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Wednesday, June 29, 2011

Overcoming fear of working on computer hardware

There was a point when I was not comfortable opening up computers to do things with their innards. One day, my dad took a chance and let me make a change to his very expensive system, and that set the stage for many good things which followed.

We had a computer which had your standard no-frills serial port, and a relatively interesting modem behind it. Trouble is, you couldn't actually use our modem at speeds much above 4800 bps or so, since things would get corrupted. I did my research and learned about UARTs and buffers and all of that mess.

What I learned is probably common knowledge for anyone who dealt with modems for about ten years there: the 8250 was just not suitable for high-speed communications. The amazing part is that you could get a replacement, the 16550AFN, and it was pin-compatible! I just needed to buy one and drop it in, but before that, I had to convince him that I would not blow up his very expensive machine.

I collected data and made my case, and he agreed. We made a special trip down to EPO (Electronic Parts Outlet) and bought what turned out to be the last one they had. Back home, I powered things down, cracked the case, and pulled the board. Sure enough, both chips were the same size, had the same number of pins, and all of that. I just needed to swap them.

It took some fiddling with a screwdriver to convince that socketed chip to come loose, but it did. It took even more fooling around with just the right amounts of pressure and folding of pins to make its replacement drop in. Once this was done, I put it back together, threw the power switch, and stood back.

Nothing caught fire. It did the usual tick-tick-tick-tick memory counting business, floppy drive seeks, and BEEP! DOS came up a bit later, and my terminal program confirmed: 16550AFN UART! I cranked up its DTE speed and tried a call. "CONNECT 14400/ARQ/HST/HST/V42BIS" was my reward, and things started moving ridiculously quickly.

That was my first experience working with bare computer hardware but it would not be my last. Thanks, dad.