Even with the best microSD cards for Raspberry Pi, you get maximum sequential transfer rates around 40 MBps and 4K random reads and writes, the kind that matter most, are under 5 MBps. To get faster storage, you can boot your Raspberry Pi from a USB SSD, but many Pi fans would like to go a step further and attach a storage device directly to the PCIe bus and some have even tried soldering on special chips to make this happen. These hacks may not be necessary in the near future, because the Raspberry Pi Foundation is looking at ways to add PCIe NVMe storage support to a future Pi, most likely the upcoming Raspberry Pi Compute Module 4.
On yesterday’s episode of the Pi Cast, Raspberry Pi Trading CEO Eben Upton said that he and his team are planning to launch the Compute Module 4 within the next year and hope to support NVMe storage on it.
“The Raspberry Pi Compute Module, CM4, we will support NVMe to some degree on that, because of course it [Raspberry Pi 4] has a PCI Express channel,” he said. “We have a single lane Gen 2 which is used to supply USB 3 on the Raspberry Pi . On the [Compute] Module that would be exposed to the edge connector and we’re likely to support NVMe over that.”
Raspberry Pi’s Compute Modules are designed for embedded and industrial applications and therefore don’t come with any I/O ports. Developers build their own boards and attach the Compute Modules to them. Most end users probably wouldn’t buy a Compute Module, which leaves us wondering about NVMe support on a traditional model B and according to Upton such support is possible, but it would require a lot of changes.
“In the core product, maybe a future Raspberry Pi may pick up something, but it is challenging,” Upton explained. “It is not without cost, both in terms of the silicon and in terms of the connector, as the connectors are not free. Also providing board area for the connectors, if you look at the Raspberry Pi there's not obviously not room for an M.2 slot”
When asked about a possible Raspberry Pi 4 Model A, Upton hinted that it’s possible a future Model A could have NVMe support.
“What would a 4A look like? We have a decision to make about what we do with the USB 2. The USB 2 on Pi 4 is brought to the power jack, the OTG is brought to the power jack so we’d have a question in our minds about whether we undid that, probably, as we do on other A boards [and] brought it to the right hand edge as a single connector” Upton posited. “We’d also have a question about what we did with PCI Express . . . and that’s probably the obvious option to get something that has exposed PCI Express that isn’t a Compute Module.”
Upton explained it would be a challenge to keep a Raspberry Pi 4 Model A close to the same price point as the current Raspberry Pi 3A+, which currently retails for $25. If the price had to rise to $30 or more, he opined, most people just pay the extra few dollars to get the $35 Pi 4B.
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