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5 ways to make use of PCIe Bifurcation in your PC
Beyond GPUs, a lot of PC builders don't think much of the humble PCIe slot, and that's a shame, because they enable so much functionality. Even if you're not a power user, it's not difficult to see how quickly you can run out of PCIe slots, especially once you factor in M.2 expansion.
This is where PCIe bifurcation comes into play. Bifurcation of PCIe allows you to split what would be a 16x slot into two 8x slots, or even four 4x slots. With how high bandwidth has climbed for PCIe, there are so many possibilities that bifurcation enables, and here are 5 of my favorites.
SFF PCs benefit massively
When slots are at a premium, bifurcation helps
When you're building a system in a heavily enclosed space, you're trying to squeeze every bit of functionality that you can into a very small physical space. PCIe bifurcation is one of those things that you can harness to get the most out of a single PCIe slot, which is usually all you have to work with on an ITX motherboard.
With PCIe 4.0 and 5.0, the difference in bandwidth between 16x and 8x isn't enough to make a noticeable difference in gaming or workstation use in the vast majority of situations. If you're crafty about fitting it into the physical space, it's possible to have expansion cards, storage, and a GPU running off of one slot. It's not easy, but it can be done.
Expanding NVMe support in larger systems
All of the NVMe drives!
Most consumer motherboards only offer 2 to 3 M.2 slots, but with PCIe bifurcation using an adapter card, you can load up to 4 drives and run them off of a single PCIe 16x slot. Even when split in two, three, even four ways, PCIe 4.0 and above grants more than enough bandwidth to saturate most SSDs. Setups like these have the ability to potentially outperform enterprise storage arrays, especially when it comes to price-to-performance.
HBAs and RAID
Even more storage
Host bus adapters and RAID cards require a certain amount of PCIe bandwidth in order to connect all the storage in an array together. PCIe bifurcation can allow you to combine multiple HBAs on one slot for large-scale storage arrays.
Instead of buying a whole new (potentially very expensive) server motherboard with more dedicated PCIe slots, bifurcation gives you the flexibility to run advanced ZFS and RAID configurations without the added cost. Unless you're sure your workload requires it, using fast NVMe storage, or you intend on pushing it, there's virtually no way the slot's bandwidth will be exceeded.
Accelerators
Especially for local LLMs
Instead of investing in one large, expensive GPU, you can harness multiple smaller cards in a single slot using PCIe bifurcation. Unlike the dead and buried technologies of SLI and CrossFire for gaming, AI and other workstation workloads can harness multiple cards incredibly well. AI especially scales better across multiple cards instead of relying on one massive GPU core. For running local LLMs, bifurcation really is indispensable, but it doesn't stop there.
For video editing, you can use a secondary GPU as an accelerator for things like timeline scrubbing and in-application performance, while the other can be used for background rendering. You can also combine the power of both for rendering in parallel, but your mileage may vary.
Thunderbolt expansion
A welcome addition for any setup
If you have devices that support it, Thunderbolt add-in cards can be a game-changing addition to your setup. The sheer bandwidth they can provide can't be matched, and add in support for things like daisy-chaining displays or high-speed access to high-capacity, multi-bay storage arrays means you don't have to compromise on performance in favor of cleanliness in your setup.
Most consumer boards won't support more than one Thunderbolt AIC, but with bifurcation, you can get away with adding multiple if needed. If you're looking into consolidating external storage, displays, and networking onto only a few cables, this is one of the better solutions, and it's possible on consumer hardware with PCIe bifurcation.
PCIe bifurcation is awesome
While it's not something that's possible on every system and your plug and play mileage will vary, if you manage to get everything working, the benefits are hard to ignore. One PCIe slot can be the backbone of your system, and multiple PCIe slots can mean incredible expansion opportunities. It's a great way to get the most out of the hardware you already own, without the need to upgrade to boards with more slots.