Common Emulator Development Issues - Revision history

MSaarna at 00:13, 4 June 2026

2026-06-04T00:13:29Z

MSaarna at 00:11, 4 June 2026

2026-06-04T00:11:22Z

MSaarna at 19:14, 24 February 2025

2025-02-24T19:14:24Z

MSaarna at 12:09, 9 May 2024

2024-05-09T12:09:58Z

MSaarna at 01:34, 21 January 2024

2024-01-21T01:34:54Z

MSaarna at 01:23, 21 January 2024

2024-01-21T01:23:33Z

MSaarna at 01:12, 21 January 2024

2024-01-21T01:12:01Z

MSaarna at 01:07, 21 January 2024

2024-01-21T01:07:42Z

Trebor: /* ROMs That May Be Reported As Bugs, But Aren't */

2023-06-03T00:44:46Z

‎ROMs That May Be Reported As Bugs, But Aren't

Trebor: /* ROMs That May Be Reported As Bugs, But Aren't */

2023-06-02T01:08:50Z

‎ROMs That May Be Reported As Bugs, But Aren't

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 * Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.
 * BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.
-* Pole Position II. If the track selection by joystick only allows selection between tracks 2 and 4, two emulation issues are the cause. 1. The first frame isn't starting in VBLANK -or- DMA is inaccurate. 2. The emulation host controls are only being populated in SWCHA once per frame. (The gory details - the PPII track selection routine reads SWCHA twice and assumes the same result for both. If that assumption is false, any move left will be undone when you stop moving left. On real hardware this isn't a likely event. On emulation that splits the two reads across frames, and only updates SWCHA once per frame, it's a guaranteed circumstance.)
+* Pole Position II. If the track selection by joystick only allows selection between tracks 2 and 4, two emulation issues are the cause. 1. The first frame isn't starting in VBLANK -or- DMA is inaccurate. 2. The emulation host controls are only being populated in SWCHA once per frame. (The gory details - the PPII track selection routine reads SWCHA twice and assumes the same result for both. If that assumption is false, any move left will be undone when you stop moving left. On real hardware this isn't a likely event. On emulation with timing that splits the two SWCHA reads across frames, and only updates SWCHA contents once per frame, it's a guaranteed circumstance.)
 * Klax. If the game starts up with black screen. you might need to change where the emulator starts in the screen, similar to Pole Position II. The Klax proto has a race condition, and has hit-or-miss startup on (some) real consoles too.
 * Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.

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 * Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.
 * BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.
-* Pole Position II. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.
+* Pole Position II. If the track selection by joystick only allows selection between tracks 2 and 4, two emulation issues are the cause. 1. The first frame isn't starting in VBLANK -or- DMA is inaccurate. 2. The emulation host controls are only being populated in SWCHA once per frame. (The gory details - the PPII track selection routine reads SWCHA twice and assumes the same result for both. If that assumption is false, any move left will be undone when you stop moving left. On real hardware this isn't a likely event. On emulation that splits the two reads across frames, and only updates SWCHA once per frame, it's a guaranteed circumstance.)
 * Klax. If the game starts up with black screen. you might need to change where the emulator starts in the screen, similar to Pole Position II. The Klax proto has a race condition, and has hit-or-miss startup on (some) real consoles too.
 * Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.

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 * Xenophobe. If the bottom row of the titlescreen graphic is the incorrect color, it means that DMA cycle penalties or timing aren't accurate.
 * Xenophobe. If all of the main action screen glitches periodically, it means that DMA cycle penalties or timing aren't accurate.
-* Ninja Golf. If the player number selection screen has squished graphics (displaying 160A graphics at 160B) then you need to account for non-zero DLL terminators. Maria ignores bits 7 and 5, so your terminator check should be for "!(value & 0x5F)".
+* Ninja Golf. If the player number selection screen has squished graphics (displaying 160A graphics at 160B) then you need to account for non-zero DL terminators. Maria ignores bits 7 and 5, so your terminator check should be for "!(value & 0x5F)".
-* Crossbow. If all graphics appear garbled/in wrong mode then you need to account for non-zero DLL terminators. Maria ignores bits 7 and 5, so your terminator check should be for "!(value & 0x5F)".
+* Crossbow. If all graphics appear garbled/in wrong mode then you need to account for non-zero DL terminators. Maria ignores bits 7 and 5, so your terminator check should be for "!(value & 0x5F)".
 * Planet Smashers. If the background starfield is replaced by glitched graphics, you aren't checking the entire 8000-BFFF range for the bankswitch hotspot. This game uses the BFFF hotspot.
 * Alien Brigade. Corruption in the main screen can be caused by missing or incorrect DMA cycle penalties, whenever lots of objects are displayed in this game.

