[mythtv-users] EPIA fan noise ?

[Maarten]

On Monday 02 August 2004 23:59, Gert van der Knokke wrote:
> Maarten wrote:
> >On Monday 02 August 2004 18:59, Stephen Tait wrote:
> >>At 17:47 02/08/2004 +0100, you wrote:


> >In any case, a PCI riser card 'rises' only one PCI slot.  You cannot put a
> >two-slot risercard in one slot and expect both slots to work then. PCI
> > isn't designed that way.
>
> Erm, yes it is, all PCI slots share the same data and address lines,
> it's a bus remember.

Sorry but you're wrong.  Read the PCI-SIG specifications.
"It's a bus remember".  Sigh. Not all buses are alike, and not all slots on a 
bus automatically have the same connections.

http://www.techfest.com/hardware/bus/pci.htm

I'll quote you some excerpts:

"Initiators arbitrate for ownership of the bus by asserting a REQ# signal to a 
central arbiter. The arbiter grants ownership of the bus by asserting the 
GNT# signal. REQ# and GNT# are unique on a per slot basis allowing the 
arbiter to implement a bus fairness algorithm."

and

REQ#	    Request is used by a PCI device to request use of the bus. Each PCI 
device has its own unique REQ# signal.

GNT#	    Grant indicates that a PCI device's request to use the bus has been 
granted. Each PCI device has its own unique GNT# signal from the PCI system 
arbiter.

> The IRQ's are usually connected in a round robin way, IRQ A is IRQ B on
> the second slot and IRQ C on the third etc. A PCI card normally takes up
> the first IRQ but can take second, third or fourth. All PCI cards should
> be able to share IRQ's but some are more well behaved than others...

The fact that there are 4 separate IRQ lines (INTA#, INTB#, INTC#, INTD#) does 
nothing to permit more than one card per slot, as the INT lines have nothing 
to do with the bus arbitration.

> There are lots of proprietary motherboards around which have only one
> PCI slot with a riser to create 2, 3 or 4 horizontal PCI slots. (Low
> profile Compaqs, HPs etc.)

Yes. And those invariably have a proprietary slot onboard where the risercard 
fits in. NOT a PCI slot.

Maarten

-- 
Linux: Because rebooting is for adding hardware.