HP z640 Memory Configuration

[ryan4780]

Hello all.  I am running a z640 which currently has 4x4gb memory installed.  I am thinking of adding the 2nd CPU Riser card and adding additional memory, so my question is two-fold. 

1) If I just add additional ram, do I have to replace all 4 sticks of RAM or can I remove stick 1 and upgrade it to an 8gb stick?

2) If I add the 2nd CPU Riser card, do I have to have identical sticks in that one (4x4gb) or could I have slots 1 (for CPU0) and slot 2 (for CPU1) populated with 8gb sticks and then have the 4gb sticks in slots 3-6?

From what I have read, both of these configurations should work fine but I wanted to confirm.

Thanks a bunch!!!

[banhien]

@ryan4780 

Please read from page 19 of the following Guide

            https://www.bhphotovideo.com/lit_files/113007.pdf

Regards.

[ryan4780]

Yeah, the same thing is in the HP Z640 Service manual.   But it doesn't clarify if Dimms of different sizes are Okay.  I assumed they were since there are 4 channels per CPU, 1 socket per channel.  But before spending the money to buy it I wanted to confirm.  So, would you say both of those are a "yes" or a "no"?

[banhien]

@ryan4780 

You can work by the book or try yourself at your own risk

Regards.

[ryan4780]

Or I can ask if anyone else has tried something similar and what their results were.

If only there were a place online to post those kinds of questions. You know, a place where people who also use the same product come to ask questions too and maybe answer someone else's. Oh wait.....

[DGroves]

if you install the sec cpu riser board then you "MUST" also install the sec cpu into the riser board before the ram slots on the riser board will work

each cpu has it's own specific group of memory slots

The single processor Z640 has 4 DIMM Slots supporting up to 512GB DDR4 ECC Memory.
The dual processor Z640 has 8 DIMM Slots supporting up to 1TB DDR4 ECC Memory.

in regards to memory/dimm banks look at the HP z 640/z620 memory table and you will see that yes you can use different memory modules as long as each bank is comprised of the same 2 memory size dimms

to use DIMMs of different sizes, load them in order of size, starting with largest and finishing

with the smallest (largest in DIMM 1, smallest in last loaded DIMM slot)

https://www.manualslib.com/manual/899901/Hp-Z440-Workstation-Series.html?page=77

[ryan4780]

I'm sorry but you blew right past the root of my question.   What do you mean by: "each bank is comprised of the same 2 memory size dimms"?    Do you mean that slot 1 of  CPU0 (actual slot 1) and slot 1 for CPU1 (actual slot 2) have to match each other?  Or am I completely missing your meaning?   I'm just not following you.  How can you have both the same and different size memory dimms at the same time?  Two dimms either are the same size or different size. They can't be both at the same time, can they?  LOL

And I'm really not trying to be an ass, I genuinely am just not understanding.  I'm sorry.  I really appreciate your help.

[DGroves]

i don't usually answer questions that have answers in numerous places such as the HP user manual/service manual and quickspecs (and quite a few google links). but for some reason people seem unable to locate them or understand them so i'll try to repeat what they say in perhaps a more understandable format

The HP Z640 Workstation is a Dual Processor capable system with 4 DIMM slots per CPU.

the dimm slot load order will change depending on if you have the sec cpu riser board installed

There are two memory channels per CPU, meaning Each memory channel manages two DIMM slots

each memory channel should have the same size/speed dimm for the best results but it is possible to have two 32gb dimms in one mem chanel and two 64gb dimms in the other memory chanel (single cpu config)

for a dual cpu system you need to duplicate the same ram config again for the second cpu's 4 dimm slots

if you install mismatched ram in the memory channels for either a single or dual cpu config  then the system will either run in single channel mode which will cripple performance or not boot at all and give a memory error

The installed CPUs determine the speed at which the memory runs. If an 1866MHz capable CPU is used in the system, the maximum speed the memory will run at is 1866MHz, regardless of the specified speed of the memory.

ONLY registered and load reduced DDR4 DIMMs are supported. DDR3 DIMMs ARE NOT SUPPORTED.

again please see the HP quickspecs (memory section) for some of the HP approved memory configurations

https://www.dectrader.com/docs/set06/492792/c04400040.html

[ryan4780 · Accepted solution]

You know what, you are being a real jerk and being completely unhelpful.  None of that answered the direct question that I asked.  All I was looking for was a simple yes or no.  

If you took the time to actually read my question, you would have seen that the information that I was seeking is not answered in the spec.   In fact, I have read the service manual cover to cover.  

Why would you take the time to come on a forum to answer a question only to NOT answer the question and be insulting?  

By the way, I have unsubscribed from this thread and will never come back to this forum to ask a question again.  Thank you for confirming that I should have never bothered asking in the first place.