I have Call of Duty 4 Modern Warfare on Sierra, ElCapitan external clones with High Sierra

Hi All!

I have Call of Duty 4 Modern Warfare on one Sierra (firewire), and one ElCapitan(USB) external clones and it plays fine on BOTH yet with the same game on the internal HD (SATA) which is fine according to TechToolPro v9.6 and Apples Disk Utility it's playing choppy in a High Sierra install.

specs of iMac

Model Name:iMac Model Identifier: iMac12,2

Processor Name: Intel Core i7

Processor Speed: 3.4 GHz,

Sys memory 16G

Number of Processors: 1

Total Number of Cores: 4

I've uninstalled COD already and reinstalled from the Apple store. Any solutions?

I really appreciate your looking at this and your time into answering.

Robert

nyc