More render nodes and slower speeds !?

[Streetwise]

I am using two identical Render Nodes with 12-Cores each. I rendered out an image with that setup that took 3hrs. 45min @ 4096x3277. I have a spare 8-core MacPro running bootcamp and XP64 with 6GB RAM. When I add this machine to the mix, my render time actually increased to 4hrs, 5min!

Since the MAC render node is using 6-yr old technology, and the two identical nodes, less than a year old, is there something going on with the "farm" only being as fast as the slowest machine?
Are there any things I could do to try to speed things up? I would have expected faster times, not slower...

Thanks

Dave

[vlado]

It is odd indeed; if you look at the CPU usage on the nodes, are they running at 100%?

Best regards,
Vlado

[Streetwise]

Yes. All running at 100%. So adding a slower machine into the mix shouldn't slow everything down as in "No bucket left behind"... At least in theory?

[vlado]

No, ideally it should not slow things down. Perhaps we have to try and reproduce this here.

Best regards,
Vlado

[devin]

I don't think there's a problem, your faster machines will finish their buckets first and the slower one will take much longer to finish it's buckets. If it's six years older than your newer one's it's not surprising it's not helping your overall speed, your farm in this case really is as slow as your weakest machine.