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Bad video with Tandy 1000

V

vladstamate

Experienced Member
Joined
Dec 2, 2012
Messages
197
Location
Orlando, FL, USA
Ok,

So I finally got a keyboard for my Tandy 1000 and booted it up again. No matter if I connect it to a CGA monitor or a TV (using composite) the video is ineligible. Here are two images attached, one from my CGA monitor and one from the TV. The green one is the CGA monitor. I must add that the longer I let it on the worse the image was on the CGA until after 10 minutes it was just a mess of dots and lines....

So question:

1) Is my CGA dying or is the Tandy bad? I remember connecting it to my PC XT and it was better than that a while ago.
2) Is the composite normal to be that bad? How did IBM ever thought IBM PCjr was ok to connect to TV using composite?!
3) What can I do to actually use my Tandy as in the condition that is now I cannot see anything that I can understand when I type "dir".

photo 1 (3).jpgphoto 2 (3).jpg

Regards,
Vlad
 
IBM meant the composite video output to display in 40-column text mode or 80-column text on small monochrome monitors. It even had a switch on the IBM PC to set that on startup. You can use the DOS command MODE CO40 and your text should be much more legible on the Tandy.

Try some games or graphics and then see how the Tandy does.
 
Thank you, MODE CO40 did indeed make the composite out totally useable and legible. I do not have any games or graphics (unless I can do something with basic). It has a harddisk but no games on it alas (it seems it was used in a highschool, as it has SAT software amongst other things, like word editing and printing software and drivers).

I wish I had a tweener system that worked so I can transfer some software on disks and try the Tandy.

Thanks again,
Vlad.
 
It's hard to tell from the photo, but if that "CGA" monitor is a Commodore or Magnavox/Philips monitor connected via the Tandy's composite output, then switch the monitor into Luma/Chroma (LCA) mode. That will make 80-column mode legible, although it will only be displayed in monochrome. Then if you want to run a game or other program with 40-column text or color graphics, switch it back to composite (CVBS) mode to see it in color.

And if my suspicion about what monitor you're using is correct, then you should really invest in an RGB cable, so you can see the Tandy's video output in its true quality. You can look for a Commodore 128 RGB video cable for your model of monitor, because the C128's RGB video output is the same thing as CGA on a PC or Tandy.

p.s. If you're using the official Tandy version of MS-DOS, then typing MODE TV will switch it into 40-column color composite mode with 200 scan lines. (Normally Tandy's CGA video uses 225 scan lines for text mode, which might go off the top and bottom of the screen when displayed on a TV set.)
 
@vwestlife brings up a good point -- I was wondering if you were actually connected via TTL or if you were running composite to an 'alleged' CGA monitor... there is a difference!

Also not all CGA monitors were made the same. A real IBM 5153 or Tandy CM-11 are heads and shoulders above say, the crappy Tandy CM-5. Many alleged 'cga' monitors are flat out illegible at 80 columns even via TTL. It all comes down to dot pitch, and many cheap CGA displays were just re-purposed TV's with TTL inputs, and as such really not capable of delivering that 640 width the CGA wants in 80 column mode.

... though monochrome composite displays have no such limitations.

Though CGA 80 column text always was kind-of crappy even with the best of monitors -- simply adjusting horizontal and vertical position can greatly impact the output -- which is why anyone who cared about text at the time usually was on a MDA or Hercules card. They weren't just about being cheap.
 
deathshadow said:
Also not all CGA monitors were made the same. A real IBM 5153 or Tandy CM-11 are heads and shoulders above say, the crappy Tandy CM-5.
Click to expand...

The Tandy CM-2 and CM-10 are fine as well. They were predecessors to the CM-11, and also have the fine-pitch, anti-glare display. But avoid the CM-4, because it has the same large-pitch, non-anti-glare display as the CM-5.

And if you come across a CM-1 or CM-8, those are nice monitors, but won't work with the Tandy 1000 series or any IBM or PC clone with CGA; those models were designed for the Tandy 2000 and Color Computer 3, respectively, and use different video standards.
 
I'll allow you the CM-5 was pretty darn crappy...but still had very legible text, even at 80-columns. Nevermind the fact that you could see (without a magnifying glass) the individual colored pixels that made up the white...

Our first home computer back in the day was a 1000SL with a CM-5. Heck, I was just happy my parents sprung for a color monitor!!! Later on, I got a CM-11 from someone...definitely a nicer monitor.

Wesley
 
vladstamate said:
No matter if I connect it to a CGA monitor or a TV (using composite) the video is ineligible.
Click to expand...

For composite connections, the photos you posted look normal. Mode BW80 or CO40 can help clear it up.

If your CGA monitor is connected via the 9-pin TTL RGB port and it STILL looks like that, that's not normal. But for a single composite connection, that's normal.
 
I also used a CM-5 for years on my 1000TL, and found that it was perfectly adequate. I still have mine, though I was able to get a CM-11 later on. The CM-11 is definitely a bit finer, but I wouldn't say it's waaaay better or anything.
 
The fuzzier CM-5 has a side benefit: 320x200 gaming graphics look better, especially those that use 50% bayer/hatch dithers. I see this in the PCjr monitor as well, which is fuzzier than the IBM 5153.

If you work with text more than gaming, then yes, the better monitors are worth the money. But if gaming is the only target, a CM-5 or equivalent is fine.
 
Trixter said:
The fuzzier CM-5 has a side benefit: 320x200 gaming graphics look better, especially those that use 50% bayer/hatch dithers. I see this in the PCjr monitor as well, which is fuzzier than the IBM 5153.

