Love this PPL metric! Got me to sign up to this site.

Can I suggest a slight change to how the calculations are done? Currently, the performance scores are a simple multiplication which will be biased based towards either cpu or gpu depending on the scale. Using the geometric mean instead will normalize the range of the values so that cpu and gpu performance is equally weighted regardless of the scale used.

Current: ((CPU*GPU)/(Volume^1.5))/100

Geometric mean: ((CPU*GPU)^0.5/(Volume^1.5))

You won't have to divide by 100 also. I'm guessing the cinebench and time spy was chosen as they had somewhat similar number ranges. Using the geometric mean, will give you a better unbiased weighting between cpu and gpu performance. It'll also give you the freedom to use any other benchmark with widely different number ranges without bias towards either the cpu or gpu.

Multiplication already balances CPU and GPU measures. No need to take a square-root there. Not saying it's wrong but it brings nothing to the table.

Plus, going with your formulation, volume becomes much much more important. Your ranking is equivalent to

((CPU*GPU)/(Volume^3))/100

Compared to the current ranking, it makes the volume dominate. Is this desirable? I'm not sure. I mean there can be an argument to make volume more prominent than it is now but even then, I would recommend going for a power of 2 instead of 3. So it'd be like:

((CPU*GPU)/(Volume^2))/100

Or, if we go with your approach, it can be

((CPU*GPU)^0.5/(Volume))

They're equivalent, ranking-wise...

EDIT: I believe it is fine as it is now. Increasing the power of the Volume takes away from the definition of SFF, if by SFF we're talking about sub-20 liters. Another argument can be even to reduce the power of Volume from 1.5... Volume in itself is a cubic measure (mm^3, etc.) so why further increase its exponent?

EDIT 2: Now that I started thinking about this, I gave it a good thought... I really believe taking Volume to a higher exponent than 1 takes away from the PPL measure: it must be (CPU*GPU/Volume) as it was originally. Any power other than 1 is simply arbitrary and it rewards micro-FF systems for no reason. PPL = performance per liter after all

CPU and GPU performance benchmarks can evolve over time, of course, and it needs to be debated whether the current benchmarks (CB20 and TimeSpyGFX) are the best ones... One idea can be to use two CPU benchmarks and two GPU benchmarks (and possibly take a geometric mean at that point).