[ale] sorta [OT] IO vs clock cycles

[Mike Panetta]

Um, just to correct your post, PCI is 32 Bits and 64Bits, not 16 bits. 
It was never 16 bits.  ISA on the other hand is 16Bits.  And I think MCA
is too but I am not sure.

And with PCI its more complex then just how many bytes can you transfer
per bus clock.  First of all PCI multiplexes the address and data
together, so (and I may be incorrect here) the very first transfer on
the PCI bus is the address xfer.  After that you can do up to (I think)
512 data xfers (or whatever a cache line is on your CPU).  IE PCI
supports bursting, and you actually need to use it to get the full
bandwidth out of it.

Mike

On Fri, 2002-11-08 at 20:03, Larry Grenevitch wrote:
> To reply to the mainframe question.
> CPU speed is only one factor.  Several years ago I worked in a shop that sold 
> both AIX and SCO Unix boxes.  A 2 year old AIX box still beat out the latest 
> PC with on cache boards etc..  Why, IO, most PC boards are 16 bit with PCI 
> there is now 64 bit boards, on AIX and I am sure the mainframes you have 512 
> bit IO boards.  Or to put it another way, when your PC has gotten 16 bits [2 
> bytes of information] your mainframe transfered 512 bits or 64 bytes of 
> information.  And it is things like that all through out the system from IO 
> to memory.  That is why PCs are not really scallable, they just don't have 
> the base engineering.
> 



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