← Older revision		Revision as of 12:09, 9 May 2024
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	* Klax. If the game starts up with black screen. you might need to change where the emulator starts in the screen, similar to Pole Position II. The Klax proto has a race condition, and has hit-or-miss startup on (some) real consoles too.		* Klax. If the game starts up with black screen. you might need to change where the emulator starts in the screen, similar to Pole Position II. The Klax proto has a race condition, and has hit-or-miss startup on (some) real consoles too.
	* Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.		* Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.
		+	* Legend of Silverpeak. (homebrew) If the game crashes, you need to bankswitch to bank 0 prior to starting emulation.
		+	* E.X.O. (homebrew) If some musical notes are silent or off-key, the pokey emulation needs cycle-accurate emulation of 16-bit joined channels, 1.79Mhz audio channels, two-tone, and "low pass" filtering. See the pokey section of [https://www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf The Altirra Hardware Reference Manual]. Accurate pokey emulations, for reference source, include Altirra (original), MAME/A7800 (original), JS7800 (prosystem derived).
		+	* A.R.T.I. (homebrew) If some musical notes are silent or off-key, the pokey emulation needs cycle-accurate emulation of 16-bit joined channels, 1.79Mhz audio channels, two-tone, and "low pass" filtering. See the pokey section of [https://www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf The Altirra Hardware Reference Manual]. Accurate pokey emulations, for reference source, include Altirra (original), MAME/A7800 (original), JS7800 (prosystem derived).

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 * Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.
 * BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.
-* Pole Position. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.
+* Pole Position II. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.
 * Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.

← Older revision		Revision as of 01:23, 21 January 2024
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	* BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.		* BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.
	* Pole Position. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.		* Pole Position. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.
		+	* Tower Toppler. If graphics are striped and ugly, it's due to missing composite video effects. On a composite video display, pixels that alternate intensity at 320 resolution should appear as a continuous area of "artifacting" color.

← Older revision		Revision as of 01:12, 21 January 2024
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	* Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.		* Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.
	* BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.		* BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.
		+	* Pole Position. If the track selection by joystick only allows selection between tracks 2 and 4, it's due to a race condition that is won on a real console. Starting the emulation at vblank, instead of the top of the visible screen, should allow track selection to work correctly.

← Older revision		Revision as of 01:07, 21 January 2024
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	* Ace Of Aces. If the top line of sky bounces around, it means that DMA cycle penalties or timing aren't accurate.		* Ace Of Aces. If the top line of sky bounces around, it means that DMA cycle penalties or timing aren't accurate.
	* Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.		* Karateka. If during the second enemy stage, there is flickering in the bottom right area and/or the power meter, it means that DMA cycle penalties or timing aren't accurate.
		+	* BallBlazer. If the music track is missing a voice, it's likely the Pokey random number generation is missing or broken.

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 * Rikki & Vikki.  Sound effects volume too low or too high.  Difficulty switch settings control TIA (Sound effects) amplitude.
 * Crazy Brix.  Controls not responding, can't start a game, or game freeze.  Check difficulty switches, tells game what controller types to expect.
-* Armor Attack II.  Second button does not accelerate vehicle.  Difficulty switch setting toggle between pressing UP on joystick or Button 2 to accelerate.
+* Armor Attack II.  Second button does not accelerate vehicle.  Difficulty switch setting toggle between pressing Up on joystick or Button 2 to accelerate.
 * Galaxian.  Player's ship fires too fast or too slow.  Shot speed determined by difficulty switches.
 * Plutos.  Always starts a 2 Player game.  Difficulty switch settings determine whether 1 Player or 2 Players simultaneous game.