FreeDOS should run on all PC hardware, even the IBM PC-XT and systems with as little as 640k memory. On newer computers, FreeDOS still works well with the latest CPUs, but in 16-bit mode. However, you may experience hardware compatibility problems on really old computers. Mark Aitchison lists a few systems that are known to have issues with FreeDOS:
- "Cyrix 486DLC CPUs (made by Texas Instruments) cause trouble for many systems, but I’m not sure of the details. (I do have a DLC I can get my hands on to test, though)."
- "Sanyo MBC 500 series computers are extremely incompatible in most ways; the BIOS only partially matches IBM PCs but the memory map, video hardware, etc are very different. The MBC 750 series is a bit more compatible, I heard."
- "Data General DG10 - this is a desktop minicomputer with DG’s own microEclipse CPU and an 8086 side by side; it can run two operating systems at the same time, and each operating system uses the other CPU at times (e.g. the DG CPU handles all disk activity, the 8086 handles keyboard). The MSDOS available for it was greatly hacked by DG, and (like the MBC550) video RAM and IO ports aren’t where you’d expect them. Both the DG10 and MBC500 series don’t have ROM at the the top of conventional memory, so you cannot test for a BIOS signature (in fact reading upper memory can hang the computer or do strange things to the video) although it is probably that the manufacturer’s ID word with be zero for both machines."
- "Data General DG One - totally different to the DG 10, a laptop (the first decent one, IMHO), with a 4MHz 80C88. Much more compatible with an IBM PC, but the serial ports are different (int 14 okay, but hardware access involves a totally different UART on the first DG One), and the CMOS time/clock behavior is different (cannot recall details, but a regular DOS would set the time correctly but not the date, I think). I can get hold of one to test."
- "Olivetti M20 series - pretty incompatible (M24 not as bad as M20); the Machine ID word is 0xFE00 for the M20. Note low byte is zero, normally FF for an IBM PC, FE for an XT, etc."
- "In general, if the ID byte at f000:fffe isn’t in the range 0xfa to ff then expect compatibility problems. The ID words for clones I have come across are:"
|??2D||very old Compaq PC|
|??9A||very old Compaq XT|
|0036||"Magnum" or "Bison" XT clone|
|CA00||"Excel" XT clone|
|0000||Data General DG10, or Sanyo MBC550|