At a high-level, I think what you are saying is true. I've not
done a GMII
interface as all of my GigE experience to date has been fiber.
However, I
think the GMII interface is 8-bits wide (as opposed to 4-bits wide
for MII),
and a GMII runs synchronous to a 125MHz clock (as opposed to

or 25MHz
for MII). Seems like there would be a lot of issues to work out in
scaling
multiple 10/100 MACs to act a Gig MAC. CRC checking is the first
thing that
comes to mind, MAC address comparison (checking for broadcast

addresses, etc.) is another issue that would seem difficult to do without substantial interaction between the MAC "sections." I don't know your application, but I would think that you have to be very close (if not over) a cost/performance crossover point such that you could just go buy a Gig MAC/PHY and hardwire it to run like you want (granted, a lot of the MACs will probably have a PCI interface on the host side, which may or may not add un-needed complexity to your architecture). Just some thoughts from someone who knows zero about your specific application. Regards, Kevin -----Original Message----- From: owner-ethmac@o... [mailto:owner-ethmac@o... ]On Behalf Of Colin Sent: Thursday, August 01, 2002 9:01 AM To: ethmac@o... Subject: [ethmac] MAC Rx architecture Having got some great feedback on this forum already, I'd like to ask another question - one which I've been pondering for a couple of days now: If the functionality of the MAC Receiver for GigMAC is basically the same as for Fast Ethernet (full-duplex only), what is the difference in the resulting hardware architecture? Is it simply that for GigMAC the hardware must operate faster to handle the faster arrival of data? Or would a completely different approach be required? I've thought about using an arbiter with multiple instantiations of Fast Ethernet MAC Rx units to acheive Gigabit throughput as an option. At the moment though I'm trying to go with a single rx unit operating extremely quickly. Any thoughts? Cheers, Colin