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Re: Why this bad résolution in some games? (720X400)

Posted on 2018-03-04, 17:22

Ok! 720x400 was a bit strange to me (why not 640x400?). And yes the games run fine and seem to have a correct aspect ratio. Thanks! That's because 320x200 graphics mode looks identical to the monitor as text mode which is 720x400 and nearly all TFT monitors sample that as 720x400 to display pixel …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-20, 20:59

Allright thanks for the info! Any recommendation of the value the pulldowns must be? Do they need to go to pins 2-3-4-5-6-7 or only needed for the secondary/intensity pins 2-6-7 ? The rule is not to leave any input of CMOS chip unconnected. This means also situation where the cable is disconnected …

Re: Subtle Waves on Old Tseng VGA Card

Posted on 2018-02-20, 17:20

Some cards have this issue. What I think happens is that some ripple on power supply lines gets coupled to sensitive video circuits, such as DAC voltage reference. The ripple might come from outside the video card (like power supply, another card nearby it, or hard drive etc) or from the card itself …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-19, 21:34

But I see that there's no pulldown resistors on the converter DB9 connector, so if the EGA card tri-states the unused pins or it is connected to CGA card, the voltages can float at indeterminate levels as there is nothing connected to them. This shouldn't be a problem because the sync levels …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-19, 19:53

Checking with my meter, pin 2 is definitely NOT grounded in CGA or EGA modes. It reads 141 mV in CGA mode and drops slightly to 140 mV in EGA mode. This doesn't seem right. Pin three varies between 150 to 160 mV. In the IBM EGA adapter there is a real jumper that selects if pin 2 is wired to either …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-17, 19:15

most of the people know the brown color is logic tweaked on the cga monitor but I can tell from my observations that yellow is also tweaked, It does not have bright for the blue channel, otherwise it would be a little washed out. Where did you read this? Yellow is the same as other "bright" colors …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-17, 00:50

I've been calculating stuff. Does these calculations explain why some colors look off? VGA input is terminated into 75 ohms, signal voltage 700mVpp. EGA has two bits per color component, and so the EGA palette in 6-bit VGA DAC world is 0, 21, 42, 63, and modern 8-bit world 0, 85, 170, 255. So …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-09, 08:51

^ shouldn't the refresh rate at least be correct on the OSD? I need to find something that outputs a 60hz signal for sure, maybe I will try with the dreamcast to make sure the scaler is reporting things fine - at least refresh. Oh, you mean the monitor reports 75Hz? What is generating the test …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-08, 22:17

^ I have my doubts about that, the scalers in modern sets are not "dumb" anymore like 10+ years ago. At any rate that's really a side-discussion - I have reported my experience here , whether it's an issue or not we will see :blush: OK - but I think others might find the information how TFT …

Re: MDA/CGA/EGA to VGA Converter Released!

Posted on 2018-02-08, 18:14

@retrocanada76 I just updated to the latest firmware but for me low-res EGA is still reported by my monitor as 720x400@70hz edit: just checked 720x480 mode, the monitor reports it as 640x480 for some reason but this means that I don't get 720x480 on low-res ega games with the new fw It's analog …

Re: Does ISA video card need IRQ/DMA/PORT?

Posted on 2018-01-30, 16:27

Usually this is not mentioned because usually it is not a problem - nearly all systems have a video card (there might be exceptions) and thus other cards are made to support only such resources that would conflict with video cards. ISA video cards never use DMA, that's for sure. They also do not …

Re: Capturing Accurate Voodoo1 Screenshots

Posted on 2018-01-16, 20:44

You can't take accurate screenshots from a Voodoo card, as the RAMDAC does additional filtering. There's no way to get the final image, unless you feed it into a VGA capture device. I see no filtering happening *in* the ICS5342 RAMDAC. If there is digital filtering (upsampling) it happens before …

Re: When Does VGA latch the start address register

Posted on 2017-12-17, 14:15

I've made a little test program to determine when it is latched. I've only tested on one system so far, so other systems may behave differently. It looks like the start address register is latched pretty close to (or exactly at) the moment when the vertical retrace bit (bit3) in port 3da goes high. …

Re: UART Tx

Posted on 2017-12-15, 09:07

You could have told they are MIDI devices. Did you even tried reading the manuals? There is no single UART Tx pin, but a pair of pins. Standard MIDI output is not a single output pin referenced to ground, but differential output, pin 4 sourcing current and pin 5 sinking current. 99% of the time pin …

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