EDIT2: Sorry about the mixup. The card I describe below does work in Mojave. I was playing with a couple of configurations and had switched to a non-working configuration. Prevously, I had incorrectly stated that the I/O Crest controller card worked OOB. I did need to install AHCI_3rdParty_SATA.kext. Attached is a screenshot showing performance of an old SanDisk SSD. Also attached is a screenshot showing how the card appears in System Report. I have corrected the text below to accurately reflect my configuration.
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I installed an "I/O Crest 4 Port SATA III PCI-e 2.0 x2 HyperDuo RAID Hard Drive Controller Card" based on the Marvell 9230 Chipset. I got the RAID version just to give me options (although I'm not sure the hardware RAID will work with Mojave). It was only $4 USD more than the non-RAID version. The card worked after installing AHCI_3rdParty_SATA.kext. It's a PCIe x2 card, so you'll get the full SATA III drive speed.
I am able to boot Mojave from drives connected to this card and I can use drives connected to this card as non-boot storage. I have not yet tried to use the hardware RAID capability of this card. I paid less than $33 USD for the card. My system configuration is as follows:
- Biostar TH55HD Socket 1156 Motherboard
- Xeon X3450 CPU overclocked 20%
- Mojave 10.14.6
- MacModel MacPro5,1
- CLOVER (Legacy) 5070