FIX FOUND: make coreboot compile and POST for D8 on coreboot 4.6: putting this here cuz lb issue list is very big and don't want this lost. will also post it on libreboot tracker

if (pDCTstat->Status & (1 << SB_Registered)) misc2 |= 1 << SubMemclkRegDly;

after

misc2 |= ((cs_mux_45 & 0x1) << 26);

in line 74 in the file src/northbridge/amd/amdmct/mct_ddr3/mctproc.c

according to comment on this reddit thread:

https://www.reddit.com/r/coreboot/comments/jdcn5y/latest_coreboot_for_the_asus_kcmad8/

According to that person, it was 610d1c67b2 commit ID in coreboot that broke D8 booting before it was removed in coreboot later on. the commit is here on reddit (the commit that broke booting): https://review.coreboot.org/c/coreboot/+/18369

the fix above probably also works for D16 aswell.

I'm probing the redditor for more information.

So:

coreboot commit fec8872c9d fixed RDIMM training stuff

coreboot commit 610d1c67b2 reverted the above commit

so when coreboot broke, per most user testing and automated coreboot testing, the board might have been affected by rdimm training, and had rdimm modules (registered modules, not unregistered like on consumer boards)

commit 10d1c67b2298a9840681c2b4492b6d3fdf44a46 is fixing a condition where if 8 DIMMs are used on a single CPU, or 8 each on 2 CPUs, "MC4 failures" occured and caused problems booting

well: fec8872c9d is in libreboot's version of coreboot

with just fec8872c9d but not the commit (see above) that reverted it, you can only use up to 4 modules per CPU on a D16.

...

and by reverting 10d1c67b2298a9840681c2b4492b6d3fdf44a46, D16 boots again in coreboot.

TODO then:

Find the commit that removed D16/D8 support from coreboot, and use that as a revision in libreboot for D16.

Now with that fix applied, then add whatever is needed to get D8/D16 boards back into coreboot.

I'm probably gonna add D16 in retroboot aswell, so that I can put microcode in the ROMs (because retroboot doesn't exclude blobs) so that opteron 6300 CPUs work well.

#12 FIX FOUND: make coreboot compile and POST for D8 on coreboot 4.6: putting this here cuz lb issue list is very big and don't want this lost. will also post it on libreboot tracker