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May 3rd, 2025 01:26
T5820 PCIe Questions
Hi all,
A few quick questions about the 5820 workstation. Mine has a Intel Xeon W series chip.
Is there any official documentation of the PCIe bifurcation available? People here and there talk about being able to split slot 2 into four x4 lanes for NVMe drives but is there any official docs on this? What about the other PCIe slots, i.e. does slot 1 support bifurcation? How about the lanes used for the flexbay NVMe drives?
Has anyone had any experience using the PCIe lanes exposed out of the SFF 8643 connectors? The fact they can be used with NVMe drives makes me thing they are just standard PCIe x4 outputs as described in the SFF 9402 reference guide (or maybe the SFF 8613 connector and SFF 9401, I'm not entirely clear on the difference between the two as they seem to be identical). However, the OEM flex-bay adapters appear to have a FPGA on board and a relatively complicated interface board which makes me think there may be something else going on in there. Again, does anyone have resources to explain this? The workstation manual is very light on specific information.
Any help would be appreciated.
Chino de Oro
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May 3rd, 2025 15:58
Re: Is there any official documentation of the PCIe bifurcation available?
Unfortunately, there is no official documentation of PCIe bifurcation available for Precision 5820 besides the marketing datasheet and owner manual.
However, those general information were/are sufficient enough for me to understand and properly setup the storages in Precision 5820. Here is information I know about the system bifurcation.
This system natively support bifurcation on slot 1 (PCIe x8), slot 2 and slot 4 (PCIe x16). There are two miniSAS ports on motherboard, which are PCIe x4, hence, are not applicable with bifurcation.
Dell Ultra-Speed Quad and Ultra-Speed Duo adapters were tested and validated to support multi-NVMe be installed on each PCIe slots. Some aftermarket adapters also work, such as Asus Hyper. There is specific backplane requires that will support NVMe drives in flexbay connecting to miniSAS ports.
DellName1234
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May 5th, 2025 02:38
@Chino de Oro Thanks, that's good to know that at least slot one should support x4 x4 mode.
Pity there isn't more information and flexibility available for these boards as they have plenty of lanes just no easy way to make use of them all.
Fingers crossed the pinout of the Mini SAS HD ports isn't something exotic and will let me put my own adaptors in.