Z4 G4 memory upgrade: heat issues vs. module sizes?

[wny2016]

Just got an off-lease Z4 G4, came with 16GB factory RAM = 2 x 8GB modules. Oddly enough, this machine also has the HP memory fan cooling assembly installed, so as I understand it, I am free to use up as many of the 8 memory sockets as I need. I was thinking of just getting 4 x 8GB modules, as I have a source for the HP parts (Hynix memory). That would fill up 6 of the 8 sockets.

If I just got 2 x 16GB modules, there would be 2 fewer sockets occupied. Since I've got the cooling fans, I guess it really doesn't make much difference as to how the total RAM is configured, but I was wondering if there is any kind of heat tradeoff of the 8GB modules vs the 16GB modules. The machine has a high end video card and the front fan assembly as well.

[SDH]

Do you know the exact type of processor you have? If Xeon the memory is different than the Core memory.

You know the max memory speed your processor can run? You'd like to have your memory at least up to that speed. A slower processor will slow the memory down to its slow speed. Slow memory will slow a faster processor down to its speed.

Ideally you'd fill all black sockets with 4 identical sticks. If you only really need 32GB I'd start with just 4, assuming they're identical to your current two sticks. Do you current 2 sticks have HP labels with the HP Assembly P/N showing? If so what is that? Send a pic...

Memory matching is very important. Ideally you'd take a good pic of what came with your workstation... just 1 pic would be fine if they are identical. Plus a pic of what you'd add if available. Having mismatched memory is a major issue depending on the type of mismatch.

It never hurts to have that memory cooling saddle in place for any HP workstation even if it does not truly need it. Some boosts in memory amount will result in the motherboard demanding that plus a front lower case cooling fan in a black plastic holder.

Edit: I see you have that... good. The workstation may have had more memory from the factory before it was sold. Also, it does make a difference regarding which memory sockets are filled. Read up on the benefits of quad channel memory configurations. It is a synergistic benefit you can get in these workstations, and it is worthwhile to get that.

[wny2016]

Thanks, but it's just the relative heat produced by a 8GB module vs a 16GB module, that's all I was asking. The standard HP 8GB module for G4 Xeon 22xx machines is HP P/N L15415-501, which is actually  SK Hynix HMA81GR7CJR8N. Both numbers appear on the modules themselves on 2 different labels. I was just going to get 4 more identical modules, which results in a total of 6 of the available 8 memory sockets being occupied. I think that in order to get the full benefits of quad-channel, you have to install in sets of either 4 or 8 DIMMs.

Whenever I set up a HP workstation, and have to add memory, I just get more of what's already installed, pretty much. Depending on the machine the actual hardware can come from different vendors, as I don't think HP manufactures server memory at all. As I recall, some past machines, maybe Z440s, had HP memory that was actually Samsung.

[SDH · Accepted solution]

"I guess it really doesn't make much difference as to how the total RAM is configured."

It does make a significant difference...

 "I was wondering if there is any kind of heat tradeoff of the 8GB modules vs the 16GB modules."

There is... you lose quad channel benefit if you use two 16GB modules instead of four 8GB modules (even if the heat produced was the same).

Here's 3 different OEM vendors HP uses for the HP P/N L15415-501, all excellent and equally fast. If you want more than 32GB I'd recommend springing for 8 x 8GB rather than 6 x 8GB so all your memory is running quad channel. About 15.00 - 17.00 each today on eBay sorted by lowest price plus shipping. Good stuff...

[wny2016]

Thank you - very helpful! I'm going to take your advice and just fill up the slots with the 8GB modules. It will be interesting to see if I can discern any kind of practical speed improvement, although I am just starting to set up this machine. I'm going to put in 2 x NvMe RAID1 drives (motherboard slots) for the Win 11 system as well.

[SDH]

Wny2016,

Good news. Your chosen memory will go as fast as the Z4G4 memory and motherboard can ever run, and I do notice a benefit from all sticks being the same and running each bank in Quad Channel mode. In the technical and service guide you can see a diagram showing the two on-motherboard M.2 sockets port directly into your Xeon processor (ideal, vs into the PCH). Of interest, the PCIe3 x8 slot does too. There is a HP Z Turbo Drive Dual Pro (v1, and a newer v2) which can be inserted into the x8 PCIe slot. I found here that the ZTD DP in that slot left at BIOS defaults will bifurcate automatically. For the Zx40 workstations you instead need to set bifurcation to x4x4 manually rather than leaving it at the "Auto" default.

That card gives you two added x4 lane PCIe3 pathways directly into the processor to run two more M.2 NVMe sticks. I have both the v1 and the v2 of that... v1 is excellent and no benefit from the v2 for these workstations. Price on eBay is very good for the v1 brand new from HP via the Alan guys.  It would be interesting to hear what you would do with 4 M.2 sticks running in parallel in RAID that way...

[wny2016]

Hmm. Here's a question, then. I use the ZROCSTANMOD dongle to activate the bootable NvMe M.2 feature for the motherboard slots. The RAID1 configuration is handled through the Intel software. What this creates is a bootable C:/ volume that consists, typically, of 2 x M.2 NvMe 1TB drives for the system.

I don't think the Intel RAID controller will allow you to create a different Volume with additional drives contained in the Z Turbo card. By "different volume," I mean what would be another logical drive, say, E:/ to be used just for data. I usually create the bootable RAID as described, and then put in a cheap SAS/SATA RAID controller for 2 x 2.5" SSD drives that occupy caddies in the regular Z4 drive cage.

[SDH]

Never had to use a ZROCSTANMOD dongle to boot from the primary on-motherboard M.2 socket using a NVMe M.2 drive in my Xeon Z4 G4. That is the upper lower of the two there. Can't find that dongle using Google. 

I must admit that I don't use RAID, and I'm stuck right now on getting my PCIe plasmaholographic cables to work.

[wny2016]

Oops. Typo: VROCSTANMOD  This dongle is available in HP-branded versions, which are identical, but cost 2x as much. If you install the Intel IAStorUI  = Intel Virtual RAID on CPU software on your Z4, it will allow you to set up RAID volumes for the motherboard NvMe drives - but - they will not work as a bootable volume unless you install the dongle. There is a 30-day "trial" period that will allow the bootable RAID volume to work, but without the dongle, it goes away after that period has elapsed.

The whole idea behind the bootable RAID is just to keep a potential drive failure from necessitating some sort of system restore from backup, etc. Replacing a M.2 NvME stick is pretty simple if one should fail.