On Fri, 25 May 2018 18:01:47 +0100, Jimmy Wilkinson Knife wrote:

On Fri, 25 May 2018 17:34:43 +0100, Paul wrote:

Jimmy Wilkinson Knife wrote:
PCI express graphics in a 1 lane slot? Yes I know I can fiddle with
extension ribbons, but why have they designed the 1 lane slots to
physically not allow longer card to go into them? Is it to stop the
user squashing motherboard components which may be nearby? Obviously it
would run slower, but that depends on what you're using the card for.
Only games need fast data transfer rates. If you're going to use the
extra cards for more displays, scientific computing, or bitcoin mining,
thy just don't need more than 1 lane, as evidenced by the plethora of
adapters available. Hell you can even split a single lane socket into 4!

They make connectors which are open on one end, and allow
cards larger than x1 to fit in an x1 slot.

https://en.wikipedia.org/wiki/File:P...d_IMG_1820.JPG

MSI had some motherboards with x4 slots that did this.
The slot was yellow in color. Likely the same color as the
one in that picture.

That would be useful. Better to have a card that's not quite tight than one that won't fit. And I don't fancy sawing off part of a connector while it's on the board! I'll stick to using adapters and extension ribbons.

What particularly interests me is something I saw on Ebay from China which claims to connect to an x1 slot and produce four x1 slots. Can you actually multiplex these things? I thought a lane was a lane.
This suggests you can, just like with a network switch:
https://superuser.com/questions/8949...google_rich_qa
I wonder how many GPUs could work at once - giving them the physical space and the PCI express connectors isn't a problem with those extensions and adapters, but I wonder if the drivers would get confused, or Windows, or I'd run out of BIOS address space? The most I can find is a bitcoin mining rig with 19 cards, and a special motherboard by Asus I think.

Just done a calculation. I could run 35 Radeon HD 7970 cards on an i7-8700K before I ran out of CPU power to assist them on Einstein@Home. I can't find anything on address space though. Does every device nowadays just get mapped to main memory? We don't have limits on interrupts and stuff nowadays do we?

--
The reason people sweat is so that they won't catch fire when having sex.