Dismiss
There will be a system update on Friday, May 5th, 6 PM ET. You may experience a brief service interruption.
Browse Prior Art Database

Method for implicit transmit completion indication

IP.com Disclosure Number: IPCOM000008129D
Publication Date: 2002-May-20
Document File: 2 page(s) / 78K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for implicit transmit completion indication. Benefits include improved performance.

This text was extracted from a Microsoft Word document.
This is the abbreviated version, containing approximately 50% of the total text.

Method for implicit transmit completion indication

Disclosed is a method for implicit transmit completion indication. Benefits include improved performance.

Background

              Conventional high-speed I/O controllers, such as gigabit Ethernet message authentication controllers (MACs) are often through-put limited by the system bus. Any innovation that improves bus efficiency improves throughput.

              For MAC transmit operations, conventional bus activity typically consists of:

1.      Write to the controller to inform it that new transmit descriptors are ready

2.      Read of the descriptor(s)

3.      Read of the packet to be transmitted

4.      Completion write to indicate which operation(s) are complete

5.      Interrupt to alert device driver of completed operation

              These steps can be generalized to most operations that are initiated by software for a controller to complete. Of these steps, only step 3 transfers data for the operation. All other bus activity is control for the operation and is, therefore, overhead that reduces the bus efficiency (in terms of real data transfer).

              Two conventional methods for the device driver determine which transmit commands have been completed. The first method is to request that the MAC write back a completion indication when command execution is finished (step 4 above). The second method is to periodically read a control value from the MAC.

Description

              The disclosed method is a just-in-time transmit interrupt of the gigabit MAC. Using this interrupt, the device driver can determine which transmit commands have been completed without the use of completion status write-backs or reading a task index from the MAC. Eliminating these bus accesses improves the MACs bus efficiency and can improve throughput, which is especially important with dual-MAC parts.

              The just-in-time transmit interrupt enables the device driver to batch task assignments to the MAC, reducing overhead.

              Commands are issued to the MAC by filling out transmit descriptors and writing to a contr...