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I am having overrun problems with a high-speed external modem and suspect it is because my COM ports do not have a 16550 UART. I need to find out if they do or not, and if not, what can be done about this
Explanation: You are experiencing overrun errors on an external modem, especially a faster modem attached to an older PC. This has been attributed to the fact that your PC's serial (COM) ports do not have a modern 16550 UART, which includes a 16-byte buffer to reduce the possibility of overruns. You need to find out what sort of UART you have and if you don't have a 16550, explore options for getting around this shortcoming in your system.
Diagnosis: Most newer PCs do have a 16550 UART, although many older ones do not. Using a high-speed modem on an older PC can depend on getting the newer UART so that the overrun problems are avoided. Fortunately, this is relatively straight-forward to do.
Warning: Do not attempt
to discern what the UART is by running MSD (Microsoft Diagnostics) from within a DOS
session under Windows. You can get incorrect results.