192 requires 2nd cpu Riser card and 4 Ram Riser cards and 4 ram riser power cables.  ram should all same speed same rank same vendor ddr3 1333

http://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_dell_precision_workstation/precision-t7500_service%20manual_en-us.pdf

192 is max because 16 gigs is max dimm size and there are 8 or 12 ram slots not 16.

When you use the Riser cards thats 8 slots.

The other 4 ram slots are on the 2nd CPU Riser Card.

The Ram Riser cards are 4 cards stacked back to back and have power cables going to them.

12 x 16 =192

And FYI, Precision Fixed Workstation forum

So I have a Dell T7500 with 96GB ram - 12x 8GB PC3 10600R (1333MHz).
I'd like to upgrade it to 192, but it gets a little confusing.

Pushing it requires 12x 16GB PC3 10600R (1333MHz) - they are quad rank.
OK, but there is a note in the manual:

"If more than one Quad rank DIMM is installed within a channel (DIMM1 & DIMM4, DIMM2 & DIMM5, DIMM3 & DIMM6) then the maximum DDR3 speed is reduced to 800 MHz. Spreading Quad Rank memory modules accross multiple channels is recommended."

What speed are they referring to?
Are we dropping from 1333MHz down to 800MHz? If so, that upgrade blows, we get twice the ram but half the speed
Maybe it's the single direction speed being capped at 800MHz. If so, the 1333MHz memory runs at 667MHz anyway so no biggie.

They suggest a solution, spreading the Quad modules to different channels, and there is a configuration in the table with 128GB - 4 of the 6 channels get a single 16GB module, everything else is populated with 8GB - yay
Except after that the table jumps straight to 192GB configuration. What about 144GB???
6x16GB +6x8GB - the quads are spread to all the channels, we get 144GB at full speed.
But why did they not mention this? Is 144GB not supported for some reason???

Also what is the whole deal with 192GB needing Red Hat?
Does windows not support it??

PS.

There is another idea - anyone tried putting PC3 32GB 4x4 10600R modules into T7500? Do they work?

This way I can reach 192GB using only 6 modules - no slowdown

192 requires 2nd cpu Riser card and 4 Ram Riser cards and 4 ram riser power cables.

ram should all same speed, rank , same vendor ddr3 1333

http://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_dell_precision_workstation/precision-t7500_service%20manual_en-us.pdf

192 is max because 16 gigs is max dimm size and there are 8 or 12 ram slots not 16.

When you use the Riser cards thats 8 slots.

The other 4 ram slots are on the 2nd CPU Riser Card.

The Ram Riser cards are 4 cards stacked back to back and have power cables going to them.

12 x 16 =192

Yes I have a riser and a total of 12 DIMMs.

Thanks, couldn't find it myself, kept ending up at a read only forum

I reposted there, so if anyone has the power to kill this thread, please do

Speedstep: like I said, my current configuration is 12x8GB.

I do have a riser, there are 6 dimms on the board and 6 on the riser, not sure what you mean by all the 4s in you post

2nd CPU Riser has 4 cards.  There are 4 Ram Risers Total  6 dimm slots.  6 slots with a 16 gig dimm and 12 slots with a 16 gig dimm = 192 total.  You cant put 6 riser cards in the motherboard you can only put 1 set of riser cards.

The T7500 is a Single Processor system with 6 Dimm Slots or a Dual Processor System with 12 DIMM slots if the optional expansion riser cards are installed. There are three memory channels, each managing two DIMM slots with three additional channels managing two DIMM slots if the riser is installed. You cannot use 16 dimm slots or all of the slots on the motherboard when the riser cards are in.  The 2nd CPU card DOES NOT HAVE 8 slots for ram.  The riser cards are not stand alone they have aux power cables that are proprietary.  You cannot use all 8 slots on the 1st cpu board with risers.

