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GameBoy Recompiler — Accuracy Report

Generated: 2026-03-17
Recompiler version: gbrecomp at build/bin/gbrecomp
Test suites: Mooneye MTS 2024-09-26, Blargg GB Test ROMs

Summary

Suite Passed Total Pass Rate
Blargg 3 8 38%
Mooneye acceptance 25 62 40%
Total 28 70 40%

Blargg CPU / Timing Tests

These ROMs output ASCII text via the serial port. "Passed" in the output = pass.

Test Result Serial output
01-special ✅ PASS 01-special · · · Passed
cpu_instrs ✅ PASS cpu_instrs · · 01:ok 02:ok 03:ok 04:ok 05:ok 06:ok 07:ok 08:ok 09:ok 1
instr_timing ✅ PASS instr_timing · · · Passed
halt_bug ❌ FAIL
interrupt_time ❌ FAIL
mem_timing-1 ❌ FAIL mem_timing · · 01:01 02:01 03:01 · · Failed 3 tests.
mem_timing-2 ❌ FAIL
oam_bug ❌ FAIL

Mooneye Acceptance Tests

Mooneye tests signal pass by writing the Fibonacci sequence 03 05 08 0D 15 22 to the serial port. Tests marked GS target DMG/SGB hardware specifically.

bits

Test Result Notes
mem_oam ✅ PASS
reg_f ✅ PASS
unused_hwio-GS ❌ FAIL

instructions

Test Result Notes
daa ✅ PASS

interrupts

Test Result Notes
ie_push ❌ FAIL

OAM DMA

Test Result Notes
basic ✅ PASS
oam_dma_restart ❌ FAIL
oam_dma_start ❌ FAIL
oam_dma_timing ❌ FAIL
reg_read ❌ FAIL
sources-GS ❌ FAIL

PPU

Test Result Notes
stat_irq_blocking ✅ PASS
hblank_ly_scx_timing-GS ❌ FAIL
intr_1_2_timing-GS ❌ FAIL
intr_2_0_timing ❌ FAIL
intr_2_mode0_timing ❌ FAIL
intr_2_mode0_timing_sprites ❌ FAIL
intr_2_mode3_timing ❌ FAIL
intr_2_oam_ok_timing ❌ FAIL
lcdon_timing-GS ❌ FAIL
lcdon_write_timing-GS ❌ FAIL
stat_lyc_onoff ❌ FAIL
vblank_stat_intr-GS ❌ FAIL

Timer

Test Result Notes
div_write ✅ PASS
tim00 ✅ PASS
tim00_div_trigger ✅ PASS
tim01 ✅ PASS
tim01_div_trigger ✅ PASS
tim10 ✅ PASS
tim10_div_trigger ✅ PASS
tim11 ✅ PASS
tim11_div_trigger ✅ PASS
rapid_toggle ❌ FAIL
tima_reload ❌ FAIL
tima_write_reloading ❌ FAIL
tma_write_reloading ❌ FAIL

Misc timing

Test Result Notes
di_timing-GS ✅ PASS
div_timing ✅ PASS
ei_sequence ✅ PASS
ei_timing ✅ PASS
halt_ime0_ei ✅ PASS
halt_ime0_nointr_timing ✅ PASS
halt_ime1_timing ✅ PASS
halt_ime1_timing2-GS ✅ PASS
intr_timing ✅ PASS
rapid_di_ei ✅ PASS
reti_intr_timing ✅ PASS
add_sp_e_timing ❌ FAIL
call_cc_timing ❌ FAIL
call_cc_timing2 ❌ FAIL
call_timing ❌ FAIL
call_timing2 ❌ FAIL
if_ie_registers ❌ FAIL
jp_cc_timing ❌ FAIL
jp_timing ❌ FAIL
ld_hl_sp_e_timing ❌ FAIL
pop_timing ❌ FAIL
push_timing ❌ FAIL
ret_cc_timing ❌ FAIL
ret_timing ❌ FAIL
reti_timing ❌ FAIL
rst_timing ❌ FAIL

Known Limitations

  • Cycle-exact timing: The static recompiler batches instructions between sync points; cycle-exact Mooneye timing tests (call/ret/jp/push/pop timing, TIMA edge cases) may fail even when the interpreter is otherwise correct.
  • Boot ROM: Tests that check post-boot register state (boot_regs-*, boot_div-*, boot_hwio-*) are skipped — the recompiler does not emulate the boot ROM.
  • CGB-only tests: Any test suffixed -C (CGB-only mode) is expected to fail on this DMG-targeted recompiler.
  • mem_timing / halt_bug / oam_bug / interrupt_time: These Blargg tests exercise edge cases around memory access timing, the HALT bug, OAM corruption, and interrupt timing that the current runtime does not fully model.
  • PPU sub-mode timing: Most Mooneye PPU tests check interrupt timing at exact T-cycle boundaries; the PPU emulation does not currently reach that granularity.