MAME Emulation
Re: MAME Emulation
How do your palette mappings compare to running XRoar with "-machine-palette dragon64"? That palette was created by measuring actual output voltages from the VDG on a running machine. If it seems close, maybe you could derive "precise" vaues from there.
Re: MAME Emulation
Thnaks, i already recompiled it.
I rolled back to MAME 208 (22 April) with the latest 2 fixes.
which also has the incorrect NTSC artifacting on PAL machines.
With old and cheap TV modulators, i am sure there will be discrepances in colour palettes between machines.
If cost wasn't an option in prodution at the time, i am sure every Dragon would have had true sharp RGB output.
Please consider tweaking Black & White (dark/light grey).
so i do not need to re-compile with every new release.
And yes please, show me all the files you changed.
I am, you are, we are, they're not...
Re: MAME Emulation
If I push up the contrast on Gimp, I can get close to your colours.
Did you measure the chip output directly? I ask because then you have some resistors and the circuitry that generates the composite signal output, so I guess the signal is greatly modified from the source.
I got my colours from a composite video capture device, capturing areas and averaging the colours. I know it's far from perfect but the colours are very close to what I see on the capture device and on my tv.
Here are my modifications:Please consider tweaking Black & White (dark/light grey).
so i do not need to re-compile with every new release.
And yes please, show me all the files you changed.
https://github.com/mamedev/mame/pull/4980/files
The only files changed are /src/devices/video/mc6847.h and /src/devices/video/mc6847.cpp.
It would be nice to be able to specify a custom palette, for example. But I feel that would be part of a larger discussion.
Re: MAME Emulation
I'm trusting your judgement on the colours as I have nothing to compare them with, they should match the real hardware which is what you've done, though I'm not sure how good a reference point a composite output would be. If XRoar uses measured output then there's probably still room for improvement.
I was actually surprised at how quickly your changes were merged, as I was expecting some internal discussion beforehand. As the MC6847 is only used in a handful of machines it was probably considered relatively safe.
A custom palette in MAME is a definite no. I'm not even sure about how valid the existing artifacting options are, a real MC6847 doesn't have a switch for these options.
Re: MAME Emulation
The XRoar values for that palette (not used by default) were measured at the output of the chip, yes.
But you absolutely can't apply one set globally - the reason those values are so different from the data sheet "ideal" outputs are because in a Dragon, the loading on the output is quite significant. I remember taking similar measurements on a (PAL) CoCo, and they were a lot closer to the "ideal" (which was also obvious from the display).
But you absolutely can't apply one set globally - the reason those values are so different from the data sheet "ideal" outputs are because in a Dragon, the loading on the output is quite significant. I remember taking similar measurements on a (PAL) CoCo, and they were a lot closer to the "ideal" (which was also obvious from the display).
Re: MAME Emulation
On top of that, artifacting and colour blend happens on the tv set and not on the video chip or the computer.
The good thing is that anyone can contribute new values to the source code and I consider this a first step.
The good thing is that anyone can contribute new values to the source code and I consider this a first step.
Re: MAME Emulation
with one of these NEW updates, the extension slot command-line got broken.
this used to boot the dragon32 machine without DDOS.
mame dragon32
and required this to turn it on.
mame dragon32 -ext dragon_fdc
it's always enabled now.
this used to boot the dragon32 machine without DDOS.
mame dragon32
and required this to turn it on.
mame dragon32 -ext dragon_fdc
it's always enabled now.
I am, you are, we are, they're not...
Re: MAME Emulation
DDOS has been the default cartridge for many years now, nothing has changed.
Re: MAME Emulation
Yes, but now the ddos rom is mandatory and the system will not boot without it.
Re: MAME Emulation
The dragon32 driver has specified dragon_fdc as the default ext device for at least 4 years. I tried mame dragon32 in the 0.209 release and DDOS loaded, which version is it not the default? To start without DDOS you could mame dragon32 -ext pak, which is essentially an empty cartridge.