COM Test- Windows drops serial port

[DanB]

We see this sporadically on systems when testing (2) COM ports over an extended period of time (18-24hrs):

1) Testing starts and progresses as normal.
2) COM2 Error "The requested COM port could not be found."
3) Check device manager and COM2 port is not listed.
4) Right-click and 'scan for hardware changes' and COM2 reappears.
5) Restart BurninTest- COM2 fails (it is listed in device manager though)
6) Reboot and restart BurninTest- test starts and progresses as normal.

Noticed that the COM BurninTest tests appear to take turns when testing- COM1 tests while COM2 waits; COM2 tests while COM1 waits.

Could this 'wait time' during testing cause the Windows XP operating system to drop the idle COM port?

[Ian (PassMark)]

For the COM2 port to become not listed in device manager, the device driver has most likely been unloaded. I would suspect either a BIOS, hardware, or (less likely) a device driver problem.

Do you see the problem on different types of systems - different hardware and different BIOS and different OS's, or the same?

I would check that you have the latest version of BIOS for your system.

BurnInTest introduces a Wait (or delay) depending on the duty cycle setting at the end of each cycle (there is no delay introduced during the test if the duty cycle is set to 100). BurnInTest does not explicitly 'wait' for the alternate COM port to have a turn. Each serial port test is run in an independent test thread (with no explicit synchronization between them). The test may appear to take turns (i) due to a slightly staggered start of the tests and the time to run the tests being roughly equivalent -it could be worth trying to set duty cycle to 100 (ii) a lower layer (eg. Windows) blocks a thread on an operation.

Best regards,
Ian (Passmark)