Bert Freudenberg wrote:
> What we will never know is if the first Jitter had been incrementally  
> improved rather than being abandoned like all its successors, it may  
> have surpassed the current interpreter performance by far. The  
> downside is that it would inherently be much more complex - the  
> interpreter strikes a nice balance here.

The first jitter had the advantage of being cross-platform, but as I had
predicted it only improved performance by around 50% which is less than
what we got by making the interpreter better. The second jitter (known
as Jitter3) was actually finished as far as I can tell. There was still
some stuff to be done, but it was no worse in that regard than Unicode
or Traits support in current Squeak. There simply was not enough
interest for it to be adopted.

And since it was finished, you can download it (get Squeak 2.3) and run
some benchmarks (in Linux machines, at least). Here are the numbers on
this machine (3GHz Pentium 4):

2.3 image and normal 2.3 VM - 62,500,000 bytecodes/sec; 4,591,325
sends/sec
2.3 image and Jitter3 VM - 100,000,000 bytecodes/sec; 10,494,459
sends/sec
3.9 image and 3.7 VM - 160,602,258 bytecodes/sec; 7,292,693 sends/sec

The Jitter3 numbers varied wildly, but even the more stable numbers for
the normal 2.3 VM are very suspect. The problem is that the old image
didn't expect such a fast machine and doesn't seem to loop enough times.
But the point is that the code is out there and we can actually run it.

-- Jecel