EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Ampera on December 23, 2016, 05:33:23 am
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I currently have in my possession an AM486-DX4-100(@120) based VLB machine with an S3 Trio32/Diamond Multimedia Stealth SE. It has support for resolutions up to 1280x1024, but any resolutions over and including 1024x768 reduce the refresh rate so low, none of my LCD panels can display it, and I do not have a CRT on my hands.
I want to know, does there exist a device that can take the refresh rate of video (RGB/VGA, not SCART type!) and multiply it by 1.5 times. This means 43hz becomes 61.5 (Or close to)hz, etc. Either that or a device that will constantly output 50, 60, or 75 hz regardless of what is inputted.
No clue where I would even look for such a device, I hope it exists in some manner.
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You can get converters/scalers and scan converters, but they aren't cheap and they are usually used to convert one signal type into another (such as composite video to VGA etc...). I haven't seen a VGA-to-VGA device. If you do find something, you're likely going to have to spend several hundred dollars at least, you may as well just get yourself a better video card for that kind of money.
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Do any of your LCD's have hdmi inputs? If so you could try a simple vga-hdmi converter.
Tim
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You should be able to easily pick up a cheap ISA bus graphics card on ebay with a decent refresh rate. The VLB bus is meant to be backwards compatible with the ISA bus.
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You can get converters/scalers and scan converters, but they aren't cheap and they are usually used to convert one signal type into another (such as composite video to VGA etc...). I haven't seen a VGA-to-VGA device. If you do find something, you're likely going to have to spend several hundred dollars at least, you may as well just get yourself a better video card for that kind of money.
Unfortunately the Stealth SE is one of the better VLB graphics cards, it's by no means a bad card.
I thought about getting a VGA to Component video converter for use with something like a capture card, but I don't know if mine supports low resolutions.
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You should be able to easily pick up a cheap ISA bus graphics card on ebay with a decent refresh rate. The VLB bus is meant to be backwards compatible with the ISA bus.
Impossible. The ISA bus would be too slow to support 60hz video at that high of a resolution. It's just too slow. The VLB standard was designed primarily for graphics cards. I also want to use the Stealth SE as it is a very good card, there isn't a single ISA graphics card in existence that is better than the Stealth SE, it's just a technological fact.
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This means 43hz....
Arrrg, if I remember from those days, when they say 43Hz, they mean it's 85hz laced, technically 43 frames per second. This mode was used since the video ram wasn't fast enough for full 65536, or, 16m color at 60hz progressive. You wont find a video scaler, or, even a VGA video sampler which would recognize and convert this particular ancient video mode today. (I just potentially saved you some time and $$$ if you were considering the expense of a video scaler)
If possible, first try lowering the color output to 65536, then, 256 colors, or 16 colors, then, if you are lucky, you will get 60hz progressive at 1280x1024. Otherwise, you will need a new graphics card.
Are you using DOS, or Windows95/98?
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I think the easiest option is to just back it down to 800x600 (which was still rather high for those days). Most applications and games back in those days were designed for 640x480 (or less) with a few games preferring SVGA (800x600) graphics modes. Anything higher was usually for those who worked in graphics.
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The only possible way to upscale that is by increasing the frame rate by doubling, say, every frame, or every other frame, or something like that -- inevitably, you incur at least a half (or so) frame of delay, or more.
A frame's worth of delay isn't too bad, but more than two or three frames is quite noticeable in critical applications! (On the other hand, dozens of frames are readily tolerable in streaming video, as long as the audio is delayed a similar amount.)
Tim
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You should be able to easily pick up a cheap ISA bus graphics card on ebay with a decent refresh rate. The VLB bus is meant to be backwards compatible with the ISA bus.
Impossible. The ISA bus would be too slow to support 60hz video at that high of a resolution. It's just too slow. The VLB standard was designed primarily for graphics cards. I also want to use the Stealth SE as it is a very good card, there isn't a single ISA graphics card in existence that is better than the Stealth SE, it's just a technological fact.
