macOS Monterey 12.1 Beta 1 (21C5021h) and RDRAND requirement

[khronokernel]

With today's latest Beta, XNU now unconditionally requires all machines to have RDRAND support to boot. Because of this, all pre-Ivy Bridge Macs will no longer boot 12.1.

For the time being, users are advised to stay on 12.0.1 if their machine is Sandy Bridge or older.

Affected Macs:

• MacPro5,1 and older
• MacBook7,1 and older
• MacBookAir4,x and older
• MacBookPro8,x and older
• iMac12,x and older
• Macmini5,x and older
• Xserve3,1 and older

Work Arounds

Currently the only reliable work around is to use 12.0.1. Below we've provided a direct link as well as a mirror for when Apple drops 12.0.1 from the Software Catalog:

• InstallAssistant (Direct) - 12.0.1 (21A559)
• InstallAssistant (archive.org) - 12.0.1 (21A559)

References

• kernel 21C5021h (12.1)
• kernel 21A559 (12.0.1)

[khronokernel]

RDRAND Branch implements Syncretic's work around to this issue, unlikely to be merged into mainline till Beta 3+ to ensure XNU doesn't have any additional changes we need to account for:

• Implement RDRAND Patch for 12.1 Beta 1+ #671

[khronokernel]

Seeing as RC has not re-added the RDRAND code path, closing