Viewing Issue Advanced Details
ID Category [?] Severity [?] Reproducibility Date Submitted Last Update
08219 Sound Minor Always Feb 20, 2022, 05:31 Sep 2, 2022, 09:37
Tester CYBERYOGI -CO-Windler View Status Public Platform MAME (Official Binary)
Assigned To Resolution Fixed OS Windows 10/11 (64-bit)
Status [?] Resolved Driver
Version 0.237 Fixed in Version 0.247 Build 64-bit
Fixed in Git Commit ffc0db2 Github Pull Request #
Summary MESS-specific 08219: a800xl: Bass voice missing in "Zybex" game music.
Description In "Zybex" on Atari 800XL there is a flickering line to the left of the screen, and the POKEY music is missing the bass voice! (It happens both in PAL and NTSC Atari, only in NTSC the music plays faster.) Please fix this.

This is what the music should sound like on NTSC (written for PAL, it is originally slower):

(I found the bug in 2021-10-21 in the at that time fresh MAME version, which was 0.237.)
Steps To Reproduce Load the game Zybex and listen to the intro music.
Additional Information
Github Commit
Regression Version
Affected Sets / Systems a800xl
Attached Files
related to 07378Resolved pokey.cpp: Inaccurate distortion playback. 
User avatar
Senior Tester
Feb 20, 2022, 07:47
edited on: Feb 20, 2022, 07:49 is an existing report of the problem. The bass notes are being played in MAME, they are just at a pitch that's something like 2 1/2 octaves too high, i.e. moving at a parallel fifth to the correct bass line due to the unemulated POKEY mode.
User avatar
Feb 20, 2022, 09:47
edited on: Feb 20, 2022, 09:47
"Please fix this." isn't needed in your bug descriptions. It does nothing to help diagnose, fix the problem, or inform the developers. As a reminder, always post the most recent version when posting bugs. It is assumed that all bugs reported have been tested and replicate in the latest release build before being posted. You posting 0.237 as offending MAME version doesn't help and only requires us to test current in which something may be already fixed.

Please do not mix graphic and sound issues together in a bug report. The graphic issue is acknowledged with the machine being flagged with imperfect graphics (colored screen you need to acknowledge before starting the machine in MAME). No need to report bugs like that unless you have noted heavy regression (as per Rules). Please familiarize yourself with reporting rules and help (upper right side "Help" pulldown). Having to explain little things which should be known is becoming tiresome to both remind and to fix.
User avatar
Feb 22, 2022, 06:30
edited on: Feb 22, 2022, 07:14
Is POKEY emulation still imperfect? I always thought its shifregister feedback noise source was used as protection inside early Atari arcade games and so had to be implemented perfectly to make such games work.

(The graphics glitch was minor and not what I complained about. It may even exist on real hardware and get hidden by overscan of an actual CRT monitor. And I would not have complained about an "old" MAME version when I assumed it to be fixed in the current version. (I did not see POKEY things mentioned in recent whatsnew.txt.) My MAME is on a different computer, so I can't quickly check from here if the bug is still valid.)
User avatar
Senior Tester
Aug 28, 2022, 09:54
Improved accuracy of POKEY emulation:

"Zybex" game music sounds better now. Is it fixed?