I think chipsets like the S3 Virge could do 1280x1024 at 75hz but with 256 colours. If you want 16 bit color, then that is a problem.
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Many of your posts have some basic confusion that is just too deeply embedded to disregard. In this case it's "ISA bus has too low bandwidth to support high refresh rates". You fail to appreciate that a graphics card doesn't refresh the monitor from the system memory, but from its own VRAM, and so it is irrelevant what the system bus is. How someone could assemble a computer from components and not know that, I can't understand.
The Matrox Impression ISA card supports 1024x768 @ 70 Hz, for example. The Hercules SuperStation ISA card supports 1280x1024 @ 72 Hz. The Impression Plus 220 ISA card does 1600x1200 @ 85 Hz.
With respect to your original question, frame-rate conversion is possible but it has many drawbacks. If the input and output frequencies are not an integer multiple, "pull-down" is required which results in stuttering motion. The converter also needs at least 2 full frame-buffers, plus ADCs and DACs, which are very expensive at high frequencies.
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Many of your posts have some basic confusion that is just too deeply embedded to disregard. In this case it's "ISA bus has too low bandwidth to support high refresh rates". You fail to appreciate that a graphics card doesn't refresh the monitor from the system memory, but from its own VRAM, and so it is irrelevant what the system bus is. How someone could assemble a computer from components and not know that, I can't understand.
The Matrox Impression ISA card supports 1024x768 @ 70 Hz, for example. The Hercules SuperStation ISA card supports 1280x1024 @ 72 Hz. The Impression Plus 220 ISA card does 1600x1200 @ 85 Hz.
With respect to your original question, frame-rate conversion is possible but it has many drawbacks. If the input and output frequencies are not an integer multiple, "pull-down" is required which results in stuttering motion. The converter also needs at least 2 full frame-buffers, plus ADCs and DACs, which are very expensive at high frequencies.
lol, forgot about that one.
It still would be way slower than any VLB card there is. ISA stopped being useful for video before it even had a replacement.
Yea, maybe I'll stick to 800x600. The odd thing is that the resolution 1152x864 in Windows 3.11 works fine. The strange part is that this is an XGA mode derived from a special S3 driver for Windows 3.11.
In other interest, does anybody know of a VLB (ISA may be fast from the card up, but without DMA and a 4.77 mhz bus speed, it's too slow for even reasonable games (Main purpose of the machine)) card that doesn't do this? I know for a fact that the Mach64 does this as I have two of them implanted in a couple IBM servers and they do this too.
Possibly something like a Trio64V/V+? (I think that's the chip).
And yea, the refresh rate isn't derived from system memory access, rather from video memory access, but the time to update the screen would be too slow to be useful for a DX4-100/120.
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I currently have in my possession an AM486-DX4-100(@120) based VLB machine with an S3 Trio32/Diamond Multimedia Stealth SE. It has support for resolutions up to 1280x1024, but any resolutions over and including 1024x768 reduce the refresh rate so low, none of my LCD panels can display it, and I do not have a CRT on my hands.
TwoOfFive isn't talking about game rendering rates. His video card isn't actually capable of generating the pixel clock necessary at higher resolutions to achieve the minimum progressive 60hz refresh rate his monitor requires to begin to show an actual image.
With older video cards, the video memory on the board was just too slow to send 16 or 32 bits / pixel to achieve the speed necessary to continuously draw that non-stop picture at higher resolutions. But these video cards allowed, many of them, when operating at 256 colors, or, 8 bit per pixel, double the clock rate for the video DAC compared to 16 or more bits per pixel.
Now as for video scalers, yes they should do what TwoofFive wants, except, they are usually designed for NTSC 480i, Pal, 1080i, 720p, and, all PC progressive video modes 60hz and above up to their limit. If you find a video scaler available today which supports the 43hz, of sometimes known at 85i, not 85hz progressive, or 85p which many support, including the one I built, as a supported RGB video input mode, you have got the luck of the gods.
My home made scaler of a few years back, (OK is a really expensive fully featured network controllable unit...)
