Managing expectations

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1

My rig includes a GTX1070 8Gb gfx card, and as much as possible I render on GPU only.

Against the odds these days, I have a 2nd GTX1070 8Gb gfx card on the way (and I know, they are like hen’s teeth).

I bought this almost exclusively for Blender, but will probably also use the 2nd GPU as a passthrough for VirtualBox. The latter is irrelevant.

In Blender, can I expect a halving of rendering time by rendering on two GPUs?

EDIT - I know that the preparation (building bvh etc.) will not be improved. It is once the render actually starts that I’m interested in.

TIA

2

My understanding is that in those cases where you have two identical GPUs, you can expect to cut render times in half compared to using just one of them.

3

Thank you - I guess I’ll find out tomorrow when it arrives, assuming I don’t get a box of bricks instead.

I’ve benched a couple of scenes to test against.

4

I have two gtx 1070 ti’s (bought used, I’m not rich). Both 58 sec. One 113sec. So 1.95X speed on that test. Close enough to call it 2X.

5

OK - having got number 2, got fed up with crashing before I remember the BIOS reset and just re-enabling pushed my RAM back to 3Ghz (which it doesn’t like - 2933 is the sweet spot) I can confirm that actual render times, is double. The extra 5 - 10% Splododyne noticed is likely the pre-render prep.

I’m quite happy - probably better than a single 3900 series.