MP 1,1-5,1 Upgrade suggestions - Mac Pro mid 2012

[zzzachi]

you could buy a simple PCIe X4 adapter card e.g. KRYO EVO for ~ €30,-

i read misc comments about this... is it 100% sure that such a setup is really bootable?

@redfoxx
the gpu is a must (eg. RX580) optional is a better cpu (eg. 5690), ram, ssd or nvme
i'd hurry for the gpu, the availability goes down, prices are rising.

 

[KeesMacPro]

i read misc comments about this... is it 100% sure that such a setup is really bootable?

Yes it is, among uncountable others, I've been using these as well for the last years without any issue whatsoever.
The SATA bays on a cMP4,1/5,1 are SATA II, which is outdated and very slow compared to a NVMe blade.

Could you post a misc comment as an example?