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The PCI-SIG finalized the PCIe 4.0 specification with doubling the data to 16GT/s from 8GT/s in PCIe 3.0 in 2017. Products implementing this technology have begun to hit the market in 2019. Earlier this year, AMD announced it X570 chipset would support the PCIe 4.0 interface and Phison also introduced the world’s first PCIe 4.0 SSD. With the increasing companies are working on PCIe 4.0 related product development, Cadence, as the key and leading PCIe IP solution vendor in the market, has strived for continuous enhancement of its PCIe 4.0 to be the best in the class IP solution. From our initial PCIe 4.0 solution in 4 years ago (revealed in 2015), we have made many advancements and improvements adding features such as Multi-link with any lane assignment, U.2/U.3 connector, and Automotive support. The variety of applications that PCIe4 finds a home in require extensive robustness and reliability testing over and above the compliance tests mandated by the standard body, i.e., PCI-SIG.
PCIe 4.0 TX Eye-Diagram, Loop-back Test (Long-reach) and RX JTOL Margin Test
Cadence IP team has also implemented additional "stress tests" in conjunction to its already comprehensive IP characterization plan, covering electrical, functional, ESD, Latch-up, HTOL, and yield sorting. Take the Receiver Jitter Tolerance Test (JTOL) for instance. JTOL is a key index to test the quality of the receiver of a system. This test use data generator/analyzer to send data to a SerDes receiver which is then looped back through the transmitter back to the instrument. The data received is compared to the data generated and the errors are counted. The data generator introduce jitter into the transmit data pattern to see how well the receiver functions under non-ideal conditions. While PCI-SIG compliance can be obtained on a single lane implementation, real world scenarios require wider implementations under atypical operating conditions. Cadence’s PCIe 4.0 IP was tested against to additional stressed conditions, such as different combination of multi-lanes operations, “temperature drift” conditions, e.g., bring up the chip at room temperature and check the JTOL at high temperature.
PCIe 4.0 Sub-system Stress Test Setup
Besides complying with electrical parameters and protocol requirements, real world systems have idiosyncrasies of their own. Cadence IP team also built a versatile “System test” setup in house to perform a system level stress test of its PCIe 4.0 sub-system. The Cadence PCIe 4.0 sub-system is connected to a large number of server and desktop motherboards. This set up is tested with 1000s of cycles of repeated stress under varying operating conditions. Stress tests include speed change from 2.5G all the way to 16G and down, link enable/disable, cold boot, warm boot, entering and exiting low power states, and BER test sweeping presets across different channels. Performing this level of stress test verifies that our IP will operate to spec robustly and reliably when presented with the occasional corner cases in the real world.
For the demonstration of Cadence PCIe4 PHY Receiver Test and Sub-system Stress Test, see the video:
For more information on Cadence's PCIe IP offerings, see our PCI Express page.
For more information on PCIe in general, and on the various PCI standards, see the PCI-SIG website.