Re: [pci] Parallel PCI Communication Queries

["David Warren" <dave@luscher.co.uk>]

-----Original Message-----
From: sonicshaheen@hotmail.com <sonicshaheen@hotmail.com>
To: pci@opencores.org <pci@opencores.org>
Date: 18 May 2002 10:54
Subject: [pci] Parallel PCI Communication Queries


>Hi,
>
>    I am working on a system which has folloing hardware and network
>
>Hardware
> - Each PC is equipped with 2 PCI Parallel (32 bits) communication cards.
> - Both PCI cards can transmit and receive data.
> - 3 PCs are used
>
>Network
> - out of 3 PCs, 1 is Master and other 2 are slaves
> - Now as All PCs have 2 PCI cards(our designed cards) in them, All PCs
>are connected in a closed cascade, that is 1st PCI card of PC 'A' is
>connected with 1st PCI card of PC 'B', 2nd PCI card of PC 'B' is
>connected with 1st PCI card of PC 'C' and similarly 2nd PCI card of PC 'C'
>is connected with 2nd PCI card of PC 'A'.
>
>
>   Now the Question i have are
>
>1) If I send data from Master to PC 'A', how much data rate will i get? (i
>am expecting 132MBytes/s for PCI v2.1)?

I have some experence with PCI cards, mainly SCSI cards. Using a PC program
to do transfers to a PCI card target (read or write) is not very fast. To
get good performance on PCI the card needs to be a master and to do long
bursts on the PCI bus. You will never get 132 Mbytes/sec, but 40 Mbytes/sec
is possible.

>2) Do PCI slots share same PCI bus

Yes,  - (server motherboards may have PCI to PCI bridge as a way to get more
slots)

>3) If same PCI bus is used, Is it possible that if PCI card 1 in PC 'A'
>receives data, then due to common PCI bus, PCI card 2 of PC 'A' gets
>that data and place eletrical signals on PCI card 1 of PC 'B'?
>4) ANother way to look at above Qs is that if PCI cards share same PCI
>bus then at an instant both PCI cards have same eletrical signal and due
>to the interconnection whole network will have same eletrical signals. Is
>it possible?

With the FIFO's buffering the data in the PCI bridges (look at opencore PCI
bridge design) then no, same data is not on each PCI bus at the same time.
(PCI has long latency, another reason why you need long bursts for
performance)

>5) How do i transfer data from PCI card 1 of PC 'A' to PCI card 2 of
>PC 'A' using minimal clock cycles?

PCI card 1 can be master and PCI card can be slave, then transfer does not
go through system RAM.

>6) Is there any flaw in the network architecture or any impossibility in
>hardware design?

You would get better performance with a Gigabit ethernet card in each PC
connected to a Gigabit hub.

If you really want to link the PCI busses together the PLX sells a chip set
to do this.

>
>These are Questions coming thru my mind right now. If anybody out
>there has some answers plz  reply coz i despreatly need help right now.
>
>Thanx
>
>Bye
>
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