Banjo-Kazooie/Stop N Swop

This is a sub-page of Banjo-Kazooie.

During the development of Banjo-Kazooie, Rare had discovered a method of cold swapping that would allow the data from one cartridge to survive a power cycle and be read by another. Intending to use this transfer method to unlock bonuses across games, seven secret items were hidden away in Banjo-Kazooie, accessible only by connecting to a future title through cartridge swapping.

Dubbing this connection Stop 'N' Swop, the developer had grand plans to include at least six of their future Nintendo 64 titles in the proposed trading sequence, including Donkey Kong 64, which had been developed with this elaborate connection in mind.

In October 1999, Nintendo raised concerns regarding the viability of Stop 'N' Swop and its method of data transfer via cartridge swapping, and urged Rare to cancel the enigmatic feature outright. Since then, the infamous Stop 'N' Swop has become Rare's most widely-discussed secret, with the community coming together to discover the intriguing remnants of the lost feature, in an attempt to piece together the full mystery...

What's Still In The Game

If a player defeats Gruntilda and collects all 100 Jiggies, they will witness a bonus ending in which Mumbo-Jumbo shows Banjo and Kazooie revisiting areas they had previously explored to obtain secret items. These items included a Pink Egg in the sunken "Sharkfood Island" in Treasure Trove Cove, a Blue Egg behind a sealed door in Gobi's Valley, and an Ice Key behind a glazed alcove in Freezeezy Peak.

Players were informed by Mumbo that they would need to wait until the release of Banjo-Tooie before they would be able to collect the items, and use them in that game. While Banjo-Tooie would release just two years later in 2000, its link had been effectively severed after Nintendo's edict for Stop 'N' Swop's removal in 1999, making the connection impossible.

Luckily, the items shown as well as four additional Mystery Eggs can still be unlocked and collected in Banjo-Kazoie by using secret contingency codes: If a player visits the Sandcastle in Treasure Trove Cove after obtaining its Jiggy, and types in the word "CHEAT", they will hear a cow moo after each successive letter and be able to type in the following cheats for each item:

Code	Result
NOW YOU CAN SEE A NICE ICE KEY WHICH YOU CAN HAVE FOR FREE	Inside Wozza's Cave in Freezeezy Peak, the thick sheet of ice that prevented players from continuing through the alcove will be smashed open, allowing players to venture towards the Ice Key atop a plinth. Curiously, this was one of the first Stop 'N' Swop items to be obtained, due to the use of the "Press L to Levitate" GameShark code.
OUT OF THE SEA IT RISES TO REVEAL MORE SECRET PRIZES	Just outside the Sandcastle, a submerged island with a signpost above sea level reading "Sharkfood Island" will emerge, towering above the beach, revealing an entrance at its base. Swimming out to sea and venturing inside the formerly submerged island, players will find a large spire with alcoves spiralling upwards, allowing progress. At the very top sits the Mystery Pink Egg.
A DESERT DOOR OPENS WIDE ANCIENT SECRETS WAIT INSIDE	In Gobi's Valley, players can ride a magic carpet to arrive at an alcove carved into the cliff side where they had obtained a hollow honeycomb from Gobi. The impenetrable sealed door which had previously barred progress will now be missing, allowing players into a secret tomb. The chamber harbours a golden sarcophagus with a switch placed in front. Activating this switch causes the sarcophagus to open, revealing the Mystery Blue Egg.
DONT YOU GO AND TELL HER ABOUT THE SECRET IN HER CELLAR	Venturing into Mad Monster Mansion, the entrance to the Cellar can be found at the rear of the estate. Finding rows of wine casks labelled "1881", players will find that the barrel that had previously had a pair of bars welded to its front has had its lid removed entirely, revealing a secret passage. Travelling down this tunnel will lead to a small room harbouring the Mystery Cyan Egg.
AMIDST THE HAUNTED GLOOM A SECRET IN THE BATHROOM	Also featured in Mad Monster Mansion, the location of this mystery egg can be found in the bathroom on the second floor. If players can clamber onto the rooftop and smash through the window, they'll reintroduce themselves to Loggo the Toilet, finding the Mystery Green Egg on his tank. Curiously, this Mystery item is the first to simply "appear" in a previously visited area.
THIS SECRET YOULL BE GRABBIN IN THE CAPTAINS CABIN	In Rusty Bucket Bay, players will need to board the eponymous ship and make their way across to the starboard side near the Whistle Puzzle, finding a pair of windows near a rowboat. Busting up the port windows with a Rat-a-tat Rap will allow players inside the Captain's Cabin, where they'll find the Mystery Red Egg sitting atop the Captain's bed.
NOW BANJO WILL BE ABLE TO SEE IT ON NABNUTS TABLE	In Click Clock Wood, players will need to enter the Winter season door, and make their way up the tree towards Nabnut's House. As the squirrel's door is locked, players will need to invite themselves inside with a Rat-a-tat Rap on his window. Inside, next to a hibernating Nabnut and Nibblenut, players will find the Mystery Yellow Egg on the table.

As soon as the player collects one of these previously hidden items, a new menu called "Stop 'n' Swop" will appear when scrolling past Click Clock Wood in the Game Totals option, showcasing all of the secret items obtained up to that point. None of the Mystery Eggs or the Ice Key have any effect in-game; they were intended to be collected in Banjo-Kazooie, but then utilized in future titles by transferring them via cartridge swapping. If Stop 'N' Swop had been implemented in Banjo-Tooie, or Donkey Kong 64 as intended, players would simply need to turn off Banjo-Kazooie, remove the cartridge from the Nintendo 64 console, and replace it with another relevant cartridge and power on. The second cartridge which was prepared for the feature, would rely on the fact that the Nintendo 64 console retained Rambus memory reliably for around 10 seconds, hence the name "Stop 'N' Swop".