Dell Heatsink with Fan (Part: W567F)  G802W
Dell Memory Blower Fan (Part: Y730D)
Dell Memory Shroud (Part: P787F)
Dell 2nd CPU and Memory Riser Board for T7500 (Part: H236F)

Maximum Memory: 192GB

Slots: 12

Each memory slot can hold DDR3 PC3-10600, DDR3 PC3-8500, DDR3 PC3-12800 with a maximum of 24GB kit (8GBx3) per slot.*

Supported Memory Configurations

Single Processor Memory ConfigurationsSize(GB) DIMMRanks DIMM1 DIMM2 DIMM3 DIMM4 DIMM5 DIMM6

Dual Processor Memory ConfigurationsSize(GB) DIMMRanks MB DIMM1 MB DIMM2 MB DIMM3 MB DIMM4 MB DIMM5 MB DIMM6 Riser DIMM1 Riser DIMM2 Riser DIMM3 Riser DIMM4 Riser DIMM5 Riser DIMM6

Memory Slots

There are six memory slots on the system board. The slots are numbered DIMM1 through DIMM6. DIMM1 is furthest from the processor.

In addition, the dual-processor riser features six additional memory slots. The slots are numbered DIMM1 through DIMM6. DIMM1 is furthest from the processor.

Memory Population Rules

Your computer requires DIMMs within a channel to be populated starting with the DIMMs farthest from the processor first. This means the DIMM slots 1, 2 and 3 must be populated before DIMM slots 4, 5 and 6. In addition, when populating a Quad-rank DIMM with a Single- or Dual-rank DIMM in the same channel, the Quad-rank DIMM must be populated farthest from the CPU.

To maximize available memory bandwidth, DIMMs within a configuration should generally be spread across as many channels as possible before populating multiple DIMMs per channel. The population guidelines below help to achieve this.

Single CPU configurations (6 DIMM slots on MB)

• If configuration contains DIMMs of all the same size, populate in the following order: DIMM1, DIMM2, DIMM3, DIMM4, DIMM5, DIMM6
• If configuration contains DIMMs of mixed sizes, populate the larger DIMMs first. For example, for a 4GB configuration consisting of one 2GB DIMM and two 1GB DIMMs, the population would be DIMM1=2GB, DIMM2=1GB, DIMM3=1GB, DIMM4=empty, DIMM5=empty, DIMM6=empty.

Dual CPU configurations (6 DIMM slots on MB plus 6 DIMM slots on Riser)

• If configuration contains DIMMs of all the same size, populate in the following order: MB_DIMM1, Riser_DIMM1, MB_DIMM2, Riser_DIMM2, MB_DIMM3, Riser_DIMM3, MB_DIMM4, Riser_DIMM4, MB_DIMM5, Riser_DIMM5, MB_DIMM6, Riser_DIMM6.
• If configuration contains DIMMs of mixed sizes, populate the larger DIMMs in the dual-processor riser.

Dimms should be matched both Speed and Rank and vendor. Single and Dual Rank is supported.  QUAD RANK is not supported and mixing ranks is not supported.  Mixing vendors is not recommended unless you like trouble and blue screens and crashing.

The question keeps getting asked can I go over 192.

Answer No you cannot.

You have 6 slots with 1 cpu and 12 slots with 2 cpus and the associated cpu and RAM riser cards and power cables.

OK,

everyone, thank you for your help.

Please stop copying and pasting the manual for T7500.

I already described everything that is written there, it's just that not all information is in the manual.

It doesn't say if T7500 supports 144GB RAM the way it supports 128GB.

There is an issue of the speed drop while using 8ranks in total in a single channel.

A drop would be expected, but a drop from 1333 down to 800? Seems a little big, judging by the way other systems work in this scenario.

T7500 DOES support Quad rank modules, and mixing different rank modules is not only supported but actually advised

And there's also a question of supporting 32GB modules - if it does support them, they would pretty much solve all problems.

Obviously manual does not say it supports 32GB modules, because they didn't even exist when the manual was written.

So the question is if anyone here has ever tried putting 32GB modules into a T7500 or T5500