This article contains information on an Ethernet issue which affected a small number of Power Macintosh 7200/90 computers.

Overview

Under certain network conditions, independent of the protocol being used, the Power Macintosh 7200/90 computer's built-in Ethernet port may fail to successfully send large packets over Ethernet.

Depending on the application or operation being performed, a user might experience one of the symptoms summarized below:

1. When using TCP as the transport protocol, the Power Macintosh 7200/90 may lock-up or timeout under certain conditions (for example, transferring a file to a UNIX host, or sending or composing messages from a Notes client to a Lotus Notes server).

2. Transferring or printing large files across certain repeaters may appear to cause the Power Macintosh 7200/90 to hang or may exhibit poor performance.

As of November 1995, Apple inventory of both service parts and newly manufactured computers are not affected by this issue.

Identification

If the Power Macintosh 7200/90 unit has a serial number of xx545xxxxxx or higher, then the computer should have the revised logic board installed.

If the Power Macintosh 7200/90 has a serial number of xx544xxxxxx then the computer MOST LIKELY has the revised logic board, but you should perform a visual inspection of the logic board using the Logic Board Identification instructions below.

If the Power Macintosh 7200/90 has a serial number of xx543xxxxxx or below then you will need to do a visual inspection of the logic board using the Logic Board Identification instructions below.

Troubleshooting

If you believe that you are experiencing difficulties related to this Ethernet jitter issue, we recommend that you try the following troubleshooting steps:

1. VERIFICATION

• Verify that you are using a Power Macintosh 7200/90.
• Verify that the unit is attached to an Ethernet network.

Does the problem occur on systems other than the Power Macintosh 7200/90 (preferably Power Macintosh 7200/75 to 9500 computers that use Apple's new Open Transport networking protocol)?

- If YES, then the problem may be related to the software or network that the unit is attached to. Perform basic software and network troubleshooting to narrow down the problem.

- If NO, then the problem may be related to Ethernet clock jitter. Refer to Logic Board Identification below to determine whether or not the logic board has been reworked. If the logic board has already been reworked then you may have a network problem. If the board has not been reworked then replace the main logic board in at least one of the systems to verify whether a reworked board resolves the problem.

Logic Board Identification

To identify whether a Power Macintosh 7200/90 logic board has been reworked is to look at location G1 on the main logic board. G1 is located next to the internal 50-pin SCSI connector and the CURIO ASIC.

If there is a 20MHz oscillator present at location G1 on the main logic board then the logic board has been reworked.

If no 20MHz oscillator is present (four blank solder pads) then the board has not been reworked.

IMPORTANT : If you contact (800) SOS-APPL for assistance with this issue, inform the engineer to reference Tech Info Library article, 18825 (an Apple-internal document).