From MozillaZine Knowledge Base

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Thunderbird 1.0.7 doesn't appear to have any problems running on a dual core CPU such as a AMD Athlon 64 X2, Intel Pentium D, or Intel Pentium Extreme Edition. Thunderbird 1.5.0 and 1.5.0.1, however, have a bug where your connection may occasionally or even constantly timeout if you're using a dual core CPU. This may occur for IMAP, SMTP, and POP3 server connections. The recommended way of fixing this issue is to upgrade to 1.5.0.2 or the latest 1.5.0.x release.

The first step is to confirm whether its a dual core specific problem or not.

1. Try running Thunderbird in safe mode to temporarily disable any added extensions/themes.
2. Try increasing the connection timeout from 60 seconds to 120 seconds in Tools -> Options -> Advanced -> General.

If the problem still occurs download the nspr4.dll file and save it to the C:\Program Files\Mozilla Thunderbird directory, overwriting the existing file. This fix was added to Thunderbird 1.5.0.2 and later. It is recommended that you upgrade to the latest 1.5.0.x release as a permanent resolution to these timeout issues.

Alternative solutions:

1. Download imagecfg.exe and read the instructions on that web site on how to permanently bind a application to one core (run Thunderbird on only one of the cores). Supposedly that tool is also available from the Windows 2000 or Windows XP Server Resource Kit.
2. Manually modify the "boot.ini" file to use the /usepmtimer switch.
3. Install the AMD Athlon™ 64 X2 Dual Core Processor Driver for Windows XP and Windows Server 2003 . The setup program will add the /usepmtimer switch to your boot.ini file.
4. Modify your shortcut to use a launch program such as RunFirst to run Thunderbird on the first core/processor.
5. Decreased performance or unexpected behavior due to power management features can occur on dual core machines using XP SP2. It seems unlikely, but possible, this could cause a timeout.

If you're uncomfortable installing the Thunderbird patch installing the AMD driver or using a seperate launcher is the most user friendly solution.

See also

• Changing settings using about:config

External links

• Bug report for POP connection timeout on a dual core system
• Bug report for IMAP connection timeout on a dual core system
• Microsoft article on how to add the /usepmtimer switch