UX/UG/UR models are generally a pain to maintain. As soon as you import one change the capacitors in the CRT PSU card and Computer PSU card or you'll be in a world of pain. The U* models have a removable plate on the right side to insert a RAM card. Stock they all come with 2MB of RAM and you may add a maximum of 8MB ram card for a total of 10MB.
The U* models also can function as monitors for other FM Towns computers. There is an output for RGB on the rear towards the bottom if you wanted to feed it into a capture device or other monitor in case yours is dead.
There is also RGB input port towards the upper right side. Slide the switch to have internal or external display. I've also seen some U* models in Japan with a video card and a DB15 cable feeding it BACK into the CRT input permanently outputting 15khz.
UX model. 386SX at 16mhz
UG Model. Notice the FAST mode light on the front. It also says FM TOWNS II on CD rom drive. 386SX at 20mhz
UR Model Notice the FAST mode light on the front and say UR on disc drive. Has 486SX
U*40 and U*80 models have an internal SCSI connector for their mechanical hard drives that are dead or about to die. Base U* models without an internal hard drive don't have this connector and it's impossible to add an internal HDD. You can only use an external hard drive for those models with a SCSI ID of 1 or higher.
