[H-GEN] question

Christopher & Lisa LeMoyne dragonthrone at iname.com
Tue Nov 2 02:22:06 EST 1999


[ Humbug *General* list - semi-serious discussions about Humbug and
Unix-related topics. ]


>Someone else said (paraphrasing) "the ISA and PCI busses are directly
connected,
>the AGP is not". This is a complete reverse of the truth. The ISA bus is
>totally isolated from pci (and the cpu), the AGP is not, it *is* a pci
device.

Actually, AGP resides on the memory bus side of the memory/cpu-to-PCI
bridge.  One of the 'advantages' being that AGP can access main memory at
the same speed as the CPU, using it to store 3D textures and such (before
VRAM, and RAM in general, came down so much in price that the point is
moot).  The other advantage being that AGP has a lot more bandwidth future
- it can stay at or ahead of the memory bus speed, unlike PCI, since AGP is
actually a port, not a bus (a two-way pipe with one destination at each
end, instead of having multiple devices communicating concurrently).  But
as you were saying, ISA resides on the ISA side of the PCI-to-ISA bridge,
and is quite seperate.

Regards,
Christopher


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