It depends on your version. 6.3 might allow you to use 100megabit FDX on both interfaces. I believe before this change 10 megabit FDX was the limit. I believe cisco now says that the 506e can do 60 megabit of clear text throughput. You always have been able to hard code auto/full or half duplex, but now speed should be an option too.
Note that the above may be all wrong ;-) - the pix os 6.3 release notes only refer to these changes for 501 and *506e* - I have no idea what happens on a old 506 as I haven't upgraded one yet.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...