Paused
Using the keyboard
At BASIC’s Ok prompt, type PRINT 2+3 and press Enter. You can paste several lines at once. Ctrl-Break interrupts a running BASIC program. Ctrl-Alt-Del sends the XT restart chord.
| Routine | CS:IP | Physical | Bytes | Instruction | Destination | BIOS note |
|---|
From the CPU specification
Previewed storage accesses
A private copy predicts the next boundary. Port I/O, TEST, and coprocessor connections stop the preview.
Physical 00000–FFFFF · enter hex or segment:offset · -- means no storage
Enter a physical address such as FE05B to match every segment alias, or F000:E05B to match that exact CS:IP.
Breakpoints
RAM write watchpoints
Watches stop after a write to RAM 00000–9FFFF, including unchanged values. Segment:offset entries select a physical RAM byte.
About this history
Oldest first. Captures conventional RAM writes to all configured watches, including unchanged stores and interrupt entry. The checkboxes enable stopping; disabled watches still record history. Live and Changes recording do not control capture. Removing a watch clears its history. Reset, power-on, restoration, and ROM replacement clear all history. Code links use the captured CS:IP but browse current storage. Reads, CGA RAM, ROM, and port I/O are excluded.
Before running
What to observe
Selecting a checkpoint only changes the guide. Run stops before its address, or after 2,000,000 boundaries. Breakpoints and RAM write watchpoints can stop it earlier; see Execution or Debugger for the reason. Reaching an address does not verify the setup. Step and Run remain in Execution.
Recorded changes
Recording · 0 / 500 events retained
CPU address or user action · before → after · newest first
About this log
Values are hex; flags use 0 and 1. Filters only change what is shown. Records every CPU boundary, even with this tab closed. Keeps the latest 500 events.
Pause recording to keep a capture while the CPU runs. Event numbers leave gaps for unrecorded steps. Clear log restarts numbering.
Memory lists actual RAM changes in write order, including CGA RAM at its first physical window (B8000); BC000 aliases name the same stored bytes. Unchanged stores, ROM and device writes are omitted. Reset, power-on, state restoration and successful media replacement clear the log.
No events recorded yet.
Load the three ROMs, then choose Quick boot to start a fresh session. For the full 640 KiB RAM test, choose Fresh power-on and Run. An empty drive starts ROM BASIC.
XT BIOS · 11/08/82 8 KiB
Empty
IBM BASIC · C1.10 32 KiB
Empty
IBM MDA/CGA character ROM 8 KiB
Empty
Verified files are remembered in this browser. Firmware guide ↗
Local checkpoint
No checkpoint saved.
Pause and save a snapshot to resume here next time. Saving replaces this browser’s XT checkpoint, including the mounted disk, screen, and pending input.