What is Oculink? It sounds like the tech that Dr. Octopus uses
to control his robot arms, legs, but it's actually an open standard PCI Express connector
with a compact form factor created to compete with Thunderbolt and USB.
Despite being around for nearly a decade, Oculink has remained a relatively obscure standard,
which is a shame because it's actually pretty awesome.
Oculink stands for optical copper link and was initially envisioned as a combination
of copper and optical fiber. However, the need to convert electrical signals
into light signals and back again means that fiber optics are relatively inefficient
over short distances. So the whole optical element was eventually scrapped,
though the name remains. CU stands for copper's chemical symbol,
which is itself based on copper's Latin name. Otherwise, it would be spelled acolink,
and I think we can all agree that's just terrible. Aco, acolink?
Oculink was developed by PCI SIG,
the body charged with creating standards for the PCI interface.
Oculink 2.0, the most recent version, launched in 2017 with a new connector,
similar to the standard DisplayPort connector. It boasts support for up to four PCIe 4.0 lanes
and up to eight gigabits per second per lane for a total of 64 gigabits per second of bandwidth,
though notably an eight lane version also exists.
That places the four lane version above both Thunderbolt 3 and 4
in terms of transmission speed and on par with Intel's upcoming Thunderbolt 5,
which is supposed to launch sometime in 2024 with 80 gigabits per second of bi-directional bandwidth,
but only 64 gigabits per second of PCIe bandwidth.
Now beyond bandwidth, a primary advantage of Oculink is that it's far more cost effective.
That was particularly the case prior to 2018
when Thunderbolt became a royalty-free standard, but it's still true, albeit to a lesser degree,
simply because it uses cheaper components and doesn't require quite the same amount
of precision to manufacture. It's that combination of high performance
and a lower price point, which has garnered Oculink a devoted following,
especially on the server side. Now that doesn't mean there's no consumer side applications.
Oculink reduces the performance gap between internal and external GPUs to a very low margin
because it's significantly faster than Thunderbolt 3 or 4. What Oculink doesn't do, that Thunderbolt does,
is provide solid support for hot plugging. With Oculink, you're typically going to want
to shut down the system before swapping components, or it might crash.
Oculink only uses PCIe signals, making it great for connecting a graphics card,
network card, or storage controller, but Thunderbolt is basically a two-in-one DisplayPort
slash PCIe connector, which can provide video
in addition to power and data transfer. Oculink only transfers data,
so an Oculink setup is always going to need at least two cables if you want to connect
and power a device at the same time. Not to mention that Thunderbolt ports are compatible
with USB-C cables. These factors, plus having daddy Intel as a backer,
mean that Thunderbolt has much broader adoption in the consumer electronic space.
And that ubiquity gives Thunderbolt a definite advantage
in terms of convenience, especially for less tech-savvy users.
Now, you could, hypothetically, create a version of Oculink with some or all
of the bells and whistles that Thunderbolt offers, but that might be missing out
on what makes Oculink truly great.
Thunderbolt is designed to be a generalist connector, a jack of all jacks, if you will.
It's made to do several different things quite well, wrapped up in a convenient user-friendly package,
but generalization comes at the expense of specialization,
and lower data transfer speeds and throttling are a result of that compromise.
A similarly flexible and multi-purpose Oculink connector
would also probably be far more expensive, because when you're combining a bunch of complex components
exchanging a bunch of different signals in a very, very small space,
that demands both creative engineering and extremely precise manufacturing.
Otherwise, there's gonna be interference between these different signals, and it won't be reliable.
Thunderbolt 5 is supposed to give us the best of both worlds,
the convenience and versatility of earlier versions of Thunderbolt,
but with far faster data transfer speeds.
It'll be a while before we can see real-world benchmarks, but I mean, that sounds awesome.
It bears remembering, however, that so long as these connectors remain a bottleneck,
and performance loss is non-trivial, there will always be space for an improved version
of the Oculink or another specialized connector to come along and do it better.
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