What are the computer requirement for real time processing?

Any computer is capable of processing in realtime.

If you mean Realtime Mode, a DOS operating system mode and processor mode, then it requires any version of DOS 1.0 or later, and an x86 based computer (with coprocessor in the case of an 8086, 286, and 386) with a processor capable of addressing at least 8 bits of memory space (256 bytes), preferably a 16-bit address space (64 KB) and up to 640 KB address space.

In order to utilize more than 640 KB of memory, you will need to operate in Protected Mode, which requires a 286 or greater, preferably a 386 or better. The 486 was the first processor which made extensive standard use of Protected Mode in DOS, to utilize for games and operating systems (such as Windows 3 and Windows 95)