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I currently have in my possession an AM486-DX4-100(@120) based VLB machine with an S3 Trio32/Diamond Multimedia Stealth SE. It has support for resolutions up to 1280x1024, but any resolutions over and including 1024x768 reduce the refresh rate so low, none of my LCD panels can display it, and I do not have a CRT on my hands.
TwoOfFive isn't talking about game rendering rates. His video card isn't actually capable of generating the pixel clock necessary at higher resolutions to achieve the minimum progressive 60hz refresh rate his monitor requires to begin to show an actual image.
With older video cards, the video memory on the board was just too slow to send 16 or 32 bits / pixel to achieve the speed necessary to continuously draw that non-stop picture at higher resolutions. But these video cards allowed, many of them, when operating at 256 colors, or, 8 bit per pixel, double the clock rate for the video DAC compared to 16 or more bits per pixel.
Now as for video scalers, yes they should do what TwoofFive wants, except, they are usually designed for NTSC 480i, Pal, 1080i, 720p, and, all PC progressive video modes 60hz and above up to their limit. If you find a video scaler available today which supports the 43hz, of sometimes known at 85i, not 85hz progressive, or 85p which many support, including the one I built, as a supported RGB video input mode, you have got the luck of the gods.
My home made scaler of a few years back, (OK is a really expensive fully featured network controllable unit...)
Another question is what CAN display it? When I said I don't have a CRT on hand that was half true. I do not have a CRT that can either display resolutions that high (I have a PAL display and that's it) or it's already part of an AIO system (iMac G3). I don't want to take on another CRT since once you have them, you have to find an idiot to take it off your hands. They are impossible to get rid of.
And no, even at 256 colours I can't reach anything above 800x600.
But as I said the very strange part is that 1152x864 DOES work. I need to reinstall Windows 3.1 and figure out what refresh rate it outputs, but if it can do 1152x864, why can't it do 1024x768? I looked in OS/2 and it displays all the modes and refresh rates possible, but 1152x864 is not on that list, only in Windows 3.1, and only with the Windows 3.1 display driver.
Oh well, at least it's Win3.1, could be more useless programs it only works with. ^-^
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There is one thing about the really old VGA plug standard. Before the 'DDC' which used 2 wires on the VGA plug to tell windows which modes your monitor supports, there was a system which shorted 2 or 3 pins to VCC of GND by the monitor to tell the PC which modes it can do. 1152x864 was not a standard video mode at that time, so it may only start at 60hz.
What this means is that 'possibly', your video card can go a little faster, like 1024x768 at 60hz, but, because of the older style sense pins on the VGA connector of your video card & may be restricting the scan rate of the standard older video modes ignoring the 1152x864 which wasn't in the feature list of those days. If your video card supports DDC and your monitor's DDC chip is being properly read, then this is not the case.
Google up VGA Connector ID pins or VGA DDC and see if you can cut or tap out the data lines on a cheap scrap VGA video cable you have lying around and see if windows allows some new video modes. If I remember, I used to cut the DDC lines in the past to open up all the video modes on my old Matrox/ATI cards before they added a feature to ignore the DDC in their video driver advanced control panel.
Pinout here: https://en.wikipedia.org/wiki/VGA_connector
I used to cut pins 12 and 15, or, used a BNC rgb cable connection to my monitors which had no DDC connections.
Old fashioned video mode limiter: https://en.wikipedia.org/wiki/Display_Data_Channel
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back in the days when I had an Amiga 500, there was a device that addressed this probblem: https://en.wikipedia.org/wiki/Flicker_fixer
No idea if that would work on anything else than an Amiga though...
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back in the days when I had an Amiga 500, there was a device that addressed this probblem: https://en.wikipedia.org/wiki/Flicker_fixer
No idea if that would work on anything else than an Amiga though...
Ohhh, I remember those days well....
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Another thing to keep in mind is that LCD displays can refresh at much lower rates than CRTs without causing flicker. Some high-resolution LCDs run at 13 Hz (https://en.wikipedia.org/wiki/IBM_T220/T221_LCD_monitors). Too slow and you can lose track of the cursor, but there's no flicker.
