Here's the system specifications for my IBM XT:
8088 Processor
640k of Random Access Memory, aka RAM
8-bit Memory Expansion card
21 Megabyte hard drive
CGA/MONO switch able video card
Parallel/Serial card
Second Parallel Port (On Memory Expansion card)
MS-DOS 6.0
Tandy EGA Monitor
About the innerworkings of the XT
Please note that there is NO CMOS setup, I've run into questions about that a lot. Hardware is defined by DIP switches on the motherboard. DIP switch settings can be found at: http://uncreativelabs.net/hwinfo/xtdip.htm
The IBM XT was released in 1983 after the IBM PC. The abbreviation "XT" stands for "eXtended Technology". One of the major features of the XT was the hard drive. Not many IBM PCs (IBM 5150's) have hard drives, and none were sold from with them from the factory. Being able to save a few megabytes in one place may seem meaningless now, but at the time the XT was produced, DOS was happy running in systems with 128k of RAM. Just part of the windows GUI takes much more memory than that.
The XTs had a limited number of interrupt requests (IRQs), with only 8. By the time the important system devices were installed, you had 2 or 3 free IRQs that were often used by serial or parallel ports for printers, modems, or other communication devices.
Hardware of the XT
The case was made of very solid materials. It's metal and plastic, and very strong. One person suggested that you could even drop it down the stairs and the computer would still work. (Don't try it!) Compare this to the systems that are produced now, and you can see why this particular system is loved by many. It's nice to be able to take off the case and not have to worry about breaking it.
The keyboard for the XT and PCs are special. They are incompatible with newer keyboards, and vice-versa. The best thing about the keyboard is like the newer IBM Model M keyboards, they're hard to destroy, and give you a solid noise when you press a key down. None of this quiet "touch typing" where you don't know if you even pressed the key down far enough to produce a letter. I have to say the noise, while irritating to some, is quite addictive.
Many people have either an IBM 5151 monochrome monitor or IBM 5153 CGA monitor for their XT. I have used both, but don't own either. What I loved about the 5151 was when playing Nibbles in QBasic, the tail would gradually fade out. The 5153 was color, but didn't match the resolution of the 5151, but sold anyway because it was color.
At the time of production of the XT, computers were so expensive that the system itself was all that someone could afford. There are other upgrade options like Sound cards, but they're usually found in XTs upgraded after Pentiums processors came out.
Here's the system specifications for my IBM XT: