Simon wrote:
On 4/21/07, James Richard Tyrer <[EMAIL PROTECTED]> wrote:
But, to the point, IIUC, motherboards with HTX are supposed to be
looming on the horizon. IIUC, this would be as fast as unified
memory architecture.
According to wikipedia, HTX uses DMA, rather than a uniform
architecture:
http://en.wikipedia.org/wiki/HyperTransport#HTX_and_Co-processor_interconnect
"HTX allows plug-in cards to be developed which support direct
access to a CPU and DMA access to the system RAM"
It allows direct connection to a CPU and the CPU has the memory
controller. AMD Hyper Transport CPUs have the memory controller on the
CPU NOT on the northbridge. So something connected to one of the HT
connections on the CPU can directly access to memory.
I think that this is an error in the WikiPedia article. Direct access
to memory is not the same as DMA although a HTX connected device could
have a DMA controller for I/O operations.
HTX is not unified memory architecture, it is NUMA. But, it is just as
fast on the motherboard and something connected with an HTX connector
works just the same as if it were on the motherboard -- the only
limitation is the data transport speed. WikiPedia appears to say that
the connection through an HTX expansion connector is limited to 1.6 GB/s
which is rather fast. But this appears to me wrong since HTX is DDR
which would mean that the maximum was 3.2 GB/s and apparently a 2x link
is possible for 6.4 GB/s.
The WikiPedia article is a little thin. There is a site:
http://www.hypertransport.org
That has more information.
--
JRT
_______________________________________________
Open-graphics mailing list
[email protected]
http://lists.duskglow.com/mailman/listinfo/open-graphics
List service provided by Duskglow Consulting, LLC (www.duskglow.com)
