About this page

Read this before annotating code. What the game is documented to do, with verification status against the binary. Statuses: open (documented, not found yet), traced (in the code, could not be exercised; say what was tried), confirmed (in the code, consistent with the emulator), live (observed directly), differs (the code does something else). "Absent" is not a status.

Sources, all read on 29 September 2026. Every web page was read through a fetch tool that summarises, so a quotation below is near-verbatim, not a transcription; work/research.md has the notes, source by source.

• The Commodore 64 manual, as text: <https://www.abandonwaredos.com/docawd.php?sf=ghostbustersmanual.txt&st=manual&sg=Ghostbusters&idg=3463> (it says LOAD "*",8,1 and a joystick in port one, so it is the C64's). The main source. It gives no prices.
• C64-Wiki, <https://www.c64-wiki.com/wiki/Ghostbusters>, and the German <https://www.c64-wiki.de/wiki/Ghostbusters>: credits, vehicles, cheats.
• Cobra1's C64 FAQ on GameFAQs, <https://gamefaqs.gamespot.com/c64/575568-ghostbusters/faqs/22229>: controls per screen, prices, fees. An Apple II guide filed under the C64 (.../faqs/58788) agrees on the prices.
• English Wikipedia, <https://en.wikipedia.org/wiki/Ghostbusters_(1984_video_game)>: credits and history.
• Zlin, "Ghostbusters: generiamo il nostro account number personale", ready64.org, 3 November 2008, <https://ready64.org/articoli/leggi/idart/66/ghostbusters-generiamo-il-nostro-account-number-personale>, and John L. Scarfone's gbaccount.py, <https://github.com/lagomorph/gbaccount>: the account number.
• Not reachable from this session: the Internet Archive's scan of the instructions (Ghostbusters_1984_Activision_524_Instructions), Lemon64, MobyGames, StrategyWiki's game page. No external screenshot could be saved (the network refuses downloads here), so reference/ holds the game's own screens only.
• The game's own screens, from the contributor's image in VICE and in the kit's simulator (orientation.md), and its stored text (the string sweep, facts.md).

Features

Beyond the documentation

Found in the code, not in the manual.

Open questions

• F1 and F3: the code accepts only these two keys to start ($6399); no player count is chosen anywhere (the title loop reads nothing else).
• POKE 22014,9 ("unlimited lives") lands in the screen at $5400, which the start-up clears and nothing reads (agent 2, seven states, 900 frames each): it does nothing in this image. POKE 38454,96 is settled above.
• Which words each speech phrase says: not settled from the code, and the simulator's samples were not listened to.

How to get from the contributor's own copy to the analysed state. Someone else must be able to follow this exactly.

The image

Ghostbusters_OneLoad64_J1.prg (64,750 bytes, SHA-256 6f74b24dc06ce9aec13bd35d677eef196aadd348ad9758d924ae18950acb5bda, MD5 a7504f10a17e5bbd15301b9934b47b20), the contributor's own copy, a single program file. Its load address is $0314 and it runs to $FFFF: 64,748 bytes, the whole of memory above the KERNAL's vectors.

It is not Activision's own disk. The name says it is from OneLoad64, a collection that turns C64 games into one file each, and the file behaves like one: there is no BASIC line and no SYS. The first two bytes loaded overwrite the IRQ vector at $0314 with $033C, so the first interrupt after the load has finished runs the program. What the conversion changed in the game is unknown: no original disk was available to compare with, and the stub at $C800 (below) is the only code found that is plainly not Activision's. No intro, trainer or credit to a converter appears on screen.

From power-on to play

1. Power-cycle the emulator (vice_machine_reset, mode: hard) and let it reach READY..
2. Do not autostart the file. VICE's autostart loads it through the drive, slowly, with interrupts running: as soon as $0314-$0315 are loaded, the next IRQ jumps to $033C before the code there has arrived, hits a BRK in the power-on pattern, and BASIC's warm start puts READY. back on the screen (seen three times, 29 September 2026; VICE's log says Autostart: Left ROM for $033C). The file is made for a loader that writes memory in one go, as a cartridge or a DMA loader does. work/inject.py does the same through the emulator: it stops the machine at READY., writes $0314-$CFFF and $E000-$FFFF with vice_memory_write, sets $01 to $34 to write $D000-$DFFF into the RAM under the I/O chips, puts $01 back to $37, checks all 64,748 bytes against the file, and resumes. The next raster IRQ enters $033C.
3. The title screen follows at once: the GHOSTBUSTERS logo, the no-ghost sign, the Activision logo and a bouncing-ball sing-along of the theme song ("PRESS F1 OR F3 TO START"). F1 starts the game.
4. A typed interview follows. Name: SPENGLER, RETURN. "DO YOU HAVE AN ACCOUNT?": N, RETURN. The bank advances $10,000. Vehicle selection: 2 (the 1963 hearse, $4,800), RETURN.
5. The equipment shop: three pages (keys 1-3), a forklift driven with the joystick in control port 1 picks an item up (fire), carries it right to the car and drops it (fire). Bought on page 2: three traps, one ghost bait, one ghost vacuum ($2,700). E ends shopping.
6. The city map appears, with CITY'S PK ENERGY counting up from 000 and $2500 in the account. That is play.

Snapshots in work/, each saved without ROMs:

Steady state

On the city map: $01 = $35 (RAM at $A000 and $E000, I/O at $D000); the hardware IRQ vector $FFFE = $8E76 and NMI $FFFA = $6425, both written by the start-up at $6000. The page at $0300, the KERNAL's vectors included, holds what $C800 copied there ($0314 reads $0A00), and nothing goes through it once the KERNAL is banked out. The video chip looks at bank 1 ($4000-$7FFF; $DD00 bits 0-1 set to %10 at $6033).

Compared byte for byte with entry.vsf, play-map.vsf differs in $4000-$5FFF (the video bank's screen and graphics, rebuilt), one byte at $6328, and scattered working storage at $E000-$F4E5. Everything else between $0314 and $FFFF is unchanged, so the program is not reloaded or unpacked while it runs: the image holds the whole game.

The loader, in a paragraph

There is none of Activision's in the file. The stub at $033C (in the cassette buffer) acknowledges the raster interrupt, blanks the screen, paints the border, the background and colour RAM black, resets the stack to $FB, copies the KERNAL's default vectors from ROM ($FD30, 20 bytes) back to $0314, waits 25 frames, calls the KERNAL's IOINIT ($FDA3), turns the screen back on and calls $C800. That routine masks every CIA interrupt, copies 256 bytes from $C830 to $0300, clears $0200-$02FF and jumps to $6000, never returning to the stub: it puts back pages $0200 and $0300, which the one-file load had to overwrite, as the conversion found them. $6000 is the game's cold start (SEI, stack to $FF, vectors at $FFFA/$FFFE, $01 = $35).

Every byte of the C64's 64 KB, one pixel each, 512 to a row. Lit pixels are code, graphics, sound, text, tables and variables; dim areas are screen and working memory.