Reaper's CPU usage Exponentially Higher Than Other DAWs?

[JamesG5454]

Hi There -

Here are my specs -
Mac Pro (Early 2009)
Dual Quad Core Intel Xeon - 2 X 2.93
24GB 1066 MHz Ram
SSD Startup Disk

Issue: Reaper's CPU usage is exponentially higher than other DAWs with the same project setup (Bitwig, Ableton, Studio One, and Cubase) ? I feel like I have clicked and unclicked every parameter that relates to Reaper's processing engine, and yet nothing seems to have a large effect on the CPU usage.

Question: Does anyone have an idea of what could be causing the issue. Or has anyone been able to tweak the preferences within Reaper so it functions efficiently on an old Mac Pro? If so could you possibly share the settings?

Thanks for any help you can provide,