Viewing Issue Advanced Details
|ID||Category [?]||Severity [?]||Reproducibility||Date Submitted||Last Update|
|06772||Gameplay||Major||Always||Nov 22, 2017, 20:31||Nov 23, 2017, 14:42|
|Tester||MrGW||View Status||Public||Platform||MAME (Self-compiled)|
|Assigned To||hap||Resolution||Fixed||OS||Linux (64-bit)|
|Version||0.191||Fixed in Version||0.192||Build||64-bit|
|Summary||06772: Dragon machines run too fast!|
Best guess is this in dragon.cpp:
static MACHINE_CONFIG_START( dragon_base )
// basic machine hardware
MCFG_CPU_ADD("maincpu", M6809E, DERIVED_CLOCK(1, 1))
My MAME-fu is poor, but looks like CPU clock being derived from PAL colour
subcarrier frequency. Of course, CPU rate should be a subdivision of
SAM rate depending on its settings as per CoCo.
|Steps To Reproduce||Reproduce by just running anything on a dragon32 or dragon64.|
|Additional Information||Ciaran Anscomb (XRoar author) discovered this issue and provided his initial analysis of what he believes is causing the issue.|
|Flags||Verified with Original|
|Affected Sets / Systems|
|There are no relationship linked to this issue.|
Nov 22, 2017, 22:20
It looks like the motherboard has 2 XTALs: 4.443619MHz(PAL subcarrier), and 14.2180MHz(main).
Pippin(Dragon prototype) and the 1st version of Dragon 32 Mark I have a 14.31818MHz main XTAL instead. MAME doesn't emulate these machines(yet?). 2nd version of Dragon 32 Mark I, Mark II, and every other Dragon after that, has a 14.2180MHz main XTAL.
photos here: http://archive.worldofdragon.org/index.php?title=Motherboard_Pictures
Nov 22, 2017, 22:34
edited on: Nov 22, 2017, 22:35
It's fixed now.
Note: don't be misled by MAME's reported CPU speed of 3.55MHz. The M6809E has an internal /4 divider, making the practical CPU speed 0.89MHz.
Nov 23, 2017, 14:42
|Thanks for fixing this one too, hap!!|