Shouldn't make too much of a difference. Using Anandtech bench, the SYSMark performance difference between a 940 (3.0GHz) and 955 (3.2GHz) is 7.1%. The difference between a 955 (3.2GHz) and 965 (3.4GHz) is 5.1%. The difference between a 940 and a 920 (2.8GHz), which both have 3600 HT, is 5.2%. So there's a consistent enough performance to say that it's just another 2% slower.
The math would put it just under 100MHz slower per clock than a 945 with the full hypertransport. So if you want your 940 to compete with a stock 945, for example, you'd want to OC it to 3.1GHz (slightly less probably). It's still faster per clock than Athlon IIs. 940 (3.0GHz) is 11.6% faster than a faster clocked Athlon II X4 645 (3.1GHz).
The stat whore in me has spoken...