Update readme

Author: jeremycole

README.md

@@ -14,6 +14,15 @@ I initially started this as an exercise in parsing some opcodes, as I was learni
 
 The CPU is nearly fully implemented. SRAM, Flash, and EEPROM memories are supported. Most opcodes work. Support for loading the flash (or any memory) from Intel hex is supported, so it's easy to load existing code. Basic RSpec tests are implemented for opcodes and some other things. Most peripherals are not implemented. Contributions (or insults) are welcome.
 
-Currently, many simple programs (such as blink) will run out of the box, although the CPU as emulated is exceedingly slow. It runs at ~140 kHz on a MacBook Pro with 2.8 GHz Intel Core i7 using Ruby 2.6.3.
+## Performance
+
+A simple benchmark can be run with the following command (note that Sorbet runtime type checking is enabled by default, so for performance testing it should be disabled with `SORBET_RUNTIME_DEFAULT_CHECKED_LEVEL=never`, the default is `always`):
+
+```bash
+SORBET_RUNTIME_DEFAULT_CHECKED_LEVEL=never \
+  bundle exec bin/avruby_shell -I test/blink/blink.hex -b 60
+```
+
+Currently, many simple programs (such as `blink`) will run out of the box, although the CPU as emulated is exceedingly slow. It runs at ~100 kHz on a MacBook Pro with 2.8 GHz Intel Core i7 using Ruby 3.3.5. Performance is not a goal, so this will vary somewhat over time with new features and refactors.
 
 # It's fun.