KB4100347 Intel microcode updates for Windows 10 v1803 - January 8 Win Update

Oh well no real change in latency in my case anyhow.
All within tolerance.

andyouf said:

What is running in memory?

Please look at that post
The Microsoft provided microcode runs in RAM.

ddelo said:

Please look at that post
The Microsoft provided microcode runs in RAM.

Yes, it does, but the particular RAM in question isn't your PC's normal RAM, it is a small bit of RAM inside the CPU called the 'Writable Control Store' (WCS). And it is always stored and run from the CPU's WCS regardless of how it got written there, by the BIOS at POST or a .dll during OS boot up. The end result is identical, the microcode is inside the CPU.

Starting with the Pentium Pro in 1995, several Intel x86 CPUs have writable microcode.^[26][27] This, for example, has allowed bugs in the Intel Core 2 and Intel Xeon microcodes to be fixed by patching their microprograms, rather than requiring the entire chips to be replaced. A second prominent example is the set of microcode patches that Intel offered for improving the capabilities of processor architectures of up to nearly 10 years in age in the progress of counter fighting the serious Spectre and Meltdown security dangers as went really public in start of 2018.^[28][29] A microcode update can be installed by Linux,^[30] FreeBSD,^[31] Microsoft Windows,^[32] or the motherboard BIOS.^[33]

Microcode - Wikipedia

Bree said:

Yes, it does, but the particular RAM in question isn't your PC's normal RAM, it is a small bit of RAM inside the CPU called the 'Writable Control Store' (WCS). And it is always stored and run from the CPU's WCS regardless of how it got written there, by the BIOS at POST or a .dll during OS boot up. The end result is identical, the microcode is inside the CPU.

Microcode - Wikipedia

Thanks @Bree
Excellent technical explanation!

Ground Sloth said:

It now appears that KB4100347 wasn't actually updated. The Microsoft support web page associated with KB4100347 (which can be found in the first post) no longer says it was updated on 8/21; it has (at least for now) gone back to saying that it was last updated on 7/24.

That would explain why one of my machines got the 8/21 version just now, but checking for updates on the other didn't see it as required. That one had already had the 7/74 one previously.