Update: The Compute Module 4S is now listed on Raspberry Pi's website. But they state it "is not for general sale."
Strange times beget strange things.
And that's an apt description of the new Raspberry Pi Compute Module 4S:
The above chart is from Revolution Pi's page announcing the RevPi S and SE, which are updates to their popular CM3+-based industrial DIN rail computers.
They've been working on a RevPi 4 built around the Compute Module 4 that was announced in 2020, but after many delays, it seems they brokered a deal with Raspberry Pi to use a cut down Compute Module 4S, which eschews not features like gigabit Ethernet and PCI Express, as well as the entire form factor of the CM4.
The CM4S mashes a BCM2711 SoC into the Compute Module 1, 3, and 3+ form factor—which was used for years until the switch to 2x 100-pin board-to-board connectors on the CM4 (pictured on the left):
I'm guessing the reason this board was produced is because Raspberry Pi can't secure enough of the older 40nm process SoCs that powered older-generation Pis.
Instead of leaving industrial customers who designed around the old SO-DIMM form factor out to dry, they updated the design to use the 28nm BCM2711, which does seem to be available in quantities surpassing 500,000 per month currently.
So far, I don't know if the CM4S will be made available to anyone outside of Revolution Pi, though I've posted on the forum asking as much: New Compute Module 4S? [Raspberry Pi Forums].
While the CM3+ and earlier Compute Module models weren't quite as popular as the CM4 is today (owing to their slower SoCs and weaker IO), they are in a lot of embedded devices. I'm sure many customers would love a drop-in upgrade to the BCM2711, with it's doubled CPU performance, faster GPU, and doubled memory bandwidth.
For a little more detail on the CM4S, check out my latest YouTube video, embedded below: