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Old 06-14-2018, 11:09 AM   #1
mustgroove
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Default Render speed weirdness - iMac Pro rendering slower than MacBook Pro

I'm seeing some weirdness with render speeds in Reaper of late.

Every week I use Reaper to render out a 3-hour-long project, and getting it to render as quickly as possible is a priority when the deadline is getting tight, so I'm mindful of render performance. Sometimes I do this project while travelling (using a MacBook Pro), and sometimes I do it in my main studio (using an iMac Pro), so I'm often looking at the difference in render speed between these 2 machines.

Doing this week's project, I've noticed something weird - the iMac Pro renders slower than the MacBook Pro. Rendering the exact same project on both computers, with all plugins bypassed (there are only 2 plugins in total anyway), here's how the renders proceeded:

The iMac Pro slowly gets up to ~70x realtime render speed and stays there. The MacBook Pro gets to 70x realtime render speed way more quickly, and then keeps speeding up gradually to 75.5x realtime by the very end of the render, and looks like it would keep speeding up more if the project were longer.

The iMac Pro is barely breaking a sweat - fans aren't spinning up, CPU temp hasn't budged much. The MacBook Pro is being slammed, the CPU temp is quite high and the fans are going quite fast by the end of the render, but it's the MacBook Pro that's actually rendering faster.

In terms of CPU power, my iMac Pro (https://browser.geekbench.com/macs/425) blows my MacBook Pro (https://browser.geekbench.com/macs/344) out of the water in every regard. And again, these test renders were done with all plugins bypassed, so the entire project is just summing audio together.

I'm kinda baffled why this would be the case. I took Licecaps of the renders to show how they each progress:


iMac Pro:



MacBook Pro:
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Old 06-14-2018, 11:15 AM   #2
mustgroove
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Doing these renders again, the iMac Pro gives basically the same render speed every time, it's quite consistent - once it hits 70x (fairly slowly), it stays there.

Doing the MacBook Pro render again, this time it hit 76.2x by the very end of the render:

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Old 06-14-2018, 07:56 PM   #3
AkeW
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Different hard drive types maybe? Ssd in macbook and mechanical in mac pro?
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Old 06-15-2018, 07:08 AM   #4
mustgroove
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It's an iMac Pro, not a Mac Pro. Both machines have SSDs, and in both cases I'm rendering to the SSD.
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