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To meet the ever-growing need for data computation, enterprise and data center systems are upgrading to PCIe Gen 4. In this video, we will focus on the PCIe Gen 4 driver and demonstrate how it can help to extend links between host and endpoint.

In PCIe Gen 4, the data rate has doubled to 16 gigabits per second. But the maximum channel loss spec increases by only 27%, from 22 dB in Gen 3 to 28 dB in Gen 4. This means most server topologies today will not meet the 28 dB insertion loss spec of Gen 4.

One way to resolve this issue is by using exotic materials and connectors. However, these board materials can substantially increase platform costs, and in certain cases, are still not able to resolve the signal integrity challenges. A second approach is to use signal conditioning solutions such as a redriver or retimer to help extend the reach between host and endpoint beyond the 28 dB spec limit.

In this video, we will be discussing the redriver solution. Redrivers are protocol-agnostic devices that provide signal conditioning to the incoming analog signal. It compensates for channel loss, a loss that increases with frequency, with an inversely linear gain called a CTLE. The signal may then go through a linear driver stage.

If the redriver's receiver detect block detects a termination, then the signal will then pass on to the CPU or endpoint. Let's look at how this type of device is used to extend reach in a server platform.

Here we have a PCIe Gen 4 server platform demonstrating a rack server storage solution. The PCIe signal is generated from the CPU, travels through the motherboard trace, and then goes through a number of connectors and cables before it is received by the SSD.

The total loss of this system is far beyond a 28 dB limit, and as a result, the eye of the PCIe Gen 4 signal is closed and the connected SSDs will not be able to establish a Gen 4 link. Its ability to quickly read and write information to the SSD will be limited. As seen on the monitor, they are unable to establish a Gen 4 link due to poor signal integrity.

After we add the redriver, the net loss of the channel will be within the 28 dB spec, enabling a Gen 4 connection. Our redriver provided a boost to the signal, compensating for the channel loss. As a result, the throughput of the SSDs increased, and they are able to establish a Gen 4 link, as we can see on the monitor.

Now let's take a look at another topology. Here, we have a network interface card, also called a NIC, plugged into one of the CEM slots far away from the CPU. Again, we see a failure to establish a Gen 4 link. Under normal conditions, a Gen 4 link with this high amount of loss would not be able to reliably connect to the NIC.

However, with the redriver, we are able to establish a Gen 4 link. This extension was possible with the DS160PR410 PCIe Gen 4 redriver, the latest addition to our PCIe signal conditioning solution family. The DS160PR410 provides 18 dB of boost at 8 gigahertz, which enables stringent server topologies, as demoed previously.

This analog redriver has a low latency of 100 picoseconds and consumes only 130 milliwatts per channel of power, which means no additional heat sink is required. Also, a reference clock is not needed, reducing the overall cost of your BOM and simplifying your signal conditioning solution.

This device has passed all the PCI-SIG testing and has been added to the PCI-SIG Integrators List. If you would like to learn more about this redriver, or our PCIe signal conditioning portfolio, please visit the link below.

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