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From: Michael Polo <mpolo@vitana.com>
Newsgroups: comp.os.ms-windows.programmer.nt.kernel-mode
Subject: Re: Bus Master DMA: memory limit  to HalAllocateCommonBuffer?
Date: Fri, 07 Nov 1997 10:37:55 -0500
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I had a similar problem allocating memory using the function mmMapIoSpace or
something.  While I did have less memory, paging should allow you to allocate
as much as 4 gigs.  To solve my problem I increased the number of pages via the
system registry as well as increasing the virtual memory allocation. After that
I had no problems.

Hope this helps.....

Mike Polo

Anthony Corriveau wrote:

> I'm writing a simple Kernel Mode driver to support a PCI busmaster DMA
> device.
> The call to "HalAllocateCommonBuffer" fails if I try to allocate more than
> 18meg.
> Sometimes it will fail trying to allocate as little as 4meg. I have 128 meg
> of ram,
> so I should have plenty of free physical memory.
>     The call to "HalGetAdapter()" always returns NumberOfMapRegisters=0x10.
> This doesn't follow what is
> in the documentation, which says MaxMemory=NumberOfMapRegisters*PAGE_SIZE.
> So my maximum should be 0x10000 or
> 64k bytes, not 18meg!.
>     Does anyone know what the limits of HalAllocateCommonBuffer are?
> Does any have any more details on this? the DDK is pretty cryptic.
>
> Thanks ,
>
> Anthony Corriveau
> acorriveau@ldg.com
> SBS Embedded Computers
> Raleigh NC