If you work with text more than gaming, then yes, the better monitors are worth the money. But if gaming is the only target, a CM-5 or equivalent is fine.
Click to expand...

Dot pitches:
Tandy CM-5: 0.64 mm
Tandy CM-11: 0.42 mm
IBM 4863 (PCjr): 0.43 mm
IBM 5153: 0.38 mm
 
More Dot pitches for comparison:

IBM 5145: 0.43 mm
IBM 5154: 0.31 mm

Commodore 1701 Composite: 0.64 mm (!!)
Most Amiga era Commodore monitors: 0.42 mm
 
I found my IBM 5153, before I killed it, to be a little too sharp when it came to 160x200 graphics. I saw distinct, unintended color changes between pixels. Whatever its faults, the CM-5 did not show that. However, we have a clear demarcation between dot pitches :

Low end : 0.63-0.64
Median : 0.42-0.43
High end : 0.38 or lower

I am sure the IBM PC Convertible Color Display 5145 was just the IBM PCjr. Color Display put in a new, PS/2 style housing. It uses the PCjr. Display Connector and has a built-in speaker.
 
Too small of a dot pitch is not good for CGA because you begin to see the gaps between the scan lines. That effect is very prominent on my Mitsubishi AUM-1381 Diamond Scan monitor with 0.31 mm dot pitch. That's why some fancy EGA cards "double-scan" CGA from 200 lines to 400 lines, so you don't get that "horizontal blinds" effect. (British old-timers will recall TV sets which used "dot wobble" to achieve the same effect with their old 405-line black & white TV system.)

The cheaper CGA monitors just used ordinary TV-grade picture tubes, which is why they have the big dot pitch and usually no anti-glare coating. But if you think that's bad, try a Tandy VGM-225 VGA monitor with 0.52 mm dot pitch! I remember seeing one in the store and trying to view 640x480 VGA graphics on it was unbelievably fuzzy.
 
vwestlife said:
Too small of a dot pitch is not good for CGA because you begin to see the gaps between the scan lines. That effect is very prominent on my Mitsubishi AUM-1381 Diamond Scan monitor with 0.31 mm dot pitch. That's why some fancy EGA cards "double-scan" CGA from 200 lines to 400 lines, so you don't get that "horizontal blinds" effect.
Click to expand...

I've heard of this so-called "Double CGA", but I was under the impression that it was its own distinct video mode which originated from the AT&T PC6300. Toshiba laptops of the late 80s early 90s also had this mode of 640x400 resolution. I know Microsoft Word, Wordperfect and a few games had support for it. The 640x400x2 resolution I'm talking about wasn't related to EGA, or are we talking about two different modes?

For example, this Toshiba T1000LE showing support for "Toshiba Graphics Mode" which is really monochrome "Double CGA"...

http://www.toshiba-europe.com/computers/products/notebooks/t1000le/product.shtm
 
Last edited:
motley2659 said:
I've heard of this so-called "Double CGA", but I was under the impression that it was its own distinct video mode which originated from the AT&T PC6300. Toshiba laptops of the late 80s early 90s also had this mode of 640x400 resolution. I know Microsoft Word, Wordperfect and a few games had support for it. The 640x400x2 resolution I'm talking about wasn't related to EGA, or are we talking about two different modes?

For example, this Toshiba T1000LE showing support for "Toshiba Graphics Mode" which is really monochrome "Double CGA"...

http://www.toshiba-europe.com/computers/products/notebooks/t1000le/product.shtm
Click to expand...

Yes... before VGA became the norm, it was relatively common for high-end PC graphics systems to support 400-line video. That gave you a nice hi-res text mode, provided easy compatibility with CGA modes just by doubling the number of lines, and if there was enough video RAM, you got a full 640x400 graphics mode, too.
 
vwestlife said:
The cheaper CGA monitors just used ordinary TV-grade picture tubes, which is why they have the big dot pitch and usually no anti-glare coating. But if you think that's bad, try a Tandy VGM-225 VGA monitor with 0.52 mm dot pitch! I remember seeing one in the store and trying to view 640x480 VGA graphics on it was unbelievably fuzzy.
Click to expand...

The Toshiba TIMM got it beat with its 0.58mm dot pitch. Than again, its basically a TV with RGB input. Works great with 15.75khz sources though and blends the Apple IIgs 640x200 mode colors like the original Apple monitor. VGA is passable. Looks really good with ATSC OTA TV on 480p though.

For dedicated CGA, the Tandy CM-11 is one of the best. My NEC Multisync II does a good job, but like that Diamond Scan, it has very prominent scan lines. Some people like that look though.
 
njroadfan said:
The Toshiba TIMM got it beat with its 0.58mm dot pitch. Than again, its basically a TV with RGB input. Works great with 15.75khz sources though and blends the Apple IIgs 640x200 mode colors like the original Apple monitor. VGA is passable. Looks really good with ATSC OTA TV on 480p though.
Click to expand...

And anyone who's in SoCal right now can get one for cheap:

http://inlandempire.craigslist.org/ele/4551847304.html
 
njroadfan said:
The Toshiba TIMM got it beat with its 0.58mm dot pitch. Than again, its basically a TV with RGB input. Works great with 15.75khz sources though and blends the Apple IIgs 640x200 mode colors like the original Apple monitor. VGA is passable. Looks really good with ATSC OTA TV on 480p though.

For dedicated CGA, the Tandy CM-11 is one of the best. My NEC Multisync II does a good job, but like that Diamond Scan, it has very prominent scan lines. Some people like that look though.
Click to expand...

Ugh... the TIMM was terrible as a monitor.
 
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