@BrianK

We wouldn't sacrifice any PCI slots by assing USB as they would attach to the AMD8111 southbridge and use the spare PCI targets on that. PCI devices like that can normally master 6 targets, the reference board has 3, we could increase that to 4 to give the maximum number of expanion slots support by the ATX form factor (7 - 1xAGP, 2xPCI-X, 4xPCI) and use the other two targets for the USB and FW chips.
ATX may hve the room for the expansion but it's nice to provide these sorts fo features bult in, esspecailly if it is a high end board, then you can use all of those ports for whatever else you want. The size of an ATX boards allows for the extra features to be built in.
I certainly wont add these until the essential parts of the board are finished and tested on the prototypes. It's just good to diucsuss what features we want in advance, especailly as I don't really have anything else to do until we get the eval board.
I will read up on those chips alter when I have a chance.

@BrianK

IMHO it preferable to have as much as possible on board, so that I don't have to run around to buy a ton of extra cards. But of course there might be practical reasons for not doing so such as greatly added cost or complexety(ie will take ages to finish) of the board.

@On the subject of PCI-Express

I've done some looking around, and there are three "possible" solutions that I, as a layman, can think of.

1) Change the northbridge to one that supports PCI-Express. This is of course (sadly) not an option with the products on the market today.

2) Change the Hypertransport to PCI-X chip to a HT-to-PCI-E one. Sadly the problem with this one is that therer are no such chips on the market today. This of course doesn't mean that there might not be chips that do this on the horizon, unfortunately I don't know of any. (Might be a good idea to check around about this)

3) Use a PCI-Express southbride. Now one of the special things about PCI-Express is that you don't have to use 16x connection to a 16x slot, you can use a x8 or even, say, a x2 one. This is because the graphics card will adapt itself to the available amount of lanes. There might be a problem with some kind of mecanism that prevents it from working unless there is a minimum amount of lanes available. But I've not been able to find anything on if there exists such limitations. Unfortunately this is allso not an option (I think), as the SIS 965(L) and the upcomming VIA VT8251 both use aproprietary interconnect to communicate with the respective northbridges.