Can I use Broadcom HBAs as a PCIe Switch?

[pwn02]

It may not make sense at all. If you have suggestions please let me know.

Ex. Can I plug in something like an SFF-8654 to PCIe card to each of the ports on the 9500-8i and use it with other PCIe devices ex. Wifi cards or something? I'm thinking of designing a custom card for it. So maybe something like

Rationale: The 9500-8i cards are like $100 and we have some left over. They are cheaper than ASM2824 based cards and adapters allow easier and more flexible mounting of the downstream cards.

(2x Wifi Card on adapter <-x4 SFF-8654 cable -┐ )
( ┣-x8 SFF-8654 cable-> ) x2 <--> Broadcom 9500-8i <-PCIE x4-> Motherboard
(2x Wifi Card on adapter <-x4 SFF-8654 cable -┘ )

ex. Adapter #1 DIPCIE2XD01 | PCIe 4.0 Expansion | PCIe Gen 4 SFF-8654 x4 to two PCIe x4 (x2 mode) slots Expansion | DIPCIE2XD01


or

Wifi Card/Serial IO card on adapter <-SFF-8654 cable <-┐
┣>Broadcom 9500-8i <-PCIE x4-> an Industrial ITX MB
Wifi Card/Serial IO card on adapter <-SFF-8654 cable <-┘

ex. Adapter #2 SFF-8654 8i to PCIe 4.0 x16 External Graphics Card Adapter - AliExpress 502

 

[zir_blazer]

I recall having made a similar question when Tri Mode adapters began to appear a few years ago, as I was curious on this very same capability. These cards NEED to support PCIe on the ports to interface with a standard NVMe drive so they can be considered glorified PCIe Switches. I would assume that getting it working as a dumb PCIe Switch would be equivalent to IR (RAID) vs IT (HBA/Passthrough) mode, so the question is whenever these cards actually provide a way to do that so that they would be equivalent to having a PCIe Switch on a card, similar to this.

The adapter you linked may not necessarily work, at least not with both slots, since it assumes that you can bifurcate a 4 lane port to 2x/2x. Keep it simple with standard PCIe 4x slot.

 

[NablaSquaredG]

Ex. Can I plug in something like an SFF-8654 to PCIe card to each of the ports on the 9500-8i and use it with other PCIe devices ex. Wifi cards or something?

Nope.

The Broadcom Tri-Mode adapters are so bad, they don't even pass NVMe devices to the OS as PCIe devices. Instead they will appear as "normal" drives, not NVMe, with the card and driver translating...

 

[CyklonDX]

It does work if the adapter you are using has support for pcie switch direct attach option *(It should be in uefi option - on your controller)
The 9500 will then behave as pcie switch, and show all pcie devices directly.
*Not all have support direct attach mode, i think only ones with broadcom PEX88000, but pcie switch mode may be just related to J7 to enable support for advanced features - i didn't go that far. (but for now it appears same named 9500's may be not equal)

 

[NablaSquaredG]

The 9500 will then behave as pcie switch, and show all pcie devices directly.

, i think only ones with broadcom PEX88000

you are comparing 9500 which is a HBA with a PCIe switch?
Totally different things

 

[CyklonDX]

you are comparing 9500 which is a HBA with a PCIe switch?
Totally different things

Some 9500's come with that pcie switch chip, but itself
The DCSG-SAS 3416/3516 chips have listed support of up to 4 direct attached pcie devices in direct attach mode.

The 9500's can work in 4 different modes
x4 NVMe Drives
x2 NVMe Drives
x1 NVMe Drives
x4 Switch mode

In each mode it supports different amount of nvme's in different lane density, and in switch mode up to 4 pcie devices at x4 pcie.