The Upcoming PCIe 6.0 Specification is 4x Faster than PCIe 4.0

Bandwidth chart

PCI Express Gen 6.0 (PCIe 6.0) is in the works and slated for release in 2021. The upcoming specification brings even faster speeds for bandwidth-intensive workloads and devices. But do we need a new generation when we’ve hardly seen any PCIe 5.0 consumer devices in the market?

This article covers everything you need to know about the sixth generation of the PCI Express interface and whether or not you should upgrade.

PCI Express is a method used by CPUs to communicate with virtually every component in a PC, including graphics cards, storage drives, Universal Serial Bus (USB) ports, networking, and any other hardware hooked to the motherboard. It is also one reason why it’s easy to expand the functionality of a desktop than a laptop.

Since introducing the first PCIe specification in 2003, PCI-SIG (Peripheral Component Interconnect Special Interest Group), the organization responsible for defining the PCIe specification, releases a new generation after every three years. Each generation doubles the current PCIe bandwidth while maintaining backward compatibility with the previous generations.

Image Credit: PCI-SIG

Regarding the upcoming PCIe 6.0 specification, the Chairman and President of PCI-SIG, Al Yanes, affirms that “due to the continued commitment of our member companies, we are on pace to double the bandwidth yet again in a time frame that will meet industry demand for throughput.”

The PCIe 6.0 specification announcement comes in time as we start to see consumer devices based on the PCIe 4.0 specification. Yes, PCIe 4.0, not PCIe 5.0 devices. While PCIe 5.0 was finalized and released in 2019, there are no PCIe 5.0 in the market at the time of writing this article. The PCIe 6.0 specification might be available even before PCIe 5.0 has shipped.

For now, if you want to upgrade your hardware to the latest PCIe specification, PCIe 4.0 is your best shot. With multiple devices in the market that can take advantage of PCIe 4.0 bandwidth, including processors, motherboards, graphics cards, and storage drives, you can build your own PCIe 4.0 powered PC to enjoy faster gaming, faster content creation, and faster storage.

Enough of the chit chat. Let’s see what PCIe 6.0 has in store for us.

What is PCIe 6.0?

PCIe 6.0 is the sixth generation of the PCIe specification, expected to be released in 2021. Like other generations, PCIe 6.0 doubles the PCIe bandwidth to a whopping 256GBps (128GBps unidirectional) at 64GTps (Gigatransfers per second) raw bit rate, up from 32GTps of PCIe 5.0. That’s insanely fast.

To put it in perspective:

According to Tom’s Hardware, the specification is now “ready and functional,” but there two more stages until it is finally released in the market. Each new PCIe specification has to go through five checkpoints before it is released. The PCIe 6.0 specification is currently at the third checkpoint, version 07, released on November 2, 2020.

The next stage is version 0.9, where PCI-SIG members perform internal reviews for intellectual property. At this point, no more functional changes can be added to the draft. Therefore, early PCIe adopters such as AMD can begin working on their new PCIe 6.0 devices.

The last stage is version 1.0, the final release. PCI-SIG is working on the clock to have the specification finalized sometime later this year. Al Yanes is very confident that “2021 will be another thrilling year for PCIe technology with the full release of the PCIe 6.0 specification“. However, don’t get too excited, as it will take another couple of years until we see the specification in consumer devices.

How Does PCIe 6.0 Work?

PCI-SIG managed to hit double speeds by adopting PAM4 (Pulse Amplitude Modulation with 4 levels) signaling rather than Non-Return-to-Zero (NRZ), which was used in PCIe 5.0 and the other previous PCIe generations.

Image Credit: PCI-SIG

PAM4 has been around for a while, mainly used in ultra-high-end networking standards such as 200G Ethernet, InfiniBand, and GDDRX6 memory. However, while using a different signaling technology, PCIe 6.0 will still be able to interoperate with PCIe 5.0 and the other previous generations.

Previously, PCI-SIG doubled the PCIe bandwidth in new generations by increasing the transmission frequencies. However, doing this introduces some challenges, such as channel loss, because the signal becomes super unstable. Doubling the frequencies again in PCIe 6.0 could result in ever shorter trace length limits.

With PAM4, on the other hand, signals are now represented with four two-bit patterns 00/01/10/11, instead of the traditional 0/1 (high/low) signaling, which allows PCIe 6.0 to double the data rate of PCIe 5.0 without doubling the transmission frequencies. While PCIe 6.0 sends twice as much data as PCIe 5.0 per unit of time (Unit Interval), both have the same channel reach.

Image Credit: Intel

 

Since PCIe Gen 6.0 has two bits per Unit Interval (UI), it runs at half the frequency of PCIe 5.0, meaning channel loss won’t be severe on PCIe 6.0. In other words, it will be stable over long distances than PCIe 5.0.

