Re: Dealing with GPU code

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Phil Taylor (phil_at_private-citizen.com)
Date: 01/14/05 

Date: Fri, 14 Jan 2005 10:27:23 -0800

the mechanism may be driver dependent.

could be DMA, MMIO, or private transport. whatever mechanism the driver
writer felt was most performant and flexible for their situation. and may be
dependent on resource being transferred and whether its PCI, AGP, or
PCI-Express as the bus technology.

for instance, textures cannot be rendered from system memory but can be
rendered from AGP. so how the driver treats textures from the CPU to the GPU
is different based on a combination of bus and behavior flags.

drivers also typically pre-swizzle command and data into hw specific formats
before the transfer to the device. esp if WRITEONLY flags are used. so again
how the driver treats the resource may be flag dependent, as unswizzled
resources may take a different path to the device.

search on 'xbox push buffer' to see what 1 hw specific implementation does.
different flavors of hw from the same IHV can have variation, different IHV
hw architectures can be somewhat different. but the general idea is there.

given this has zero impact on user code, and gives you zero insight into how
to use the API ( with the exception of readbacks but they are already a
special case ) - why would you care?

"Jacky Luk" <jl@knight.com> wrote in message
news:ugruy6f%23EHA.2700@TK2MSFTNGP14.phx.gbl...
> Dear all,
> Like Shaders code, how would the CPU deal with GPU instructions in terms
> of
> transferring the inst to the AGP interface ? using mapped I/O or what?
> Thanks
> Jack
>
>

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