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

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

Hi

Irek Defee wrote:
> I mean you can send from a device to the network 400 Mb/s. I am not
> based on speculation here.
So 400 in and 400 out plus overhead. That's 75% efficiency and not too bad.
I think the DVB adapters are limited to around 45Mbps per transponder so 6
cards of 45Mbps is only 270Mbps give or take some.


> We were doing in the past experiments in
> transferring data form disk arrays and RAMdisk to Gigabit Ethernet
> network. This number was obtained for 32bit/33MHz PCI bus, different
> transfer modes were not significant factor.
The actual network adapter may influence the overhead, but lets
assume you used the best available.

> > One other thing, the PCI bus is no longer the only mean of transfer
> > data externally...........
> This is true, there are more advanced architectures which could 
> provide more output. Even going to faster PCI buses: 66 MHz doubles 
> the throughput and 64-bit doubles it again.
True and it will be interesting to see how well new GE-cards
will be connected into the CPU/Memory through this new serial
PCI bus (is it PCI-extended or PCI-express or PCI-X ? Anyway
the new serial PCI bus). Watch out for new boards.

> > 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.
> It is strange that this issue has been downgraded comparing to kernel
> 2.4. For me it’s a huge factor not to upgrade to 2.6:).
To me it was necessary to go to 2.6 due to SATA support and needed
bugfixes in the GE-adapter drivers not available for 2.4

> But I would suggest to developers to  take this into account and provide
> direct plug-and-play support for more than 4 cards. 6 PCI slots is the
> maximum amount in PC motherboards which also have on-board network
> adapter. Thus, it is natural to think that high-end installations
> may include 6 cards. Then, there are also more exotic server boards
> with several PCI buses and they could take more than 6 cards which
> could also be considered.
I concur.

--PMM