05345: a2600 [dodgeem, haunted]: Assorted issues related to 6502 CPU

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
05345	Core	Major	Always	Oct 30, 2013, 20:45	Sep 26, 2015, 19:38

Tester	Tafoid	View Status	Public	Platform	MESS (Official Binary)
Assigned To		Resolution	Fixed	OS	Windows Vista/7/8 (64-bit)
Status [?]	Resolved			Driver	atari/a2600.cpp
Version	0.150	Fixed in Version	0.166	Build	Normal
		Fixed in Git Commit		Github Pull Request #

Summary	05345: a2600 [dodgeem, haunted]: Assorted issues related to 6502 CPU
Description	Suspected to timing issues of the core, the following happens: Dodge Em (dodgeem) - Audio is incorrect. Wrong types of sound play at wrong times. Haunted House (haunted) - Graphics are offset - impossible to play correctly. Eye should start on the right side.
Steps To Reproduce
Additional Information	All issued traced to either initial change of the new 6502 core or the IRQ fixes shortly after (r18875, r18880)
Github Commit

Flags
Regression Version	0.147u3
Affected Sets / Systems	a2600 [dodgeem, haunted]

Attached Files	HH-FIXED.zip (3,481 bytes) Sep 16, 2015, 13:40 Uploaded by trebor Hacked version which corrects the instruction at $F44F, and it runs as expected in MESS.

No.10071 wilbert Developer Dec 15, 2013, 19:34	Reimplemented FE mapper in revision 26624, fixes decathln.
No.10085 wilbert Developer Dec 20, 2013, 18:15	For dodgeem the instructions executed is exactly the same between the old and new cpu core. So I am guessing the incorrect sound there is caused by ghost reads of writes.
No.12032 trebor Tester Sep 16, 2015, 13:37	Regarding Haunted House...Courtesy of Mike Saarna: ""Reading a write-only register on most 2600s returns the last value on the bus, and the last value on the bus is the last byte in the opcode. The HH programmer made a typo. At $F44F the game is sutracting using the value in $0f, instead of subtracting using the literal value $0f. Since the last byte of the opcode is $0f, most 2600s will pull this value and wind up working as intended. But on 1 out of 100 2600s, the "last value on the bus" result doesn't happen. Same is true for emulators that don't similarly handle reads from write-only registers. I've attached a hacked version of the HH bin which corrects the instruction at $F44F, and it runs as expected in MESS. The 7800 has the same bus effects in places too, BTW."
No.12033 trebor Tester Sep 16, 2015, 13:43	Sorry old habit, MESS=MAME :)
No.12034 trebor Tester Sep 17, 2015, 01:21	Regarding Dodge 'Em...Again, courtesy of Mike Saarna: "Dodge Em has a similar program error... actually 2 of them. One at $F149, and another at $FBAC. The latter one is responsible for messing up the sound."
No.12048 Tafoid Administrator Sep 26, 2015, 19:38	https://github.com/mamedev/mame/commit/80b274e7ed97be04821cb6658a154ea11203b8ff a2600: new 6502 PC=cur inst, old 6502 PC=prev inst (MT 5345) [Mike Saarna, Trebor, R. Belmont]