Monday, 22 August 2016

Good News is No News

I'm still perplexed, but I do have some 'good' news. I had a typo that resulted in the main loop attempting to smooth the frame rate when profiling was enabled, when it should have been disabled.

So my frame rate for 'empty' screens is actually up around 43fps (not 29fps). Of course on 'busy' screens the frame rate smoothing logic did nothing so it's still limping along around 7-8fps.

What has me completely bamboozled is the fact that disabling the Z-order calculations still results in no more than 1fps improvement (and I had my hopes up when I first saw the above-mentioned typo), whilst another porter (to 6502) has seen significant improvement by optimising the Z-order algorithm. This means either the 6809 code is vastly more efficient than the translated 6502 code or, more likely, I've done something brain-dead in my attempt to circumvent it.

Oh and I think I saw some transient pixel corruption on one of the animated screens... perhaps that's a clue to something I've done wrong, or perhaps only a side-effect of disabling the Z-order calculations - I'm not sure.

So my quest continues to find the bottleneck on busier screens...

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