choza wrote:squeen wrote:I heard SGI is going PCIx for the next generation of graphics which is suppose to be a higher bandwidth bus (\me = not really knowing what I'm talking about, all PC heritage stuff is terra incongita to me).
i though PCI-x was left instead of PCI express (by major cards manufacturers) because of cost, there was a roadmap for PCI-x to add MHz to the thing (standards were 33/66/133 Mhz if i remember) higher bus speeds were the next ones, but that demanded more cost on the construction, one reason the path of the clock and other stuff (if you look at every pci card you will find a "snake" path, thats the clock one, from the socket to the clock pin there must be about 2.5 in but not sure the std distance)
PCI express works different, its more like a LAN, one of its benefits: allows higher speeds easier
strange SGI not using pci express
it's highly unlikely they are using PCI-x, this 'standard' is long gone. next up (for everyone regardless of PC or not, it's matter of custom protocol or not. definately not worth a custom protocol such as numalink use case is) is PXI-express, which as choza intimates is different. the protocol uses SERDES (serializer/deserializer) to transfer data. the clock for SERDES is generally encoded with the data (or 'clock endcoded data') which means there is no seperate clock line at the PHY level. the data rate is (2.5gigabits/line)*(8b/10b) FDX for each 1X of the data width. common widths are 1X, 4X, 8X, and 16X (for graphics). so, you can move a lot of data pretty quick.