Messages in this thread | | | Date | Fri, 15 Sep 2000 16:41:53 -0400 (EDT) | From | Donald Becker <> |
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On Fri, 15 Sep 2000, Bogdan Costescu wrote:
> On Fri, 15 Sep 2000, jamal wrote: > > You use the period(5-10micros), while waiting > > for full packet arrival, to make the route decision (lookup etc). > > i.e this will allow for a better FF; it will not offload things. > > Just that you span several layers by doing this, it's not driver specific > anymore.
Many chips have some sort of early-Rx feature, but it's still a bad idea for the many reasons I've pointed out before.
An additional reason not use early-Rx is that chips such as the 3c905C are most efficient at using the PCI bus when transfering a whole packet in a single PCI burst (plus two smaller bursts initially reading and later writing the descriptor). Using an early-Rx interrupt scheme means using multiple smaller bursts.
The early-Rx scheme worked well on the ISA bus, where transfers were slow and not bursting.
Also note: it is possible to drop an Rx packet after the early Rx interrupt.
Donald Becker becker@scyld.com Scyld Computing Corporation http://www.scyld.com 410 Severn Ave. Suite 210 Beowulf-II Cluster Distribution Annapolis MD 21403
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