis Technology Solutions
www.hollistech.com

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Paul Bunn
Sent: Monday, February 12, 2001 8:42 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Newbie question: What are map registers really … .

Aren’t crappy 32bit PCI devices limited to the first 4GB of RAM
in the same
pathetic-limitation way ? :wink:

Regards,

Paul Bunn, UltraBac.com, 425-644-6000
Microsoft MVP - WindowsNT/2000
http://www.ultrabac.com

-----Original Message-----
From: Mark Roddy [mailto:xxxxx@hollistech.com]
Sent: Monday, February 12, 2001 5:29 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Newbie question: What are map registers really …

> Mark Roddy is, as usual, right on target with this answer. On
> small detail
> is that that the map registers are in fact allocated below 16MB
> physical (in
> A24 space) on systems with ISA buses.
>
> Peter
> OSR Open Systems Resources, Inc.
>

Ah yes, the ‘on small detail’ done got me again :slight_smile: Peter is of course
correct that the ridiculous ISA bus can’t even address 64MB, no
it can only
address 16MB, and thus MAP registers are forced to be located below 16MB.
Yet Another Reason To Banish ISA Forever.

Mark Roddy
Windows 2000/NT Consultant
Hollis Technology Solutions
www.hollistech.com


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