On modern systems, there's a "base clock" (often shortened to "BCLK") from which all other clock rates on the motherboard are derived. This base clock is almost always nominally 100 MHz, as that provides a nice round number for multipliers to work from. Meaningful overclocking using the base clock is almost impossible, though, because devices like SATA controllers, USB controllers, and PCIe cards really don't like being overclocked. Most boards won't tolerate being more than just a couple of MHz out of spec before components start giving up the ghost. An Australian brand crystal shop introduce nn extra 100 Mhz of CPU clock isn't enough to warrant making your system flakey, so generally, people don't bother with BCLK overclocking anymore.
There are exceptions to this, though. Some motherboards come equipped with extra clock generators for specific components so that you can overclock your "BCLK" without affecting the clock rates for other components. This has the advantage of allowing you to overclock processors that are, in theory, locked from overclocking.
We've already seen this done to fantastic effect with current-generation Alder Lake processors; champion overclocker Der8auer took a Core i5-12400 up to 5.2 GHz all-core—the same clock rate that the Core i9-12900K hits on a single core. This is, obviously, a ludicrous value in terms of price-vs-performance, but there's a catch: he was using a pricey ASUS ROG Maximus Z690 Apex motherboard.
Indeed, there really isn't a shortage of motherboards that include these capabilities, but they're overwhelmingly parts that occupy the higher price tiers. That makes BCLK overclocking more of a novelty, as those boards are likely to be paired with high-end "K"-series processors that are unlocked for overclocking—and so fast that they don't really need it, anyway.
The tweet reveals the details of an upcoming MSI motherboard purportedly to be named "MAG B660M Mortar MAX WIFI DDR4". This is an Intel LGA 1700 motherboard for Alder Lake (and presumably Raptor Lake) CPUs that sports a low-cost B660 chipset, DDR4 memory support, and Wi-Fi 6E—as well as an integrated clock generator for BCLK overclocking.This motherboard is actually a revised version of the MAG B660M Mortar WIFI DDR4 (note the lack of "MAX"). Aside from the OC Engine feature, it also includes PCIe 5.0 support for the main graphics card slot, 2.5 Gigabit Ethernet, and HDMI 2.1 for the CPU's integrated graphics. All in all it looks like quite a fine motherboard. We don't know how much it'll will run, but it's sure to be cheaper than the high-end Z690 models that you would have had to buy to get BCLK overclocking support. Chi11eddog says the board will be available in July.