IBM PC/AT

Boots DOSBox (em-dosbox / js-dos) to a DOS C:\> command prompt. Click the screen, then type at the prompt (try DIR, then MEM). Add ?debug, or click Debug, to inspect the LIVE x86 registers, read physical memory, and single-step the CPU. Pausing installs a dedicated frame loop that yields to the browser, so the debugger stays responsive; Step runs exactly one instruction (DOSBox's own CPU_Cycles=1 primitive).

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

Boots the IBM PC (Model 5150) straight to IBM Cassette BASIC ("The IBM Personal Computer Basic ... Ok"). Type BASIC directly (e.g. 10 PRINT"HELLO":GOTO 10, then RUN). Add ?debug, or open the debugger, to single-step the 8088 and set breakpoints. Click the screen first so it captures the keyboard.

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

Boots the IBM PC (Model 5150) straight to IBM Cassette BASIC ("The IBM Personal Computer Basic ... Ok"). Type BASIC directly (e.g. 10 PRINT"HELLO":GOTO 10, then RUN). Add ?debug, or open the debugger, to single-step the 8088 and set breakpoints. Click the screen first so it captures the keyboard.

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).

A full x86 PC in WebAssembly, booting a menu of real operating systems from self-hosted disk images: FreeDOS (A:\> prompt), Windows 3.0 / 3.1, Windows 95, Windows 98 and ReactOS to their desktops, plus a small Buildroot Linux. Windows 98 and ReactOS resume from a pre-booted state snapshot, so they come up already on the desktop; Windows 3.x and 95 cold-boot from disk (give 95 a minute). Click the screen, then use the keyboard and mouse. Add ?debug, or click Debug, to inspect the live x86 registers, read physical memory, and step the CPU. Step runs one v86 time-slice (see the notes: a JIT-in-WASM core has no clean one-instruction step).