The last time I did a software upgrade on a TIU, it was a creaky Pentium III running Windows XP on only 256mb of RAM--the maximum that particular model could run. It did so much disk swapping (owing to the above lack of RAM) that it took several hours just to install/upgrade the .NET addon that allows the DCS software to function.
Why use such an antiquated system? It was the newest laptop I had on hand with an actual serial port, and I had tired of fiddling with the USB-serial converter I had bought for my netbook (later I found there was a driver CD in the package that needed to be installed before the cable would function) But once that was all said and done, the actual upgrade proceeded painlessly (once I properly seated the serial cable in the TIU--the cable came with a pair of bolts in the plug that had to be removed before it could make actual electrical contact.)
So the standards are pretty low. Low enough that you could probably use a laptop that is too slow to be usable for typical applications.
---PCJ