While Rare had quietly abandoned the feature, including the secret items in Banjo-Tooie from the start, the truth of Stop 'N' Swop was subject to many rumors and speculation for decades. It wasn't until 2020 when Paul Machacek, the Rare engineer behind the feature, revealed the full story, first on Rare Gamer and later on Twitter. Following the release of Banjo-Kazooie in 1998, Rare envisioned Donkey Kong 64 as the next title that would utilize the secret items, specifically the Ice Key. Development of DK64 continued through to 1999, with its planned release in November of that year. However, in October, Nintendo raised their concerns with how the feature was to use cartridge swapping to transfer data between titles. Due to their concerns that latch-up conditions could be experienced leading to hardware malfunction, and the possibility that future models of the Nintendo 64 could reduce the window for the Rambus memory, they ordered Stop 'N' Swop to be removed entirely.

Without any recourse, Rare removed the relevant Stop 'N' Swop programming from Donkey Kong 64, leaving only remnants of its existence in the released title, like the data relating to the Ice Key, Ice Door, and their plans to continue the process with a Golden Statue.

(Source: Paul Machacek)

While Banjo-Kazooie still contains the Mystery Eggs and Ice Key, and is capable of "sending" the data to another Rare game, no other Nintendo 64 title is capable of accepting and utilizing said data. The codes and items in Banjo-Kazooie are effectively permanent: new games started after these codes are input will begin with the locations unlocked, and new games started after the items are collected will still have them collected. Deleting any or all of the three files will not reset the Stop 'N' Swop items or locations; the only way to erase these items is to use GameShark code 81283400 0000.

Rare reintroduced the concept in the Xbox Live Arcade release of Banjo-Kazooie: although these codes are no longer permanent, getting wiped after exiting the save, having Banjo-Tooie and/or Banjo-Kazooie: Nuts & Bolts save data on the console unveils all the locations permanently. Then, collecting the items both adds them to the player's inventory in Banjo-Tooie (which makes the breakable N64 carts drop different items for a "Stop 'n' Swop II") and unlocks rare parts in Nuts & Bolts.

(Source: Rare Gamer)

The Mechanism

The original Stop 'N' Swop mechanism is left unused in Banjo-Kazooie, but is still fully functional.

On boot, the game scans all of main memory for a special 128-byte payload left behind by another game.

This payload starts with the magic number 0xC908C52F, contains data in the next 112 bytes (to transfer items between games), has 4 bytes of padding, and ends with two 4-byte checksums. If the magic number is present and the checksums are valid, the contents are transferred to an in-game word array, and then read by the game to make the relevant Stop 'N' Swop items accessible.

Receiving data from other games
The incoming payload should contain some or all of the values 0x108 through 0x10E inclusive:

Value	Purpose
0x108	Makes the Yellow Egg appear (Click Clock Wood, Winter: Nabnut's Table)
0x109	Makes the Red Egg appear (Rusty Bucket Bay: Captain's Cabin)
0x10A	Makes the Green Egg appear (Mad Monster Mansion: Loggo the Toilet)
0x10B	Grants access to the Blue Egg (Gobi's Valley: Secret Chamber)
0x10C	Grants access to the Pink Egg (Treasure Trove Cove: Sharkfood Island)
0x10D	Grants access to the Cyan Egg (Mad Monster Mansion: Cellar)
0x10E	Grants access to the Ice Key (Freezeezy Peak: Wozza's Cave)

Here's a payload that will make all seven Stop 'N' Swop items accessible if placed in RAM before the game boots, and at any 128-byte boundary past the first ~1MB of memory (e.g. at 0x80200000)

To use with latest Project64:

1. Enable the debugger (Settings > Options > Advanced > Enable debugger)
2. Open Banjo-Kazooie, and hit F2 to freeze the game as early as possible
3. Open the memory viewer (Debugger > View Memory)
4. Paste the payload at the desired address, e.g. 0x80200000
5. Close the viewer and hit F2 to resume the game

Make all Stop 'n' Swop items accessible
C908C52F 00000108 00000109 0000010A 0000010B 0000010C 0000010D 0000010E 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 638AE93A 22A1C3FD

Sending data to other games
The game also writes outgoing payloads into memory, meant to be sent to and read by another game. These are the values of one or more of the Stop 'n' Swop items you've collected in the game, represented by the values 0x100 to 0x106 inclusive. It also writes the value 0x1, but its purpose is unclear.

Value	Purpose
0x1	(unknown)
0x100	Sends the Yellow Egg
0x101	Sends the Red Egg
0x102	Sends the Green Egg
0x103	Sends the Blue Egg
0x104	Sends the Pink Egg
0x105	Sends the Cyan Egg
0x106	Sends the Ice Key

Here's the payload meant to send all seven items to other Rare games:

Send all Stop 'n' Swop items to other games
C908C52F 00000001 00000100 00000101 00000102 00000103 00000104 00000105 00000106 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 55E7E71F 32815BC5

Interestingly, the magic number 0xC908C52F, when shifted right by 2, gives the ASCII string "2B1K". The orderly presence of the letters B and K suggests that this is not a coincidence, but the meaning of the numbers 2 and 1 are unclear.

(Source: Wedarobi)