Z420 RAM upgrade compatibility and performance concerns

[khorkhov]

I have a Z420 (spec) with a Xeon E5-1650 3.2GHz processor.  This system has 8 DIMM slots with 4 channels per CPU.

From what I understand, I must use ECC unbuffered DDR3-1600MHz memory for this system and CPU.  I currently have 16GB (8x2GB) and plan to upgrade to 32GB (8x4GB or 4x8GB).  The currently installed 2GB DIMMs are 

1Rx8 PC3L-12800E (DDR3-1600) Unbuffered CAS-11 Low Voltage.

Compatilbity questions:

• Is the new memory required to be "low voltage" like the old one?
• If I go with 8x4GB DIMMs, is it recommended that I buy a kit that comes with 8 DIMMs or is it the same to just buy 4 2x4GB kits.  (I was under the impression that it's the same but this forum post claims otherwise)

When searching HP for server memory (search query), I found two ECC 4GB 1600MHz UDIMMs: 2Rx8 CAS-11 Low Voltage, and 2Rx8 CAS-11.  Both of them are $79.

However, when searching HP for workstation memory (search query), I found the following ECC 4GB 1600MHz UDIMM: A2Z48AA.  This is $160 and doesn't mention the number of ranks or CAS latency.

The workstation memory seems to twice as expensive.  Does anyone know how it's different?  Is it single rank vs dual rank for "server memories"?

Performance questions:

• For maximum performance, do I need 8x4GB or would 4x8GB achieve the same performance.
• In the 4 DIMM configuration, since I'm putting one DIMM  in each channel, would 4 dual rank DIMMs be preferred to 4 single rank DIMMs?
• In the 8 DIMM configuration, would 8 single rank DIMMs be faster than 8 dual rank DIMMs?
• In my searches above, I only found CAS-11 "server memories" and the "workstation memory" doesn't mention CAS latency.  Do any CAS-9 memories exist for my system, and is there any noticable performance difference between CAS-11 and CAS-9?

Thank you for your help

[Stefan_Kühn]

Newer Rams such as Kingston automatically support the CAS latency and they automatically adjust to the right specs and speed.

You may go to the kingston side and select your RAM.

On older workstations such as the XW4000 to the XW8000 this was critical due to the fact that the chips had a slighty higher heat development when running a longer time which resulted in unreliable operation during hard tasks.

Non of this problems should occur with those workstation when using third party memory.

[Dan_WGBU]

Here are some memory performance hints for the Z420. 

The Z420 (Z620, Z820) have 4 memory channels per CPU, and each channel has 2 DIMM sockets:  one black, and one white.  Maximum performance is achieved when there is identical memory modules are installed in each channel, because memory can be accessed on all channels at the same time (OK, that is a very oversimplification). 

To get the highest performance, install 4 of the same type of memory modules in each channel (put one in each black DIMM socket). 

If one wants more memory, then put 4 identical modules in the white  DIMM sockets.

Dual rank memory modules can typically give 15% to 20% more performance than single rank memory. 

There are exceptions to this, but these are general memory population rules.

Workstation memory is ECC, and most are registered memory.  These added chips increase memory cost. 

I cannot recommend third party memory, nor do I even know what third party memory is compatible (or reliable).  

The system will work with different size DIMMs in each channel, but will not give the maximum memory bandwidth.  Of course, there are configurations that will not boot, such as mixing ECC and non-ECC memory, and mixing registered and unbuffered memory. 

HP has a Z420 memory configurations and optimization white paper, here.  This explains memory configurations better than I can.

[fickle_fred]

i installed 2 different types of RAM. One was 8 gig with no luck. The unit would go into turbo fan mode and sit there, no video, no power to keyboard. Took the stick out, works fine with current ram. Tried again today with 2 4gig sticks. same thing. Z420 goes into turbo fan mode with no video etc. I have tried them in many different positons according to HP specs. 

Where can I find RAM that will work??

[Zak-Smith]

I have booted a z420 (e5-1620 "v1") with 16 GB RDIMMs-- that's right, registered.  HP # 672309-581

This leaves me wondering why all the QuickSpecs for the z420 specify unbuffered memory only.

[AESystems]

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@Zak-Smith wrote:

I have booted a z420 (e5-1620 "v1") with 16 GB RDIMMs-- that's right, registered.  HP # 672309-581

This leaves me wondering why all the QuickSpecs for the z420 specify unbuffered memory only.

---

Simple really. The C602 chipset doesn't limit the memory. The CPU supports all types (remember memory controllers are built into the CPU)

The limitation is built in by the motherboard maker. Why? It's a workstation class motherboard, they want you to pay more for a "server" to utilize registered memory and gain more slots.   

I wouldn't be suprised if more memory works, I'll be testing some soon.

 The real question is can you surpass the supposed 64GB limit by using those 16GB RDIMMS. 

[AESystems]

Welp, I just tested it. RDIMMS do work. 

I pulled Dell branded Micron memory from a T7500. 

These are DDR3 1.5V 1333mhz rdimms.

They didn't just boot

HP memory diagnostics Passed

Windows Memory Diagnostics Passed

Memtest 86+ Passed

Just keep in mind, it's an unsupported configuration. 

[Zak-Smith]

After the warranty period, it's ALL unsupported.

And now HP cuts us out from maintenance firmware updates, which is seriously weak.

[joselso]

Please explain how HP cuts out Z-series workstations users from firmware updates after the warranty period.

I have just now downloaded such an update for my 3.5-years old Z820.

[Zak-Smith]

LOL @ posting a "Let me google that for you" link being censored.

Anyway, you can google for "hp announcement warranty required to download firmware" for what I was referring to.

Here's one link, https://community.spiceworks.com/topic/439491-hp-proliant-server-out-of-support-warranty-grab-firmwa...