PCI Express 6.0 specifications have been made official

Written by Guillaume
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The first products using the new standard are not expected to appear for at least two years.

At the end of last year, we mentioned the first announcements of storage unit manufacturers targeting PCI Express 5.0. These products were presented at CES 2022 in Las Vegas a few days ago, but they are not expected to appear for a few more months, knowing that the platforms capable of using them can be counted on the fingers of one hand. At the moment, only Intel's Alder Lake architecture - launched last November - is capable of using PCI Express 5.0.

However, innovation continues and after several years of work, the PCI Special Interest Group (PCI-SIG) has just made official the specifications of the PCI Express 6.0 standard, which will logically take over the operations. According to AnandTech who relayed the information, the new standard is much more innovative than the two previous ones (PCIe 4.0 and PCIe 5.0). Although interesting in fact, these were only minor evolutions of a well-proven technology.

NRZ vs. PAM4 signaling

AnandTech explains that in order to achieve a further doubling of bandwidth, PCI Express 6.0 changes its signaling technique. Indeed, PCIe 4.0 and PCIe 5.0 remained on the previous technique of Non-Return-to-Zero (NRZ) signaling. This one only allows a signaling on two states, the classic high / low (or 0 / 1). In the case of PCIe 6.0, we move to Pusle-Amplitude Modulation 4 (PAM4) with a 4 that is not there by chance. It illustrates the signaling with four possible states: we move to a coding on two bits (00 / 01 / 10 / 11) and, in doing so, we double the amount of data transported while keeping the same frequency.

The PCIe 6.0 standard is thus capable of reaching a bandwidth of 256 GB/s on an x16 interface, whereas PCIe 5.0 had to "make do" with 128 GB/s on the same interface. A performance that already marked a doubling compared to PCIe 4.0 and it is more or less the leitmotiv of PCI-SIG: doubling the bandwidth with each new standard. Such a bandwidth will allow graphics cards and storage units to evolve significantly, but also and above all to make these two very greedy solutions cohabit without saturating the lines. However, the first compatible products should not arrive before at least two years.