Grammar mavens: sped up or speeded up?

[Dilbertian]

Which is correct, and why?

You have speeded up the process.

Or

You have sped up the process.

I think 'speeded' refers to 'process' (the object?), whereas 'sped' refers to 'I' (the subject?).

Sped... Speeded is child's language AFAIK

Whichever one you prefer is 'correct'.
However sped sounds better to me.
In fact there are no rules. English grammar is descriptive not prescriptive. ..

Sped.

So what has happened to 'the process'?

The process has been speeded up.

or

The process has been sped up.

The process has been made faster.

I don't think you can use speeding up in that context.

Accelerated?

You have accelerated the process.
They process has been accelerated.

I agree with your first post, @Dilbertian, although I'd say it was more the case that 'sped' means 'went faster' and 'speeded' means 'made go faster'.

Similarly, 'shone' and 'shined' are both used, but not interchangeable. 'Shone' means 'gave off light' and 'shined' means 'made shiny.' So the sun shone, but he shined his shoes.

Sped up