[Pc_Support] Re: AMD buys ATI, is this good or bad -- this will *ELIMINATE* ATI's proprietary kernel driver

[Bryan J. Smith]

On Tue, 2006-07-25 at 09:30 -0400, Bryan J. Smith wrote:
> Intel's current platform "bus" interconnect makes this _impossible_.
> That's why Intel has not moved past using AGP and, now, PCIe -- both I/O
> interconnects -- as video interconnects.  It uses 100% _software_ to
> maintain CPU to GPU coherence, because it's CPUs _lack_ anything else.

As I regularly point out, this "100% _software_ to maintain CPU to GPU
coherence" is virtually 99% of the reason why ATI and nVidia have
proprietary kernel drivers**.  Unlike other I/O peripheral cards that
merely do "DMA" transfers to/from the system memory, video cards do,
what Intel calls, "Direct in-Memory Execution" (D[i]ME).  In other
words, it acts like a CPU -- using memory _directly_.

[ **NOTE:  The proprietary kernel drivers should _not_ be confused with
the proprietary XFree/Xorg (X11) driver and related LibGL library and
resulting GLX (OpenGL over X11) support.  Those drivers are _allowed_ by
both the XFree/Xorg license.  The kernel driver is used for memory
_performance_ at the kernel level, which is more questionable. ]

The code that both ATI and nVidia use is an Intel _trade_secret_.

For the longest time, Intel even considered the AGPgart to be a trade
secret.  Back then, only nVidia (not ATI) has chipsets, which is why the
nForce AGPgart wasn't part of the stock kernel.  Once PCIe came out,
Intel stopped considering its AGPgart as a trade secret, so nVidia was
able to add the nForce to the stock kernel.

Now I'm sure you're saying, "Wait as second Bryan!  Intel's own chipset
AGPgarts are in the kernel, and Intel doesn't have proprietary kernel
drivers!  So you're wrong!"

And my response is, as always, "Have you seen the performance of the
Intel drivers on Linux versus Windows?"  Yeah, that's right, it _sucks_.
Intel's AGPgart and [almost total lack] of a GPU support driver _kills_
performance on Linux.  Memory coherency is _everything_.  

So what's this have to do with ATI-AMD?

AMD's I/O MMU and inter-CPU coherence is in the CPU.  It's _hardware_,
not a flaky set of software and hacks, like Intel.  So not only do we
get a _stable_ way for the GPU to access system memory, because it's now
on the system interconnect instead of a peripheral card trying to act
like a local CPU with software hacks -- but it will *ELIMINATE* ATI's
proprietary kernel driver.

I've said it before and I'll say it again -- Intel has been the problem!
Not ATI.  Not nVidia.  *INTEL*.  And this move by AMD will *ELIMINATE*
it, at least for ATI.  ;->

nVidia will have to decide if it wishes to support AMD's new HTX GPU
standard.  And although it owns ATI now, I believe it will work with
nVidia to do so.  Because freezing Intel out of the high-end GPU market,
or forcing Intel to _redesign_ their _entire_ platform to support it
(which will take at least 18-24 months -- possibly longer for stable I/O
MMU support which AMD took a bit to learn with the Athlon MP and AGP) is
more of a marketing strategy than "beating nVidia" with its ATI arm.


-- 
Bryan J. Smith          Professional, technical annoyance
mailto:b.j.smith at ieee.org    http://thebs413.blogspot.com
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