Bangkok Knights - Revision history

Enigma at 00:17, 4 October 2026

2026-10-04T00:17:52Z

← Older revision		Revision as of 00:17, 4 October 2026
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	[[File:bangkok_knights_rene_s1.g64]]		[[File:bangkok_knights_rene_s1.g64]]

			== Why Bangkok Knights does not load on a 1541-II ==

			Bangkok Knights loads on a 1541 but hangs on a 1541-II. The cause is not
			the [[Para Protect]] track-40 read. Every ROM routine its drive-side reader
			calls (<code>$F6D0</code>, <code>$F8E0</code>, <code>$F24B</code>,
			<code>$F969</code>, the job loop at <code>$F31B</code>) is byte-identical in
			both drive ROMs: 1541 325302-01 + 901229-05, and 1541-II 251968-03. The
			failure also happens earlier, about 5 seconds into loading, while the head
			is still on track 18.

			=== The faulty loop ===

			The cause is a drive-side loop in the game's boot chain. It copies drive ROM
			from <code>$C000</code> over code at <code>$0700</code> that has already run,
			presumably to erase it:

			<pre>
			$0727 A2 29 LDX #$29
			$0729 BD 00 C0 LDA $C000,X
			$072C 9D 00 07 STA $0700,X
			$072F CA DEX
			$0730 10 F7 BPL $0729
			</pre>

			The counter starts one byte too high. The first store
			(<code>X = $29</code>) writes ROM byte <code>$C029</code> over the loop's
			own opcode at <code>$0729</code>, so the next pass executes whatever that
			ROM byte is.

			=== On a 1541 ===

			The 1541 ROM area <code>$C000</code>–<code>$C0FF</code> is filler, so
			<code>$C029</code> = <code>$AA</code>, which is <code>TAX</code>:

			# <code>$0729</code> now reads <code>AA 00 C0</code>. The next pass executes
			<code>TAX</code>, so X = <code>$AA</code>.
			# <code>$072A</code> is <code>$00</code>, a <code>BRK</code>. The drive's IRQ
			handler at <code>$FE67</code> doesn't check for BRK and returns with
			<code>RTI</code> to <code>$072C</code>.
			# <code>STA $0700,X</code> writes to <code>$07AA</code>. Then
			<code>DEX</code> gives <code>$A9</code>, which is negative, so
			<code>BPL</code> falls through.

			The loop ends after copying a single byte, and loading carries on as if
			nothing happened.

			=== On a 1541-II ===

			The 1541-II ROM holds its copyright text in that area:
			<code>"…COPYRIGHT (C)1982,1985,1987 COMMODORE ELECTRONICS…"</code>. So
			<code>$C029</code> = <code>$4C</code> (the letter "L"), which is
			<code>JMP</code>:

			# <code>$0729</code> now reads <code>4C 00 C0</code>, which is
			<code>JMP $C000</code>.
			# The drive executes the copyright text as code and ends up at
			<code>$C05F</code>. That is inside a helper routine that exists only in
			the 1541-II ROM (<code>$C04E</code>, called from the format code at
			<code>$FCAE</code>).
			# The helper waits for byte-ready at <code>$C066</code>, which never comes,
			so the drive hangs there.
			# The C64 waits forever for the drive.

			=== Comparison with After Burner ===

			After Burner uses the same buffer-2 loader and contains the same loop:

			<pre>
			$072E A2 2F LDX #$2F
			$0730 BD 00 C0 LDA $C000,X
			$0733 9D 00 07 STA $0700,X
			$0736 CA DEX
			$0737 10 F7 BPL $0730
			</pre>

			Here the copy covers <code>$0700</code>–<code>$072F</code> and stops one
			byte short of the loop itself, so After Burner works on both drives. In
			Bangkok Knights the counter is one too high for where the loop sits. This
			looks like an off-by-one bug that the 1541's <code>$AA</code> filler
			happened to hide, not a deliberate 1541-II check.

			=== Minimal patch that makes the game work on 1541-II ===

			The loop is stored unencrypted on the disk in '''track 18, sector 18'''.
			The drive loads this sector to <code>$0700</code> with an ordinary DOS READ
			job, but it has two quirks:

			* Its data block ID is <code>$12</code> instead of <code>$07</code>.
			* Its data checksum (<code>$F2</code>) is reused afterwards as a decryption key (<code>LDA $3A / STA $C1</code> at <code>$0705</code>), so the sector's checksum must not change.

