X-video-server [Open-graphics]

[James Richard Tyrer]

Dieter wrote:
>> no, it´s not the problem to have Eth ports on the PC side, as you notice
>> yourself _Dieter_ even low-end PC privide one port.
>> Rather, a chip on the PC´s mobo which route the PCI signal through
>> Ethernet.
>> (and on the monitor g-card, the contrary, though it could be not
>> necessarly to bother with a PCI slot, as you suggest)
> 
> Oh!  I think I *finally* understand what you want.  A PCI slot extender that
> uses Ethernet for the link.  Interesting idea.  I don't know of such a
> device.  Anyone?  The closest thing to this that I know of is a device
> for adding more PCI slots or adding PCI slots to laptops.  It looks like the
> cable is limited to 1.5 meters.  It is also expensive.  For most purposes one
> might as well buy an additional computer instead.
> 
> http://www.mycableshop.com/sku/PCI-P7T.htm
> 
> It might be that the PCI bus has timing/latency requirements that prevent
> a remote slot over a long cable?

Some time ago, AMD sold a chip to extend a parallel bus over coax, so 
this is clearly possible (depending on the bus clock frequency -- IIRC, 
this used ECL to drive the coax :-().  The largest problem with a 
hardware extender would the clock sync.  If the remote PCI card wasn't a 
bus master, it would just be slow to respond -- limiting the clock 
frequency or wire length.  But, with a bus master on the remote end, 
there needs to be some interaction and the delay of the wire would limit 
its length.  So, you would probably wind up with a software driver that 
would wait for the remote PCI card to respond.  This is going to slow 
things down considerably.  I can't see this being near as fast as 
running an X server over the same speed wire.

OTOH, a remote X server that uses a plug in graphics card is something 
to consider.

But, I see no upside to this.  You need two cards and 2 connectors -- 
that can only increase the cost.  You have two cards closely spaced 
creating cooling issues and memory socketing issues.  The X server and 
the graphics system would need separate memory chips and controller -- 
more cost.

And what are the advantages over a single card?  You could upgrade the 
graphics hardware without replacing the X server.  There might be a 
slight increase in speed by using separate memory spaces for the X 
server and the graphics, but it that matters you could do it on a single 
card.

The only product placement I see for this would be an X server being 
sold to use existing graphics cards.  Something that we probably 
wouldn't be doing since we would be right back to the same problem with 
drivers and lack of open hardware.

-- 
JRT