hey all,
I'm not a collector of old systems (...yet?...), and it seems like the answer to my question can't easily be found online, so here I am on this fine forum.
Basically I'd like to know what the 16 CGA colors look like when translated into 16 monochrome shades.
The setup I'm talking about is a CGA/MDA dual-mode card, driving a TTL monochrome monitor, as was common back in the XT clone days (that was the combination on the first PC I ever used). Most emulators of old PCs don't tackle this kind of thing, so I've starting working on a DOSBox patch myself.. the catch is, I don't know anything about the exact correspondence of each CGA (RGBI) color to the resulting shade of green / grey / amber.
So this is kind of a mini research/educational project for me. All I've been able to find is this:
- An image showing 16 colors on a monochrome green monitor
- A video (maybe the creator posts here? ) of an ATI Small Wonder card displaying CGA graphics on an IBM 5151 - check out 2:31 to 2:47 for the color bars test.
Interestingly it looks like the colors progressively increase in brightness, within each half of the palette... but this doesn't make much sense compared to the relative brightness of each CGA color. e.g., you'd expect color #4 (red) to appear darker than color #3 (cyan).
On the monitor in the first photo, color #6 (brown) is darkened, just like on IBM's color CGA monitors - but all other colors just follow the increasing brightness trend. I'd especially like to know if there were any implementations that worked differently.
I imagine there could've been at least two ways to do the CGA-to-mono conversion... it could either be done by the graphics card (and then sent to any TTL monochrome monitor), or on the monitor itself (if it's dual-mode and accepts color CGA signals). And the exact method could vary between different cards and monitors... so it gets still more confusing.
Here's how you can help:
Thank you for your time.
I'm not a collector of old systems (...yet?...), and it seems like the answer to my question can't easily be found online, so here I am on this fine forum.
Basically I'd like to know what the 16 CGA colors look like when translated into 16 monochrome shades.
The setup I'm talking about is a CGA/MDA dual-mode card, driving a TTL monochrome monitor, as was common back in the XT clone days (that was the combination on the first PC I ever used). Most emulators of old PCs don't tackle this kind of thing, so I've starting working on a DOSBox patch myself.. the catch is, I don't know anything about the exact correspondence of each CGA (RGBI) color to the resulting shade of green / grey / amber.
So this is kind of a mini research/educational project for me. All I've been able to find is this:
- An image showing 16 colors on a monochrome green monitor
- A video (maybe the creator posts here? ) of an ATI Small Wonder card displaying CGA graphics on an IBM 5151 - check out 2:31 to 2:47 for the color bars test.
Interestingly it looks like the colors progressively increase in brightness, within each half of the palette... but this doesn't make much sense compared to the relative brightness of each CGA color. e.g., you'd expect color #4 (red) to appear darker than color #3 (cyan).
On the monitor in the first photo, color #6 (brown) is darkened, just like on IBM's color CGA monitors - but all other colors just follow the increasing brightness trend. I'd especially like to know if there were any implementations that worked differently.
I imagine there could've been at least two ways to do the CGA-to-mono conversion... it could either be done by the graphics card (and then sent to any TTL monochrome monitor), or on the monitor itself (if it's dual-mode and accepts color CGA signals). And the exact method could vary between different cards and monitors... so it gets still more confusing.
Here's how you can help:
- If you have a working setup with CGA graphics on a mono TTL monitor - and a few spare minutes:
Could you post a nice, clear photo of it, showing the 16 color bars? (such as one of IBM's test utilities, or the "color testplate" from Trixter's CGA compatibility tester)
- Any technical info on how the color-to-mono conversion is done? (whether in principle, or with a specific card or monitor)
- Bonus question: the IBM 5155 PC Portable also had CGA graphics, but its monochrome monitor was composite (rather than TTL). Still, I'd also like to know what the 16 shades looked like on the 5155, since it would show how IBM meant it to look.
So if you've got a working 5155, could you post a 16 color bar photo? That would be cool too.
Thank you for your time.