			A two-byte patch fixes the problem and leaves the checksum unchanged:

			{\| class="wikitable"
			! Sector offset !! Address !! Old !! New !! Effect
			\|-
			\| <code>$2A</code> \|\| <code>$072A</code> \|\| <code>$00</code> \|\| <code>$C9</code> \|\| <code>LDA $C000,X</code> becomes <code>LDA $C0C9,X</code>. With X = <code>$29</code> it reads <code>$C0F2</code>, which is filler <code>$AA</code> in both ROMs.
			\|-
			\| <code>$AA</code> \|\| <code>$07AA</code> \|\| <code>$00</code> \|\| <code>$C9</code> \|\| Compensates the checksum (<code>$00 XOR $C9</code> twice, so the XOR stays <code>$F2</code>). The loop overwrites this byte with <code>$AA</code> before anything reads it.
			\|}

Enigma at 07:45, 23 December 2022

2022-12-23T07:45:30Z

← Older revision		Revision as of 07:45, 23 December 2022
Line 72:		Line 72:
	\| Title \|\| Bangkok Knights		\| Title \|\| Bangkok Knights
	\|-		\|-
	\| Publisher and/or Developer \|\| Boeder, System 3 Software Ltd., Activision Ltd.		\| Publisher and/or Developer \|\| Boeder/bitstar Games, System 3 Software Ltd., Activision Ltd.
	\|-		\|-
	\| Year \|\| 03/1992		\| Year \|\| 03/1992

Enigma at 07:41, 23 December 2022

2022-12-23T07:41:48Z

← Older revision		Revision as of 07:41, 23 December 2022
Line 64:		Line 64:

	[[File:BangkokKnights_Rakki_s1.g64]]		[[File:BangkokKnights_Rakki_s1.g64]]

			== Source 2 == <!--T:2-->
			{\| class="wikitable"
			\|-
			! Property !! Data
			\|-
			\| Title \|\| Bangkok Knights
			\|-
			\| Publisher and/or Developer \|\| Boeder, System 3 Software Ltd., Activision Ltd.
			\|-
			\| Year \|\| 03/1992
			\|-
			\| Disk(s) \|\| 1
			\|-
			\| Number of Index Holes \|\| 1
			\|-
			\| Media Type \|\| 5.25 DSDD
			\|-
			\| Retail, Budget or Compilation (with name) \|\| Budget
			\|-
			\| Country of Release \|\| DE
			\|-
			\| Language(s) \|\| English
			\|-
			\| Platform \|\| C64
			\|-
			\| NTSC or PAL \|\| PAL
			\|-
			\| Protection \|\| None
			\|-
			\| Working? \|\| Yes, Stream has an error on side 1 track 31 sector 11, but could be repaired in G64.
			\|-
			\| Archived \|\| 18 Dec 2022 Rene
			\|-
			\| Verified by \|\| enigma
			\|}
			<gallery>
			File:bangkok_knights_rene_a_dos_r1.png\|Side 0
			File:bangkok_knights_rene_b_dos_r1.png\|Side 1
			</gallery>
			<gallery>
			File:bangkok_knights_bitstar_rene.jpg\|Disk
			</gallery>
			===== Streams =====
			[[File:Streams_bangkok_knights_rene.zip]]
			===== G64 =====
			[[File:bangkok_knights_rene_s0.g64]]

			[[File:bangkok_knights_rene_s1.g64]]

Enigma at 02:19, 1 September 2022

2022-09-01T02:19:05Z

← Older revision		Revision as of 02:19, 1 September 2022
Line 1:		Line 1:
	[[Category:C64 Game]]		[[Category:C64 Game]]

	[https://www.mobygames.com/game/c64/bangkok-knights mobygames link]		[https://www.mobygames.com/game/c64/bangkok-knights mobygames link]

	== Source 1 == <!--T:2-->		== Source 1 == <!--T:2-->

	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-
Line 39:		Line 37:
	\| Verified by \|\| enigma		\| Verified by \|\| enigma
	\|}		\|}

	<gallery>		<gallery>
	File:BangkokKnights_Rakki_a_dos_r1.png\|Side 0		File:BangkokKnights_Rakki_a_dos_r1.png\|Side 0
Line 60:		Line 57:
	File:BangkokKnights_Rakki_game.png\|Game		File:BangkokKnights_Rakki_game.png\|Game
	</gallery>		</gallery>

