Over the weekend I built a specially optimized version of the client (with SSE2 instructions enabled, incase you're curious). It's good for version 1.23.4 only. Offline around Antwerp in a Daimler it bumps me from 70fps to 130-140fps. Online it's not quite so dramatic but still noticeable. We're contemplating a dual-build so that players with SSE2 capable machines can take advantage of these extra instruction sets.
Why not just plain old SSE to hit more CPUs? Well, it would certainly give some performance boost, but SSE2 makes some actual use of those extra 64 bits lying around on the 64bit CPUs so the improvement really justifies the overhead. I'm not sure whether plain SSE does without some coding specifically for it.
I got a bunch of tasks done today that were supposed to have been done last week but have been stopped by CTHL work. None of which I'm going to detail because they'd probably make anyone stuck with CTHLs cry – but there wasn't anything I could do today CTHL related (other than continuing to try to get more data, which naturally I did). We're still working on those outstanding CTHLs but its a matter of trying to find commonalities. Nothing obvious or evident is causing it. And nothing I could work on solidly today.