Coffee time for iMac 2017

[crazy frog]

So on PC with skylake/kaby lake chipsets it’s possible to modify a downloaded bios to work with coffee lake CPUs which all share the same 1151 socket. Has any such work been done with iMac 2017 to patch the bios?
it’s generally much better to run a basic i5 9400 than a i5 6500 or even a 7700k in my 2017 iMac.

 

[WarthogARJ]

I was just looking at this after I was inspired by an iFixit query.

From my research, it seemed that there are some quite fundamental differences between the LGA 1151 rev1 socket/chipset z170 used on the iMac 2017 with Skylake/Kirby CPU's, and the LGA 1151 rev2/chipset z370 used on the iMac 2019 with Coffee Lake CPU's:
- LGA 1151 rev1 1 vs rev2: pin allocations not same, even though mechanically one could plug an i5 9400 or even i9 into a 2017 socket
- Chipsets: the z170 and z370 are REALLY different. I cannot see a CPU designed to run on one being able to use the other one. And Intel says exactly that.
LGA 1151 rev1 vs rev2
Intel Chipsets
Data sheet z370

These refs mention that the intervening z270 chipset is (very?) similar to the z370, but the z170 is VERY different, and I'd think the reason why you cannot upgrade to CoffeeLake on a rev1 LGA1151 with z170.

So I think it's not just a bios issue: in any event, it seems pretty hard to address these issues by the bios.
And I believe that the EFI in both cases is different: so you'd need to address that.
Maybe flash the EFI chip?

Can you post the details of where it was actually done on a PC? As in run a Coffee Lake on an LGA Socket rev1?
And how did they know it really WAS a rev1/z170 chipset?
Although, Intel says z170/z370 are not backwards/forwards compatible, so it shouldn't really matter if they actually knew which it was.