Main > Monitor/Video Forum
Idea: customized videocard BIOS
b3atmania:
--- Quote ---There is no picture difference between a 31KHz mode with software scanlines and a 15KHz mode with hardware scanlines on the same monitor. (The AVGA is still easier to use since you don't need to create any modes yourself but it is rather easy to create custom 31KHz modes on most cards)
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Indeed not much of a difference visually. However, software scanlines require CPU cycles to render. Also because you essentially double the resolution (by interleaving the picture with black lines) you also need a framebuffer twice as large. This means copying a rendered frame to the buffer will take a lot longer. For high-end PCs this might not matter but for ageing scrap hardware this is certainly a consideration.
Silver:
I thought there was more than jsut scanlines making a difference?
Running mame with scanlines on my pc monitor does not seem to look anything like running mame at 15Khz? Looks very pixel-ly...
SirPeale:
I'm still waiting for Andy to put the technology he uses in the J-PAC in his video amp. He said at one point that he'd be doing it, but not yet. It's for a project (actually, a series of projects) that I don't need many inputs for (needs seven inputs, so I hacked a keyboard) so a J-PAC is way overkill.
Eventually I'll probably just have to give up waiting, and make a timer circuit for monitor delay.
wpcmame:
--- Quote from: Silver on March 09, 2005, 07:38:33 am ---I thought there was more than jsut scanlines making a difference?
Running mame with scanlines on my pc monitor does not seem to look anything like running mame at 15Khz? Looks very pixel-ly...
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That is because pc monitors got much finer dot-pitch. The picture wouldn't look any more arcade-like if you could run your pc monitor at 15KHz.
How arcade-like the picture look depends on the monitor tube, not on the electronics controlling it.
When a monitor runs in 15KHz it skips every second line but when using software scanlines, every second line is black. Unless there is a difference between not drawing a line and drawing a black line the picture is the same.
desmatic:
--- Quote from: Peale on March 09, 2005, 07:52:11 am ---I'm still waiting for Andy to put the technology he uses in the J-PAC in his video amp. He said at one point that he'd be doing it, but not yet. It's for a project (actually, a series of projects) that I don't need many inputs for (needs seven inputs, so I hacked a keyboard) so a J-PAC is way overkill.
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No doubt. A stand alone protection circuit would certainly be a great toy.
For those considering dumping the bios, yes, it's easy to do. The rage3d folks have been doing it for a while now, and back when a Radeon 32MB DDR was hot stuff, I actually wrote a bootdisk for the rage3d guys that automated the whole thing. Anyways, my recommendation to anyone considering it, get the orginal ArcadeVGA. Aside from the selfless reasons (supporting Andy's time investment) there's also the selfish ones to consider. A lot of goofballs who didn't know what they were doing flashed the wrong models and killed their cards. Not to mention, the retail version of the card with an identical chipset (assuming your clever enough to identify it) will cost you pretty much the same and guess what? It won't work as well if it uses an inferior DAC. So why bother?
As far as the calculations go. I've finally finished writing a modeline calculator for DOS/Windows/Linux, though I haven't had the time yet to test it fully. Its calculations are accurate to whatever a double on your OS is, and there are NO rounding errors for fixed frequency calculations, meaning its more accurate than the DAC on your video card, which should be the only limiting factor. It was written with only one thing in mind, MAME and arcade monitors. Sourceforge project lrmc (low resolution modeline calculator). I've just got a Wellsgardner k7200, which I'll be testing the 15kHz calculations on for a number of video cards. I've tested the output already using an ossilloscope and so far everything's worked nicely. The configuration I'm using is totally new and different from anything out there. I'm not testing it on an open source driver, I'm actually using Nvidia's Linux driver to run MAME at 15kHz, meaning no more waiting for, or debuging open source drivers. If you've got an Nvidia card, you should be all set. PClock mins are a mute issue as well, as long as you're using advance MAME. If you know me, you'll also know that you can rest assured that not a single pixel has been neglected, mistreated, or forgotten. Aspect ratios are correct for underscanned modes, it supports an infinite number of totally independant modeline formats (which will let you take full advantage of D9200 type monitors), you can also pick your modeline preference, from best picture, to best vsync, or best combination.