Some CRT tubes lose beam focus as they age. The CM-11 is supposed to be quite good as far as CGA monitors go

This monitor is in very good condition and looks like it was hardly used at all. I should clarify. It's fine in 40-column modes, but 80-column text is not so good.

I had heard various references on the net that color 6 (brown) is very hard to distinguish from red on a real CGA monitor and I can verify this to be true. It all looks uniformly red.

unlike, say, the CM-5 with its monster dot pitch from hell

The CM-5 had (I think) a stock 13" color TV tube, which of course is grainy sh*t. Actually the 5153 had better dot pitch than the Tandy monitors or the PCjr display.

80 video standards sure offered plenty of exciting ways to get an ocular migraine, but CGA could've been worse... at least it wasn't interlaced.

I don't think interlacing was ever used much except on some early VGA cards which used it to fudge 1024x768 (it was really 512x768 and used displaced scanlines ala TVs)

kao wrote:

This monitor is in very good condition and looks like it was hardly used at all. I should clarify. It's fine in 40-column modes, but 80-column text is not so good.

I had heard various references on the net that color 6 (brown) is very hard to distinguish from red on a real CGA monitor and I can verify this to be true. It all looks uniformly red.

From recollection, and from photos and videos seen online, real CGA monitors could differ wildly when it came to color 6 - on some it's very close to red, others have a very distinct brown. Something that could be expected, since the card sends out digital "dark yellow" (TTL IRGB 0,1,1,0) and it's up to the monitor to tone down the green.

Never actually owned a true CGA RGB monitor, mind you... I've seen them in action but my memory might be dim. My childhood XT clone used a setup similar to the Compaq Deskpro: the display board could do either CGA or MDA (toggled by a command-line utility), on a green-screen monitor that took both frequencies. 80-column text looked sharp even in CGA mode, since it was monochrome - no RGB dot triads to fuzz things up.
That computer was upgraded to EGA later on. Low-res 80-column text still looked great, but then again the hi-res monitor was probably much crisper than your average CGA display.

I don't think interlacing was ever used much except on some early VGA cards which used it to fudge 1024x768 (it was really 512x768 and used displaced scanlines ala TVs)

Was thinking of non-PC displays too... take the Amiga for instance - technically superior, but not always easy to look at.
I used to have a SVGA card just like that though. Played Moraffware games at 1024x768 interlaced, and the 25 Hz flicker was absolutely atrocious.

From recollection, and from photos and videos seen online, real CGA monitors could differ wildly when it came to color 6 - on some it's very close to red, others have a very distinct brown. Something that could be expected, since the card sends out digital "dark yellow" (TTL IRGB 0,1,1,0) and it's up to the monitor to tone down the green.

In the old CGA composite thread, Servo posted a picture of his CM-5 running King's Quest and brown was clearly distinguishable from red. In addition, this screenshot of Dig Dug http://www.pcmuseum.ca/details.asp?id=100 is fuzzy, but you can still tell the two colors apart. I had always assumed the CM-5 and CM-11 had the same circuitry (just different picture tubes), yet on my CM-11 red and brown all look like one continuous color.

I used to have a SVGA card just like that though. Played Moraffware games at 1024x768 interlaced, and the 25Hz flicker was absolutely atrocious.

I wonder what would happen if you used that on an LCD monitor? I'm guessing it would just do the same thing as HDTVs and display the interlaced signal as progressive scan.

Software gets slower more rapidly than hardware gets faster... due to bloat! That's why I'm diggin' it backwards! I see the modern slowpokes and wonder: WHY all the bloat?
As of CGA, it was an AWKWARD device, but I can clearly see two different "brightness modes" where the mode is defined by toggling the blue bit. Rick Dangerous 2 changes the blue bit for snow levels. I can't wait for CGA_M option to be added to Machine.