	Purchased from: ebay.co.uk / gurl_gamer		Purchased from: ebay.co.uk / gurl_gamer

	===== Streams =====		===== Streams =====

	[[File:Streams_BangkokKnights_Rakki.zip]]		[[File:Streams_BangkokKnights_Rakki.zip]]

	===== G64 =====		===== G64 =====

	[[File:BangkokKnights_Rakki_s0.g64]]		[[File:BangkokKnights_Rakki_s0.g64]]

	[[File:BangkokKnights_Rakki_s1.g64]]		[[File:BangkokKnights_Rakki_s1.g64]]

Enigma at 11:28, 12 June 2020

2020-06-12T11:28:59Z

← Older revision		Revision as of 11:28, 12 June 2020
Line 33:		Line 33:
	\| Protection \|\| [[Para Protect]]		\| Protection \|\| [[Para Protect]]
	\|-		\|-
	\| Working? \|\| No		\| Working? \|\| Yes (requires 1541, protection check does not work on 1541-II)
	\|-		\|-
	\| Archived \|\| 8 Jul 2014 Rakki		\| Archived \|\| 8 Jul 2014 Rakki
Line 53:		Line 53:
	File:Bangkok Knights Disk Label.JPG\|Disk Label		File:Bangkok Knights Disk Label.JPG\|Disk Label
	File:Bangkok Knights Copyright Year.JPG\|Copyright		File:Bangkok Knights Copyright Year.JPG\|Copyright
			</gallery>
			<gallery>
			File:BangkokKnights_Rakki_loader.png\|Loader
			File:BangkokKnights_Rakki_title.png\|Title
			File:BangkokKnights_Rakki_menu.png\|Menu
			File:BangkokKnights_Rakki_game.png\|Game
	</gallery>		</gallery>

Enigma at 18:51, 11 June 2020

2020-06-11T18:51:41Z

← Older revision		Revision as of 18:51, 11 June 2020
Line 33:		Line 33:
	\| Protection \|\| [[Para Protect]]		\| Protection \|\| [[Para Protect]]
	\|-		\|-
	\| Working? \|\| ~~Yes~~		\| Working? \|\| No
	\|-		\|-
	\| Archived \|\| 8 Jul 2014 Rakki		\| Archived \|\| 8 Jul 2014 Rakki

Enigma: Created page with "Category:C64 Game [https://www.mobygames.com/game/c64/bangkok-knights mobygames link] == Source 1 == {| class="wikitable" |- ! Property !! Data |- | Title ||..."

2020-06-11T18:51:29Z

Created page with "Category:C64 Game [https://www.mobygames.com/game/c64/bangkok-knights mobygames link] == Source 1 ==  {| class="wikitable" |- ! Property !! Data |- | Title ||..."

New page

[[Category:C64 Game]]

[https://www.mobygames.com/game/c64/bangkok-knights mobygames link]

== Source 1 == 

{| class="wikitable"
|-
! Property !! Data
|-
| Title || Bangkok Knights
|-
| Publisher and/or Developer || System 3 Software Ltd., Activision Ltd.
|-
| Year || 1987
|-
| Disk(s) || 1
|-
| Number of Index Holes || 1
|-
| Media Type || 5.25 DSDD
|-
| Retail, Budget or Compilation (with name) || Retail
|-
| Country of Release || UK
|-
| Language(s) || English
|-
| Platform || C64
|-
| NTSC or PAL || PAL
|-
| Protection || [[Para Protect]]
|-
| Working? || Yes
|-
| Archived || 8 Jul 2014 Rakki
|-
| Verified by || enigma
|}

<gallery>
File:BangkokKnights_Rakki_a_dos_r1.png|Side 0
File:BangkokKnights_Rakki_b_dos_r1.png|Side 1
</gallery>
<gallery>
File:Bangkok Knights Front.JPG|Box Front
File:Bangkok Knights Front (No case).JPG|Box Front (no case)
File:Bangkok Knights Back.JPG|Box Back
File:Bangkok Knights Back (no case).JPG|Box Back (no case)
File:Bangkok Knights All.JPG|Box Content
File:Bangkok Knights Disk.JPG|Disk
File:Bangkok Knights Disk Label.JPG|Disk Label
File:Bangkok Knights Copyright Year.JPG|Copyright
</gallery>

Purchased from: ebay.co.uk / gurl_gamer

===== Streams =====

[[File:Streams_BangkokKnights_Rakki.zip]]

===== G64 =====

[[File:BangkokKnights_Rakki_s0.g64]]

[[File:BangkokKnights_Rakki_s1.g64]]