Since the 6504n broke the established pattern for security mode throughput, I hoped that it would also handle mixed clients (STAs) and neighboring legacy WLANs better than the competition. But, alas, that was not the case.
I set up my usual test using a second notebook with a Linksys WPC54G V3 11b/g card (Broadcom chipset). Both it and the Fujitsu notebook with the Edimax EW-7718Un adapter were associated with the 6504n, which was set to its 20 MHz Channel mode.
I then ran two IxChariot throughput.scr streams, alternating the STA that got on the air first. Figure 16 shows how uplink throughput was shared when the 11n pair started first, while Figure 17 shows the 11g pair starting first.
Figure 16: Mixed 11n, 11g STAs - Uplink, N starts first
The results show familiar behavior: the 11g STA gets knocked down a lot (3 Mbps, in this case), while the 11n STA takes about a 50% throughput hit.