Hi.
My name is Rick Eads.
I am the product portfolio manager for PCI Express tools for Keysight Technologies.
I also have responsibility for the transmitter test tools for our oscilloscope line.
And I also serve on the PCI-SIG board of directors and am secretary to the PCI-SIG, working in
the electrical workgroup, the card electromechanical workgroup, and the serial enabling workgroup.
Now, within the PCI-SIG, our efforts right now are focusing on PCI Express Gen4, and
we look forward to operating PCI Express at 16 Gb per second in the near future.
One of the key challenges of measurements for NVMe, or nonvolatile memory – express,
is in the physical layer validation.
And so, what we have here with our high-end oscilloscope, that operates at 33 GHz, is
we're able to measure the signal quality of the transmitter.
NVMe operates at speeds up to 8 Gb per second.
That means the unit interval timing is as short as 125 ps.
So, being that fast, PCI Express, the underlying technology for NVMe, is subject to impedance
discontinuities in transmission lines.
It's subject to signal quality concerns related to the packaging and the actual layout of
the ICs themselves.
So, one of the things we want to do is to ensure that the signal quality coming from
the transmitter is within the parameters specified in the PCI Express 3.0 specification.
One of the implementations of NVMe is with – an SSD drive, as shown here, using a connector
called SFF8639, or small form factor 8639.
This is a four-lane PCI Express interface.
Now, this is different than the standard PCI Express interface that you would see on a
server.
So, somehow we need to get access to these signals in order to test signal quality.
One approach to that is to use this particular adaptor card that converts SFF8639 to the
standard CEM form factor for PCI Express, and this allows us to use the standard PCI-SIG
sourced compliance baseboard 3.0.
So, by placing this in the serial cable's brand adaptor, we're able to then plug the
adapter into a CEM slot in the PCI-SIG connector.
And then we're able to use PCI-SIG's own tools or own fixturing in order to break out the
NVMe – signals and measure them on the oscilloscope.
Another option that we have for breaking out the SFF8639 fixtures is – or signals- is
using this fixture from a company called Wilder Technologies.
And as you can see, we have an SFF8639 connector that's native, and we can take our SSD drive
and plug it in directly.
Now, this is a little bit different from the standard PCI-SIG fixture plus adapter.
What's nice about it is it has better signal quality.
Overall, we'll measure about 30 percent to 40 percent better eyes at 8 Gb per second.
However, we need to provide power, we need to provide an external clock, and we also
need to provide a mechanism externally to toggle the device through the different PCI
Express compliance states.
Once you have your NVMe device that has been properly fixtured and then configured to drive
the – PCI Express transmitter compliance pattern, the next step is to test the transmitter
signal quality.
And for this, we have shown here the N5393D PCI Express transmitter compliance package
that runs on our DSA X-series 90000 series oscilloscopes from Keysight Technologies.
And so, we'll use this application to select the speed at which – of the signal that
we're going to test.
We will then select the types of tests that will run, whether they're endpoint or root
complex tests, and then the software will actually go through and perform all of the
necessary compliance tests in an automated fashion, resulting in an HTML formatted output
that has screenshots, has max and min values, and has margin information that tells us just
how much we passed or failed by when the results are presented.
Once again, this is Rick Eads, and I'd like to thank you for your time as we’ve – talked
about PCI Express and NVMe technologies.
For more information, please go to keysight.com.
And have a great day.