PC Hardware in a Nutshell, 3rd Edition

Determining UART type

Under DOS and Windows 9X, you can determine the UART type with Microsoft Diagnostics (MSD.EXE), with a general-purpose diagnostic utility such as SiSoft Sandra, or with a dedicated port diagnostics program such as PortMaster. Either of the latter two utilities can be downloaded from any of numerous Internet sites.

Figure 22-3 shows SiSoft Sandra displaying information about COM1 on an AMD Duron system, built on a Microstar motherboard that uses a VIA KT133 chipset, and running Windows 98. Sandra reports that COM1 uses a National Semiconductor 16550AN UART, which is not precisely true. The COM1 UART is actually just one of the functions provided by the Super I/O portion of the Southbridge of the VIA chipset. The UART is emulated rather than physically present, but as far as Windows and connected serial devices are concerned, this system might just as well have a real physical 16550AN UART.

Figure 22-3. Using SiSoft Sandra Ports Information to view serial port configuration on a Windows 98 system

Utilities that run under Windows NT/2000/XP are limited in the amount and accuracy of the information they can provide because Windows masks the underlying hardware from the utility. For example, Figure 22-4 shows the results of running SiSoft Sandra Ports Information on a system running Windows NT 4. The Windows NT Hardware Abstraction Layer (HAL) prevents user-mode applications ...