Single vs Dual Ranks, Memory Channels...

[JustinH]

Hi All,
So Im confusing myself and thought I'd post here for some clarifications.

I'm considering getting a Intel H2216 chassis, and looking at Memory options. This is for E5 v2 CPU's, and each sled comes with 16 Dimm Slots. (two CPUs, four Channels/CPU, and two DIMMs/Channel)

Now I've been reading up on memory for this, but I'm stuck on my best options.

1) I've read that when you have multiple DIMMs per channel, you effectively increase the Memory Rank that the system sees (so if you populate with Dual Rank, then the system sees it as Quad Rank per Channel)
2) Quad Rank usually results in a drop in memory frequency(?)

So, question is, how does it actually work and should I consider Single Rank memory if I want to populate all 16 DIMM slots?

 

[Stanza]

This is a bit of a rough explanation......but

=======

Depends... Most Boards ( or CPU if the memory controller is on the CPU) can only handle a certain amount of RANKS

eg think of it this way

Your board / CPU can say handle a max of 24 RANKS

Thats
24 x Single Ranks
12 x Dual Ranks
6 x Quad Ranks

Some can mix n match the ranks between the slots

eg 2 x Quad Ranks and 2 x Single Ranks

The above RANK limitation can also be PER MEMORY Channel.......which can be a gotcha tho

some systems are 2 x memory modules per channel
some are 3 x memory modules per channel

so in that case a manual that states it supports QUAD rank memory (Per Channel) would mean you could place
2 x single rank memory modules
or
2 x Dual Rank memory modules

in it, but
2 quad rank memory modules would break the bank.....(excuse the pun) as both modules combined ( a Channel ) would equal eight ranks.....

 

[JustinH]

Ok. So according to http://download.intel.com/support/motherboards/server/sb/g44057008_s2600wp_tps_r1_72.pdf#page28 the board supports upto 8 ranks per channel, so Quad Rank should work.

But any performance impact then?

 

[Stanza]

Ok. So according to http://download.intel.com/support/motherboards/server/sb/g44057008_s2600wp_tps_r1_72.pdf#page28 the board supports upto 8 ranks per channel, so Quad Rank should work.

But any performance impact then?

that I dont know sorry