Will be interested to hear your thoughts on the P920 since you have the z600 and z620. I love my z600 as well--nice quite desk side server.
EDIT: Lenovo Performance Tuner
EDIT: typos/wording, and lack of block diagram.
Sure.
I never thought about getting a Lenovo workstation as I've been using HP's Z series for so long. The Z600 and Z620 were acquired new and they have been on practically 24x7 without any significant issue. Although I once purchased a 2nd CPU for the Z620 on eBay but it didn't work. So I'm unsure if it's because of the motherboard or the CPU. My Z620 never came with the special back plate that slotted into the 2nd CPU carrier. I am disappointed the Z620 doesn't have a physical second socket while the Z600 does. I thought about getting the Z640 but HP reduced the internal 3.5" drive bays back to two, the same as the Z600 so lost interest in the Z series at that time.
While browsing eBay I saw a Lenovo P720 for something like $500 and it piqued my interest. I still use dual optical drives and that is my primary requirement. My secondary requirement is at least three internal drive bays. I need at least PCIe gen 3 for networking; I'm not gaming anymore and only need an OK graphics card for video playback and occasional transcoding.
What's compelling about the P7x0 and P9x0 are each bay can accept two SATA/SAS drives--2.5" and 3.5"--using one carrier. I don't think the P520 has that capability. The backplane is typically attached to the motherboard's two mini-SAS HD (SFF-8613/SFF-8643) ports. But connecting the backplanes to the onboard mini-SAS HDs can only allow six drives to be used due to the Intel onboard controller. Using a PCIe controller will allow all eight ports to be used. Having one carrier mount two drives is a problem because configuring redundancy will require some planning. Many P920s do not come with a second backplane so I purchased another along with carriers. There are models meant for the P720/P920 for around $60 while there are ones for the P710/P910 for $20 with two carriers. The P720-/P920-specific backplanes do not come with carriers. I'm not sure of the difference so I purchased both.
The P920 permits mounting three 5.25" external drives. That is a plus because I can use the 3rd bay for whatever else I need. I have one of those 2x 2.5" drive chassis for 5.25" bays should I need to attach it. It's been sitting under my desk unused for 5 years. On the motherboard there are four additional SATA ports. Three are designated for the 5.25" bays (with only three power connectors) with one more for eSATA. The eSATA port can be reconfigured as a normal SATA (disable hot-plug) in the BIOS.
Talking about the BIOS, I am not a fan of graphical BIOSes so was pleasantly surprised to find I could change the interface to old school text. When I got the system the BIOS showed Intel AMT was enabled but no way to disable--those options were dimmed. The BIOS was dated 2020 and when I upgraded it to the latest released this year, AMT could be unconfigured. I typically PXE boot and run some Linux live distro on systems I acquire for testing. Lenovo's Linux BIOS updater doesn't work with the BIOS originally programmed so I had to install Windows.
I have WinPE set up and after I PXE booted it through the onboard i219LM (AMT-capable) ethernet controller (bottom one) it wouldn't see a connected cable. The other interface (i219) was able to see a cable and connect to my network to complete installation. Installing Windows was uneventful. The P920 allows one to distinctly control legacy/UEFI for each class of components to boot
(network, storage, USB, etc.). I still use legacy PXE. There is another setting in the BIOS to control overall legacy/UEFI boot preference.
Back at the hardware level, the P920 has five PCIe x16 slots, three PCIe x4 open-ended slots. Three x16 slots are tied to CPU2. It's unusual the reference and user guides don't have a block diagram, especially for an engineering workstation. Each CPU provides 48 PCIe lanes and three x16 use all available lanes. There are only four remaining lanes when counting the other slots. Perhaps the onboard SATA controller uses those four lanes and the USB and optical SATA, eSATA ports are tied to the C621 chipset. Lenovo has a program that monitors performance and I think it's similar to HP's Performance Advisor. HP's program shows a block diagram. I'll update this post if I find out anything.
Lenovo's Performance Tuner only allows application affinity. It shows a dashboard-like for system capacity but no diagram. I'll need to use Linux's lspci to see more details.
There is the ability to mount two M.2 drives but my barebones did not come with the carrier/heatsink so I had to get that, too.
I use the serial port on my Z620 in my lab and I found some USB-to-serial adapters don't work well with cygwin on my Z620 so I require the physical port. The P920's port does not have a standard header so I had to get that as well. The part description is not obvious but I found the part number on Lenovo's forums. The secret is using the part description "P920 com2".
Overall the system is quite heavy and maybe 4-6" longer than the Z600/Z620. The seller packed it very well with what appears to be original corner foam material.
Finally Lenovo touts a bunch of stuff you can connect to it such as Thunderbolt and the like. Thunderbolt requires an addon card that requires a passthrough cable between the card and the GPU. The motherboard has a dedicated header for the card. HP's Z8 Gen 4 has similar requirements. The motherboard has connectors for two more USB 3 connectors. Interestingly the motherboard has two fan headers for optical drives. I've never seen that before.
While I'm waiting for parts, I just installed two sticks of 32GB memory, two Xeon 6152s, Nvidia Quadro 2000, and a Samsung 850 Pro 1TB drive. The UPS and other powered-off systems used ~25W. After the system booted up to Windows it idles at ~110W which includes the 25W used by the UPS and other systems' PSUs/IPMI.
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