Your PC probably has a slot that looks like this.
It's a PCI Express X16 slot, and it's commonly used for graphics cards,
as it's one of the fastest connections on your motherboard. Even the chonkiest, most powerful GPUs can be handled
by a single one of these slots, no problem. But there is another.
Did you know that PCI Express X32
is a real thing that actually exists? What the heck would you do with a slot that's twice as long?
Well, to be clear, it's very difficult to find slots physically bigger
than that standard X16 size. Remember that those numbers,
when we're talking about PCI Express, refer to the number of lanes,
not necessarily the physical size of the slot. A tiny M.2 SSD often uses four PCI Express lanes,
even though the connector is quite a bit smaller than a regular PCIe X4 sized slot.
How exactly does PCI Express X32 work then?
But it turns out that the PCI Express standard doesn't support a single link greater than X16.
The reason for this is because it's very difficult to actually implement links this wide in hardware.
You see, when you send data down a PCI Express link,
say to a graphics card, that data is striped across multiple lanes,
and doing this is not trivial. When the data arrives wherever it's going,
it has to be deskewed, meaning synchronized.
Although PCI Express is a serial interface that doesn't require the data on each lane
to arrive at exactly the same time, synchronizing the data still involves hardware overhead.
And once you start getting past 16 lanes, it's just too much to keep up with.
So instead of having one big slot, these higher PCI Express connections
use a trick called driver binding. Essentially, this allows multiple PCIe devices
to talk to each other and coordinate their traffic
so they can act as one big device. So a PCIe X32 link is actually two X16 links
mashed together in software, with the devices installed in two normal X16 slots.
The performance overhead involved with driver binding for X32 isn't too bad.
But if you were to theoretically go up to say X64,
you'd likely need more hardware, as at that point you just have too many transactions
for your poor system to handle. But wait a sec, why the heck would you need
that much bandwidth to begin with? Now the appeal of having this many PCI Express lanes
isn't so you can do something like squeeze more performance
out of your graphics card. Even an RTX 4090 barely improves going from eight lanes
to 16 lanes on a PCIe 4.0 slot.
Instead, driver binding is used in applications where all the bandwidth you can get is appealing.
You often see X32 links in certain kinds of networking cards,
mostly for server and data center use. Although NVIDIA is obviously known more for GPUs and AI,
they make a line of network adapters that supports both Ethernet
and another high speed networking protocol called Infiniband.
This product, for example, goes into a standard PCIe Express X16 slot,
but it comes with a second auxiliary card with the same connector.
They work in tandem to provide an X32 connection for extra bandwidth in case you're using
a previous revision of PCIe Express that doesn't provide enough bandwidth
to take full advantage of the network adapter's speed. There's also a special cable connecting them
to allow them to share data while taking some of the pressure off of the PCIe Express bus itself.
And connecting multiple machines with crazy amounts of bandwidth isn't even a rare use case.
With how much growth we've seen with data hungry cloud services
for applications like AI, gaming, and ultra high def video,
data centers are already moving towards 400 gigabit connections or even beyond.
That's 400 times faster than what you'll find
in most garden variety desktop PCs, which is also part of why you simply don't need
PCIe Express X32 in your personal rig.
Although I'm sure some of you are already thinking of ways you're gonna justify your purchase.
Hey, thanks for watching this video. Like it if you liked it. Dislike it if you disliked it.
Check out our other video on PCIe Express 6.0.
Comment below with video suggestions and don't forget to subscribe and follow to TechWiki,
the channel that's all about doing the tech real quick.