I found this article on CCO which seems to say that a PC running SoftPhone needs to be connected to a Cat 6000 with PFC. If this correct? Can the PC be connected to a 3524, for example, in the closet which in turn is connected to a 6000 with PFC?
Some enterprises are deploying IP telephony using the Cisco SoftPhone application. In addition, there are many more enterprises that wish to evaluate the viability of using PC-based VoIP applications. Many PC network interface cards (NICs) do not currently set 802.1P CoS bits for Layer 2 classification. Even if the PCs did set Layer 2 frame markings, the vast majority of enterprise administrators would resist "trusting" a user's PC. Because of these factors, Cisco SoftPhone currently classifies voice packets only at the Layer 3 IP header. In fact, all voice bearer packets originating from the Cisco SoftPhone application are marked with an IP Precedence value of 5. Of course, this marking requires a wiring closet Ethernet switch that is Layer 3 enabled, with multiple queues, to correctly queue these voice packets. Currently, this limits Cisco SoftPhone designs to PCs connected to Catalyst 6000 switches with a Policy Feature Card (PFC) installed.