However, cramming so much data on the same pipe increases the rate of errors, which prompts PCIe 6.0 to adopt a low-latency Forward Error Correction (FEC). The specification detects and corrects errors using Cyclic Redundancy Check (CRC) and Link Layer Retry.

If the receiver detects a particular packet is incorrect, it can ask for it again while maintaining low latency as possible. With CRC and Link Layer Retry, PCIe Gen 6.0 can run at high speeds while maintaining high data integrity.

How is PCIe 6.0 Better Than Last PCIe Generations?

While the significant benefit of PCIe 6.0 is increased bandwidth, you’ll better appreciate it when you understand how PCIe works. The bandwidth of PCI Express is determined by the lanes a CPU can allocate to devices and the speed at which those lanes operate.

PCIe Specification Bandwidth – X16 Configuration (Bi-directional) Gigatransfer Frequency
PCIe 1.0 8 GB/s 2.5 GT/s 2.5 GHz
PCIe 2.0 16 GB/s 5 GT/s 5 GHz
PCIe 3.0 32 GB/s 8 GT/s 8 GHz
PCIe 4.0 64 GB/s 16 GT/s 16 GHz
PCIe 5.0 128 GB/s 32 GT/s 32 GHz
PCIe 6.0 256 GB/s 64 GT/s 32 GHz

More bandwidth means more lanes. For instance, the new Nvidia GeForce RTX 3080 requires 16 lanes of PCIe Gen 4.0 to operate at full potential. However, with PCIe 6.0, you don’t have to use the full 16 lanes because you’ll get the same performance with just four lanes. This means the CPU has 12 extra PCIe lanes to allocate to other devices such as storage drives and add-in cards.

The same is true when you look at it in terms of storage. Most M.2 NVMe drives require four lanes of PCIe Gen 3.0 to operate at full speeds. With four lanes of PCIe Gen 6.0, you can connect eight of these drives and get maximum transfer rates on each of them.

Compared to the previous PCIe 5.0 specification, the upcoming PCIe 6.0 generation will have longer trace length limits, which alleviate channel loss. Not forgetting it runs at double the speeds, which means insanely faster storage speeds, gaming, and content creation.

Should you Upgrade to PCIe Gen 6.0?

Frankly, PCIe 6.0 is overkill for the average consumer. Most of today’s graphics cards (hungriest PCIe devices) can’t even saturate a PCIe 3.0 interface. Is there a point in having a new standard?

It turns out yes, but not what you are expecting—PCIe 6.0 isn’t really targeting consumers. PCIe 3.0 and 4.0 is good enough for gaming, content creation, and everyday desktop use. The ultra-high-speed interface can better be leveraged by commercial environments, especially data-sensitive markets such as data centers, machine learning, AI, cloud, storage, and networking.

For instance, in a server or data center, it is not always about speeds but also the number of drives you can connect without compromising performance. A single PCIe 6.0 X16 slot can support a whopping 32 M.2 PCIe 3.0 drives. However, on a PCIe 3.0 board, you can only connect four if you want them to run at full speeds.

The upcoming PCIe 6.0 specification is an excellent solution to data-driven and bandwidth-sensitive markets, helping them leverage the ever-growing amount of data every day to drive innovations. That means smarter self-driving cars, scalable cloud architectures, faster storage speeds, increased data integrity, and more.

PCIe Gen 6.0: When Could we Expect?

We expect PCI Gen 6.0 to be finalized in 2021, according to PCI-SIG, but it will take another year or more to arrive in consumer devices. In the news, Intel confirmed their upcoming 12th gen Alder Lake processors will debut in 2021 with PCIe 5.0 support. AMD’s Zen 4 processors are also expected to hit the market with PCIe 5.0 sometime in 2022.

Therefore while PCIe 6.0 will, without a doubt, arrive this year, but the earliest we will receive PCIe 6.0-enabled devices is 2022 or later.

Conclusion

PCIe 6.0 is coming this year with double the speeds of PCIe 5.0. The specification uses PAM4 signaling to double the data rates while keeping the same channel reach as PCIe 5.0. Other great benefits of the upcoming specification are increased data integrity and reduced channel loss.

PCIe will significantly benefit the data-sensitive industries such as data centers and machine learning, improving available bandwidth and the number of devices connected. At this point, PCIe 3.0 and 4.0 are more than enough for consumers, but you can still upgrade your setup in the future to enjoy the benefits of PCIe 6.0.

What PCIe generation are you using, and do you think the industry is ready for PCIe 6.0? Let us know in the comments section below.

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