Although we still haven't gotten PCI express 5.0 devices
in our hot little hands yet, believe it or not, the PCIe 6.0 specification
has already been released. And as you may have guessed, it's insanely fast.
At 126 gigabytes per second one way on an X16 link,
it's twice as fast as 5.0, four times as fast as 4.0,
which is fairly new on the market, and eight times faster than the 3.0 devices
many of us idiots are currently using.
But how do they make it so fast? And more importantly, does it have real relevance for you, the home user,
or is it just overkill? To find out, we spoke with Dibendra Dash Sharma,
an Intel fellow in their data platforms group, and we'd like to thank him for lending his time
and expertise. So unsurprisingly, PCI express 6.0 is backwards compatible
with all the previous generations of PCIe, but if you go all the way back to version 1.0,
you could only get up to four gigabytes per second one way from an X16 slot.
Now, we're pushing 32 times as much data
through the same link. Older revisions of PCIe express got faster and faster
because they increased their transmission frequencies, but it turns out you can only do this so much
before the signal becomes super unstable. It's kind of similar to how a 5 gigahertz Wi-Fi connection
is faster than a 2.4 gig link, but it's also not as stable at long distances.
So instead, PCIe 6 uses a technique called PAM4,
which can actually carry two bits of data at the same time instead of just one.
Unlike traditional signaling, where one voltage represented a zero
and a second voltage represented a one, PAM4 uses four different voltages,
and each one corresponds to either 00, 01, 10, or 11,
meaning twice as much data is sent per unit of time.
However, shoving more stuff through the pipes is, just like in regular life, not the greatest idea.
In this case, it increases the rate of errors, and even with the PCIe special interest group
adding a few nanoseconds of latency to reduce the error rate to about one bit per million,
that's still a lot of potential errors when you consider how much data flows
through a typical PCIe express link. However, a few bytes in each chunk of data that's sent
are reserved for error checking and correction. If the receiving device sees that a packet is incorrect,
it can ask for it again using just a few bytes of data.
Because this error correcting scheme is quite lightweight, it only adds a very small amount of latency.
So this way, PCIe 6.0 can operate at very high speeds
without constantly losing signal integrity. In fact, it's estimated that instead of an error rate
of one bit in a million, PCIe 6.0 can operate
with only one unfixed error every billion, billion hours.
So you'll probably never have to worry about it unless you're an elf from Middle Earth.
But Riley, hold on a minute. All this performance is fine and good,
but my graphics card doesn't even saturate the PCIe express slot in my computer today.
Why should I care about this? Well, one reason is that as we continue to ask
for more and more out of our devices, having the fattest pike possible,
will ensure that we can do things like hit our SSDs with mega-sized downloads, stream 4K and 8K HDR video,
and keep up with the ever-increasing demands video games put on our graphics cards all at the same time.
But going beyond just your home PC, think of all the cloud services you utilize
on a daily basis for applications from voice assistance
to IoT devices to self-driving cars. Well, assuming you can afford one.
All these gadgets need a high bandwidth interface that can process data with minimal latency.
Think of an autonomous car that quickly has to get data from a camera to a CPU to a 5G modem,
which then goes into a server somewhere that has to respond quickly to aid and hazard recognition
and is also moving data around internally for machine learning.
That's a lot of data. On both ends of that connection,
PCI-Express 6.0 could deliver enough speed to make the experience seamless
and maybe even tell you about an icy road ahead before you end up in the ditch.
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