R740xd UPI links

Hey there,

the easiest way to find out the number of UPIs (possible 2 to 4) is to check it online at https://dell.to/2SaZEsu.

There are so many different CPUs that can be used with the R740xd that I'm not able to answer your question directly. If you know the name of the installed CPU then we can check it in detail.

Cheers
Stefan

The unit is Xeon 6252 with 3x UPI links.

I want to know if the motherboard in R740xd actually implements 3 UPI or not.

There are a lot of servers that actually use 2 UPI links even if the CPU supports 3x UPI.

Hi,

when I take a closer look at the system board diagram, it seems to be the same for this system.
There are just 2 links.

So it seems that this is the situation right now.

I found something that proves it: 

Internal interconnect:
Two Intel Ultra Path Interconnect (UPI) links, 10.5 GT/s
3UPI link capability is not supported on the PowerEdge 2-socket platforms (R440, R540, T640,
R640, R740, R740xd, C6420, M640, FC640) 

I guess this is your answer.

Regards
Stefan

Hey,

I guess with the next generation of servers it's possible to use more than 2 links. When the motherboard was designed there were just 2 links with QPI. UPI was invented/implemented later, so actually, there is no road where the traffic can flow ^^

Cheers
Stefan

I guess with Ice lake there would be 4 upi links with the SP units, like AMD is doing. And possibly they will bump the speed, just like they did from QPI to UPI

Not necessarily. We can also have 2 UPIs with 4P servers in a ring topology. (ofcourse that wont be optimal, but there are vendors who do that.)
for 2S nodes usually 3x UPI are not required unless we require a lot of I/O across devices.

Three UPI links are used for server with 4 Sockets (E.g. R840, R940 Etc.). As R740xd is 2 socket server only 2 UPI links are supported by motherboard

Thanks.
That clears it up.
Usually 3x UPI are used in high density GPU servers, where a lot of P2P access is required between GPUs.
Also this is one of the reasons why P2P is much faster with AMD rome.

Yes @elly_00  ring topology required only 2 UPI. As per my understanding Dell Power Edge server 4 socket server have cross bar configuration where 3 UPI links are utilized. 

I know that. It wasn't my point.