[linux-dvb] Re: More than 4 DVB cards - again

[Peter Maersk-Moller <peter@maersk-moller.net>]

Irek Defee wrote:
> > > Another issue though is how 
> > > much stream juice one can squeeze out of the cards at the same
> time...
> > I don't see why you can't squeeze 6*45Mbps = 270bps over the PCI bus
6*45Mbps = 270bps should have been 270Mbps of course.

> > and the same amount when you send it to a network card. AFAIK, you
> > can transmit 1056Mbps at most over the standard PCI bus (32bit 33MHz).
> 1056 is theoretical number. Normally you need to read from the card
> and write to network adapter, so it is twice less. In practice it will
> be around 400Mbs.
You mean in practice you can expect to transmit a maximum of 2x400Mbps
over the PCI bus ? it will of course depends on the way the PCI bus
is used. There are many modes of transfer over the bus.

One other thing, the PCI bus is no longer the only mean of transfer
data externally. I'm using HS USB2.0 ports to off-load data onto
encoder machines. On some motherboards the on-board usb chip
shares the bandwidth limitation of the PCI-bus, on some they
DON'T. Furthermore, there are motherboards with network adapters
and other adapters included in the North-bridge with direct access
to RAM instead of connected through the south-bridge. There
are also motherboards with mor ethan one PCI-bus.

Otherwise you are correct, streaming more than 400Mbps from
a single PC is not trivial.

> I am streaming about 130 Mb/s from machines with 6 cards but they run
> 1.3 GHz Celeron processor which is then fully loaded. Tests would need 
> to be done on 3 GHz Pentium 4 to see how much can be pumped then.
I have one here with 5 slots, but I have a problem getting more than
4 receivers as mentioned in the beginning of the thread.

--PMM