What if the IBM PC used ARM instead of x86? A fantasy ARM based PC, running a native ARM port of DOS+Apps with a Rosetta-like X86 JIT translator for full PC compatibility.
Click a diskette to put it in drive A:, or drag it there. Drop a 1.44 MB .img on the drive to use it as a diskette, or drop ordinary files to copy them onto the diskette in the drive.
Drive C: remembers your changes in this browser until C: gets a new version.
Drive D: is yours to keep, in this browser, through every update.
Click a file to download it. Drop files from your computer on this list or on the drive to copy them in; long names are cut down to DOS’s 8.3. The diskette pops out and back in while it is written, so DOS notices the change. C: and D: accept files only while the machine is switched off.
COPY README.TXT PRN.It's 1988, and IBM has put Acorn's new RISC chip in the AT instead of an Intel 286. Microsoft ported DOS 4.00 to it over a long weekend. The ports, the BIOS data area, the text buffer at B8000 and every INT 21h function are right where a PC keeps them; only the processor is different.
Everything on that screen is drawn by real ARM machine code. The BIOS that counts memory, the boot sector, the DOS kernel and COMMAND.COM are all compiled for an ARM926 and executed instruction by instruction by an emulator running in this tab. Open the inspector on the right to watch the registers change, pause the processor, and step through its code yourself.