Intel xeon 600 workstation cpus and max memory speed

[jpmomo]

I thought that the new xeon 6 workstation cpus (698x, etc) were able to run at 8000MHz if using mrdimms. but I have noticed on the official intel site:


Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s)
MRDIMM(8000MT/s)
Maximum Memory Speed
6400 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes


This seems to show that they are limited to 6400MT/s. Most of the non-workstation cpus can at least go to 8000MHz when using 8800MHz mrdimms. I was expecting the workstation cpus to do a little better as they are "x" cpus.

 

[RolloZ170]

MRDIMM(8000MT/s)

e.g. 6781p supports 6400MT/s RDIMM, 8800MT/s MRDIMM
this 678x supports 6400MT/s RDIMM, 8000MT/s MRDIMM which i can't find (only 8800)

more sense would make
DDR5(6400MT/s)
MRDIMM(6400MT/s) <-- they can run 8800MT/s @ 6400
Maximum Memory Speed
6400 MT/s

in detail a 8800MT/s runs two ranks each 4400MT/s same time ( 2200Mhz QDR5 ) ( MRDIMM (Multiplexed Rank Dual Inline Memory Module) )

 

[jpmomo]

thanks.
the reason for some of my confusion is that I didn't look close enough at the spec (intel ark) where it said that the "X" series supported both 6400 and 8000 (not 8800 as most mrdimms). What also caused some confusion is that most of the 6 series supports 6400 and 8800 but the 8800 mrdimms only RUN at 8000.
I have a few 6 series ex. 6776p that I use the mrdimm 8800 but they are limited to 8000.
I also have a few 6979p which run the same mrdimms at 8800.
I was expecting the X series which should be overclockable to at least run at 8000.

In fact, there were several videos that showed the 698x running 8800 mrdimms at 9600! these were the same mrdimms that I use.

 

[RolloZ170]

I was expecting the X series which should be overclockable to at least run at 8000.

don't need to be OCed. because 8000 MRDIMM is 2000Mhz (quad data rate)

 

[jpmomo]

Why do they list the max speed as 6400?

 

[RolloZ170]

Why do they list the max speed as 6400?

8800 MRDIMM runs 2x 4400Mt
DRAM chips are normal 4800s.

 

[RolloZ170]

Why do they list the max speed as 6400?

if you have dual channel 4800, ram speed is still 4800 but 2x.

 

[jpmomo]

I understand that but if you look at the intel ark specs, they show max speed of 6400, not 8000 like I was expecting

 

[jpmomo]

And for the 6781p, they list 8000 as max speed

 

[RolloZ170]

I understand that but if you look at the intel ark specs, they show max speed of 6400, not 8000 like I was expecting

the RAM is 8800(2x 4400)
speed = 4400

 

[RolloZ170]

And for the 6781p, they list 8000 as max speed

the mem. controller can only 2000Mhz in MRDIMM mode not 2200Mhz.

 

[jpmomo]

That still doesn't explain why they list 6400 max speed for the 698x but 8000 for the 6781p

 

[RolloZ170]

That still doesn't explain why they list 6400 max speed for the 698x but 8000 for the 6781p

Intel people are confused, just like you.

 

[jpmomo]

So you are agreeing with me that the specs on intel ark are incorrect and it should say 8000 for max speed just like the 6781p?
The reason I am trying to get confirmation is the aggregate memory bandwidth is important for my AI workstation build and I want to ensure that if I switch to the 698x, I don't regress on memory bandwidth.
Thanks for persisting with this thread and helping as you always do

 

[RolloZ170]

So you are agreeing with me that the specs on intel ark are incorrect and it should say 8000 for max speed just like the 6781p?

no. max. speed 6400 is corrrect.
8800 MRDIMM is speed 2x 4400Mt

 

[jpmomo]

I understand how mrdimms work but that is not how they normally list the max speed. See below for what I am specifically asking for confirmation on:
(and btw, I have verified all of the below on my own systems (most of them thanks to a good friend ) except for the 698x that I am asking about.)


Intel 6781p:


Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s), MRDIMM(8800MT/s)
Maximum Memory Speed
8000 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes


Intel 698x:

Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s)
MRDIMM(8000MT/s)
Maximum Memory Speed
6400 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes


Intel 6979P:

Memory Specifications
Max Memory Size (dependent on memory type)
3 TB
Memory Types
DDR5(6400MT/s)
MRDIMM(8800MT/s)
Maximum Memory Speed
8800 MT/s
Max # of Memory Channels
12
ECC Memory Supported ‡
Yes


Intel 6776P:


Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s), MRDIMM(8800MT/s)
Maximum Memory Speed
8000 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes

 

[RolloZ170]

except for the 698x that I am asking about

HWinfo tells me
max. MRDIMM speed = unlimited

pls ask Intel, they answer you.

 

[RolloZ170]

except for the 698x that I am asking about.

my last try with your side of view:
if 698x only supports 6400Mt
the datasheet must look like this:

Intel 698x:

Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s)
MRDIMM(6400MT/s)
Maximum Memory Speed
6400 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes

yes i know i can't buy 6400Mt MRDIMM, same for 8000Mt.

 

[RolloZ170]

Intel 6781p:


Memory Specifications
Max Memory Size (dependent on memory type)
4 TB
Memory Types
DDR5(6400MT/s), MRDIMM(8800MT/s)
Maximum Memory Speed
8000 MT/s
Max # of Memory Channels
8
ECC Memory Supported ‡
Yes

Intel Xeon 6700P is planned to support 1DPC 8000 MT/s RDIMM functionality on select SKUs,

Memory Bandwidth May Be the Most Overlooked AI Performance Metric

Intel Xeon first to market with 8000 MT/s RDIMM support underscores why data movement is becoming a competitive differentiator.

newsroom.intel.com

 

[sbert]

Sucks because at least on eBay, used DDR5 8800 MRDIMMs are a lot cheaper than DDR5 5600 RDIMMs, but DDR5 8000 MRDIMMs are nowhere to be found. Too bad you need at least a $11k+ 6700P processor and DC compatible granite rapids motherboard to run them, and unlike with RDIMMs, a DDR5 8800 MRDIMM apparently can't just drop down to slower DDR5 8000 speeds.