I think the problem is 10.14.5 and 10.14.6: Results drop significantly after upgrading from 10.14.3
and in my case restored by downgrading to 10.14.4
I found your thread the other night, after upgrading from 10.14.3 to 10.14.6 and then pulling many hairs out when results in Geekbench 4 dropped to 130k from 180k.
https://browser.geekbench.com/v4/compute/compare/4564606?baseline=4564603
Installing 10.14 over the top restores the speed to 184k, although the fan just runs.
https://browser.geekbench.com/v4/compute/compare/4564606?baseline=4568326
As noted at the beginning, still works after 10.14.4 combo update.
However, not interested in doing the 10.14.5 (if some other brave soul wants to test, its fine, I am on an NVME and since my hack only has one PCIe, I can’t test). The odd part is that this path 10.14 with combo pack 10.14.4 leaves the fans spinning faster, than the quiet of the 10.14.3 direct install. I am planning to try a 10.14.3 install again over the top.
I have a Vega 64 Sapphire HB2
currently in cMP 4,1-5,1 (w/ Crucial 1tb NVME and 96gb 1333 ram)
Already was sad that the Vega64 does better on my hack
(but need the 96g Ram of the cMP; and the extra PCIe for the NVMe)
Vega on the cMP takes a hit for being PCIe 2.0 instead of 3.0 // and for the 1600mhz ram
this can be seen in results of Hack vs 10.13.3
https://browser.geekbench.com/v4/compute/compare/3800953?baseline=4564603
Hack
iMac late 2012 - 21.5
GA-H77N-WIFI/16GB/i7-3770s/Samsung Evo 850
To control for upgrade to new Bootrom 140.0.0.0 vs 144.0.0.0
Retested in High Sierra…
New bootrom, seems to be a bit better; and HS has a bit of an edge over Mojave.
However, 187k vs 185k ~ same good results much better than the 10.14.6 130k.
Should note, also tried replacing the AMD10000Controller.kext (disabling SIP, and then sudo touch /System/Library/Extensions/ && sudo kextcache -u /) on 10.14.6 before doing the install of 10.14, and couldn't get it to recognize the Vega64. Putting back in the old trusty Nvidia GeForce GT 120; allowed booting 10.14.6 with the kext from 10.14.3 to see the Vega wasn't loading a driver.
To rollback, booted to 10.13.6 on separate SSD, and did the install of Mojave 10.14 again on crucial NVME.