Can I add an 8087 math coprocessor to the PCjr?
Yes. There is no socket on the motherboard for the 8087, so you just can’t plug the chip in. A company named TIAC Manufacturing (from Canada) made a daughterboard that used the 8088 socket, and had the 8088 and 8087 sit on the daughterboard. You will need to find one of these (or construct one!) to add an 8087 math coprocessor. The original cost of the TIAC jr-87 in late 1984 was $90, without the 8087 chip. Legacy technologies also made an 8087 daughterboard. Be aware that you may be stymied by software. An 8087 on a PCjr would be extremely rare, and if the software recognizes that it is running on a PCjr it may not even bother to look for an 8087. (A Racore PC ID cartridge could get around a software limitation like that.) You will have to run a program to change the equipment word in memory to note the presence of an 8087, as the PCjr BIOS won’t look for one and won’t set the equipment word right if one is present.
