Thursday, August 19, 2010

The Bad Old Days

Remember the bad old days when every PC adaptor card had jumpers for configuration settings? Today, I spent a few hours in that world again because the most common hardware bus used on embedded PCs is still PC/104 which, it so happens, is just the old PC ISA bus on a stackable connector.

I was configuring a PC/104 8 port serial board which required 64 consecutive I/O ports. I took more than a couple of hours to find that many consecutive ports on the particular SBC I was using. Sheesh!

I tried disabling some devices in the BIOS to free up some ports BIOS. Hahahaha! On this SBC, that trick doesn't actually disable the device physically, so you still get a port conflict. This SBC also used a number of undocumented ports for something or another.

I should point out that this is a 10 year old SBC which was not using its PCI bus correctly. The SBC used port mapped I/O instead of memory mapped I/O for the PCI devices like USB and sound. That poor design choice made the I/O map very cluttered, which of course, is one reason why port mapped I/O is deprecated for PCI devices.

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