When I delete the suitable µcodes from i.e. a MP2,1 that were contained for i.e. an E5150 or E5160 processor, or even when I delete all microcodes, and flash that back, the machine still boots!
What could be an explanation? Some backup copy of the last known-good µcode table in the Northbridge (4-8k is not so much to store anywhere)?
The CPU contains its own microcode!
Microcodes in firmware are errata. The processor should be perfectly capably of booting without getting any additional microcode at boot. If they could not, they should have never left the factory. Besides, operating systems contain their own version of microcode patches that are loaded into the CPU when the OS starts.
Checking for microcodes is an antifeature. The BIOS on many motherboards checks to see if they have a microcode for the installed processor and refuse to post or boot if no microcode is included. Evidently Macs do not do that. The iMac 7,1 is perfectly happy to boot with a Penryn processor it has never heard of. Unflashed Mac Pro 1,1s will happily run quad-core Clovertowns.
Does anyone know if the intel ME is located in the 5000 controller (Northbridge) and what kind of embedded controller intel used there? Or does it come along contained in the Xeons?
I believe there is some separate controller on the Intel S5000-series boards for system management. (A bit similar to the SMC on Macs.) The Intel firmware package actually contains three components, named BIOS, BMC, FRUSDR. One of these may be firmware for system management. (Don't ask me what the third one is ..). I think all three are included in the same 1,7 MB .bin file.
The Core microarchitecture used by Clovertown and Harpertown Xeons is the last Intel architecture without the infamous Intel Management Engine backdoor hidden in the chipset. That is why I believe there will always be an interest in these computers.
I have managed to find the firmware update for the Intel S5000 series servers boards. (Intel must have removed the file from their site since I first posted about this.) The latest BIOS version for the boards is R0098 from November 30, 2010. Only version R0096 from January 13, 2009 can be found anywhere on the web.
I actually managed to download firmware version R0098 from the Intel site last year when it was still available. The release notes contain this text:
BIOS Changes in release R0098.4
- Added Microcode Update - SRV_P_96 to address the following:
Intel(R) Xeon(R) Processor 5100 Series Specification Update, Erratum AG131
Intel(R) Xeon(R) Processor 5200 Series Specification Update, Erratum AY76
Intel(R) Xeon(R) Processor 5300 Series Specification Update, Erratum AJ127
Intel(R) Xeon(R) Processor 5400 Series Specification Update, Erratum AX76
The processor specification has changed, new microcode is needed to fix this issue. Intel has recently been updating microcodes to old processors to mitigate Meltdown and SPECTRE and other side-channel vulnerabilities. The Core 2 based Xeons have never received a fix. It may be that they are actually not vulnerable as they do not use hyperthreading.
Update July 30, 2020: The Intel .zip packages contain two versions of firmware, a .bin file and a .cap UEFI capsule file. I tried opening the files in both the R0096 and the R0098 firmware packages with UEFITool 28. UEFITool does not understand the .bin file. It can open a few levels of the .cap file until it reaches a FFSv2 volume it does not understand. The FFSv2 volume is 1969609 bytes but the freeform file inside is only 3345 bytes.