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Aurora R9, PCIe bifurcation support?
I just bought the new Alienware aurora r9 and I wanted to add multiple m.2 drives to it. So I purchased an ASUS HYPER x16 PCIe extension card with 4 NVMe slots on it. After installation I could only find 1 drive discovered on Windows and after some research I realized I need a motherboard with PCIe Bifurcation to make the system recognize all the m.2 drives on the ASUS card, but I couldn't find any option in BIOS settings. Any ideas? I have a feeling the answer is that Alienware doesn't support this.... so is there any other way to get multiple m.2 drives on my rig?
GTS81
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October 22nd, 2019 12:00
I think that's why @Techgee mentioned the need for that expensive card because the PCIe traffic controller chip on it essentially takes over the BIOS' job and all BIOS needs to do is to communicate with that chip.
I'd add on top of @r72019's comment on the neutered x8 PCIe slot.
This Is Not An All-powerful Enthusiast-customizable PC
The more you try to get power-user feature enabled on your R9, the more frustrated you will become. In the end, you either end up:
Enjoy!
Techgee
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October 22nd, 2019 07:00
Just use an add-in card with Bifurcation support on the card. I posted a list of quad M.2 NVMe PCIe add-in cards with Bifurcation support elsewhere on Dell's Forums here.
r72019
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October 22nd, 2019 08:00
You should also note that the R9's GPU slots on the z370 board are neutered to x8. Even if BIOS did allow for bifurcating the PCIe lanes, you'd be at x4 x4. Also, quad nvme cards are wired for x4x4x4x4, and because the R9 has only x8, you'll be limited to 2 NVME PCIE drives on one card with that setup (as the last 8 lanes would be routed to the dead lanes on the motherboard).
Techgee
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October 22nd, 2019 09:00
I have a quad M.2 NVMe card with bifurcation (its actually a PCIe switch chip) with only x8 PCIe lanes on the motherboard side. System sees all 4 SSDs.
While bifurcation on a motherboard does a one-to-one assignment of PCIe lanes to specific devices and requires x16 lanes for (4) x4 devices, bifurcation on a card has no such requirement. Instead, the motherboard sees all the lanes in its PCIe slot as usable by all devices on the card in the slot. It can and does put data on any of the motherboard lanes to go to any of the devices. Otherwise, when sending data to the card the motherboard would have to know about which lanes are assigned to which devices on the card - which is the definition of bifurcation on a motherboard!
Data traffic to/from devices on a card with bifurcation is "load balanced" among all the lanes on the motherboard - regardless of number of lanes on the motherboard. Yes, this means in theory a quad M.2 NVMe card with bifurcation will run and have all 4 M.2 devices visible in a x8, x4 or even x1 slot (disregarding power requirements and possible need for a riser, plus decrease in overall performance, of course)!
james00bond00
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October 22nd, 2019 12:00
Those are really expensive though. My asus card was only $60. That said, wouldn't i still need bifurcation available on my bios?
Techgee
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October 22nd, 2019 13:00
I justified the cost of the card by comparing it to the cost of 4 1TB to 2TB Samsungs.
No, you don't. I'm actually running one in a circa 2009 X58 chipset Dell, which obvious doesn't have bifurcation.
That's pretty much it. You could think of a quad M.2 card with a PCIe lane switch chip as a combo card (analogous to something like a USB / SATA combo card), with the PCIe switch chip managing the traffic between the 4 M.2 devices and the motherboard.