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Another thing to keep in mind is that LCD displays can refresh at much lower rates than CRTs without causing flicker. Some high-resolution LCDs run at 13 Hz (https://en.wikipedia.org/wiki/IBM_T220/T221_LCD_monitors). Too slow and you can lose track of the cursor, but there's no flicker.
That was a rather unusual display. And it was only the interface that supported 13Hz (most likely because at that time there was no fast enough digital video interface available), the display itself was always refreshed at 41Hz.
Most modern LCD monitors don't support <50Hz, because they don't have an internal framebuffer (unlike the first generation LCD monitors), instead the input signal gets scaled to the screen resolution using the input framerate.
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Most modern LCD monitors don't support <50Hz, because they don't have an internal framebuffer (unlike the first generation LCD monitors), instead the input signal gets scaled to the screen resolution using the input framerate.
Be careful here.... Most LCD screens today do have a memory buffer of a frame. It's needed to convert the number of source video formats and resolutions so it can scale them to the native resolution of the LCD. Some LCD screens today also usually to strobe 1 frame at double your input scan rate, then, strobe a black frame during the next half to get that sub 4ms response refresh speed without any smearing artifacts while playing video a smooth panning camera scenes.
Do not confuse a full size home LCD pc monitors, or TVs which have a set of VGA/DVI/HDMI inputs with one of those small digital only interface industrial units with only a digital flex connector. These usually screens don't support the 50hz because their firmware on their input controller board, which has the scaler and memory, which then feeds the LCD, is only programmed to support speeds and resolutions A-B. If you took a commercial LCD feeding it's flex connector input with 640x480 image while the LCD itself was 1280x1024, you would be left with 1/4 sized picture squished up at the top left hand corner.
Now, there is the all new thing, ok maybe it's be available for a few years now, where the scaling is done in your PC video card & the video card always sends the native to the monitor. There is also the new video game sync modes which only starts refreshing the LCD immediately once a game rendered frame is complete, making your LCD screen run at a random vertical refresh rate of anywhere between 20hz and it maximum capable vertical speed, bypassing any onboard monitor scaling or buffer electronics giving you the fastest possible response time. Yes, this mode has no vertical refresh, it's strobed out with a new picture drawn immediately upon completion of the rendered frame buffer for only a single frame. ( http://www.geforce.com/hardware/technology/g-sync/faq (http://www.geforce.com/hardware/technology/g-sync/faq) )
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Most modern LCD monitors don't support <50Hz, because they don't have an internal framebuffer (unlike the first generation LCD monitors), instead the input signal gets scaled to the screen resolution using the input framerate.
Be careful here.... Most LCD screens today do have a memory buffer of a frame. It's needed to convert the number of source video formats and resolutions so it can scale them to the native resolution of the LCD. LCD screens today also usually to strobe 1 frame at double your input scan rate, then, strobe a black frame during the next half to get that sub 4ms response refresh speed without any smearing artifacts while playing video a smooth panning camera scenes.
For scaling the resolution you don't need a framebuffer. A linebuffer holding a couple of lines is enough.
The more expensive ones probably have a framebuffer for advanced features (like deinterlacing interlaced video), but not the cheap pc monitors.
TVs are a completely different story.
For VGA you don't have a pixel clock, therefore the firmware has to guess the horizontal resolution by looking at Hsync+VSync frequencies and comparing them to build in list of common timings.
That's why CRT monitors support basically any resolution while LCD monitors often have problems if you try to use a less common timing.
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For scaling the resolution you don't need a framebuffer. A linebuffer holding a couple of lines is enough.
Yup, that quest to make things as cheap an junky as possible. In this case, I guess the input boards of desktop monitors have foregone that DDR3 ram chip with the main one for a single all in one chip solution with a few KB of internal line memory.
These screens would flutter like mad if you successfully fed them 1920x1080i, or you could call it 1920x540p with each alternating frame having a back and forth jumping jitter action.