I'm not after blazing speed, but if I pay an extra hundred bucks (Avnet tells me that is only another 10% of the base price) each for the "fast" family, I want the thing to perform at least as fast as the marketing guy says. That means 5 GHz count rates for a 64-bit synchronous presettable up/down counter, and much faster for the shorter ones. Now we know they can't do that ...

I also want to be able to attain 95% utilization 95% of the time. Most of the time that's not achievable either, at least in terms of marketing department gate counts.

Fortunately, the products I use are reusable, so once I find something I can use, I stick with it. That's why I use the Spartan-II stuff. It's 5-volt tolerant so I don't have to spend the extra $30 plus board space for level shifters. I most generally have kilowatts of power available, so the low-voltages stuff doesn't have any particular appeal.

THe clock-to-Q doesn't help since it's just latency at the chip boundary. The internal workings always have additional delays.

RE