Yo All!
On Fri, 20 Oct 2000, J . A . Magallon wrote:
> AFAIK, AGP is just a preferent PCI slot in the PCI bus; that is for you can
> only have ONE AGP port on a PCI bus.
No. The AGP bus is never ON a PCI bus.
To quote the AGP 2.0 spec section 1.2:
"A.G.P. neither replaces nor diminishes the necessity of PCI in the system.
This high speed port (A.G.P.) is physically, logically, and electrically
independent of the PCI bus."
"The A.G.P. interface specification uses the 66 MHz PCI (PCI Local Bus
Specification) specification as an operational baseline, and provides four
significant performance extensions or enhancements to the PCI specification
which are intended to optimize the A.G.P. for high performance 3D graphics
applications. These A.G.P. extensions are not described in, or required by,
the PCI Local Bus Specification. These extensions are:
· Deeply pipelined memory read and write operations, fully hiding memory
access latency.
· Demultiplexing of address and data on the bus, allowing almost 100% bus
efficiency.
· New AC timing in the 3.3 V electrical specification that provides for
one or two data transfers per 66-MHz clock cycle, allowing for real data
throughput in excess of 500 MB/s.
· A new low voltage electrical specification that allows four data transfers
per 66-MHz clock cycle, providing real data throughput of up to 1 GB/s."
So they started with the PCI spec, but they changed the logical meaning
of a lot of the bus signals, they added a lot of bus signals, they run it
about 8 times faster, they changed the voltage and a bunch of other stuff.
I say it is a different animal now.
> Please, could an expert point to the AGP standard defs ?
http://developer.intel.com/technology/agp/
The spec itself is at:
ftp://download.intel.com/technology/agp/downloads/agp20.pdf
In any case, I do not see how this topic belongs on the l-k list.
Contact me off-list if you need more info.
RGDS
GARY
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Gary E. Miller Rellim 20340 Empire Ave, Suite E-3, Bend, OR 97701
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