CPU Profiler

The profiler plots a whole frame of execution against the raster, reading back one full frame from the CPU history buffer. Each row is a scanline; the horizontal axis is time across that line. Every instruction from the history is drawn at the point in the frame it ran, so you can see which code runs on which raster line and how long it takes. It is the assembly equivalent of racing the beam.

Note: this can only be viewed while a debug session is active.

How to open

Open the command palette and run BitMagic: Open The CPU Profiler View. See VSCode’s command documentation to customise how you access it.

Colouring rules

Pixels are coloured by a list of rules, each a predicate (a C# expression over the instruction) plus a colour. Rules are tried top to bottom; the first whose predicate matches wins. Until you add a rule, every pixel is coloured by address, the same as the PC built-in below.

Add a rule with Add, remove one with the bin icon next to it, and drag a rule by its handle to reorder the list. Click Update to apply your changes and redraw; Fetch CPU Profile just redraws with whatever rules are already applied.

Each rule has:

• a predicate: a C# expression using any of PC, OpCode, RomBank, RamBank, A, X, Y, Params, Flags, SP, CpuY, Clock;
• a colour, one of:
  • Built In: PC (colour by address) or Op Code (colour by opcode);
  • Colour: picked from a colour swatch, stored as hex, e.g. #ff8800;
  • Custom RGB: explicit R, G and B, each itself a C# expression over the same fields.

For example, a rule of OpCode == 0xea with a bright red Colour shows exactly where nops are being executed across the frame.