A small request for IBM PS/1 or (VGA) PS/2 owners

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A small request for IBM PS/1 or (VGA) PS/2 owners

Postby VileRancour » 2017-2-18 @ 22:35

The VGA-compatible text mode Wikipedia article has some information which looks false to me. Basically, it states that the shaded block characters (0xB0-0xB2, ░▒▓) should have their last pixel columns doubled in 9x16 text mode, rather than blank.

This is quite at odds with every VGA card I've ever seen, where repeating those characters *does* visibly show blank columns between the character cells. On the other hand, I don't think I've seen a real IBM VGA in action -- if we had visual proof of how the original specification actually behaves, that'd put it to rest.

So, if you own an IBM PS/1, or PS/2 (VGA-based, not MCGA), or an ISA IBM VGA card, I'd like to request a photo of your monitor showing this in action. For example, one of these images:

- This screen from FreeDOS EDIT (choose Utilities -> ASCII table)
- The loading screen from Commander Keen 4
- Anything else that extensively uses the shaded block characters.

Yep, I realize that there's little point in sperging over details like this, but someone just emailed me regarding the VGA fonts on my website, and pointed me to the Wiki article (suggesting that my fonts may be following faulty documentation). So I thank you in advance for helping me settle the matter, and fighting the good fight against Wikipedia revisionism. :D
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby keropi » 2017-2-18 @ 22:37

I have a PS1/pro mod. 2123 with some TI(? I think?) VGA onboard, would that work for your research?
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby VileRancour » 2017-2-18 @ 23:02

Oh - didn't realize that IBM themselves used third-party VGA chips on some models... an original IBM part would be preferrable I guess. Thanks though :)
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby keropi » 2017-2-18 @ 23:25

Maybe TI built it for IBM? I don't exactly remember, I'll have to take a good pic I guess.
What is the chip of an IBM vga? does it have the IBM logo or something?
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby konc » 2017-2-18 @ 23:55

...and I have a 386SX PS/1 type 2133 with some on-board VGA, I really can't recall what it is. Please let me know if you want me to look it up.

IBM PS1_6.jpg
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby ripsaw8080 » 2017-2-19 @ 01:21

VGA-compatible video cards duplicate the 8th dot to the 9th when the upper 3 bits of the character number are 110 ((char & 0xE0) == 0xC0), in other words chars 0xC0 through 0xDF. Besides, who isn't used to seeing the "pinstripes" on a screen filled with the checkerboard block? ;)
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby Deksor » 2017-2-19 @ 07:20

konc wrote:...and I have a 386SX PS/1 type 2133 with some on-board VGA, I really can't recall what it is. Please let me know if you want me to look it up.

IBM PS1_6.jpg


I've got the exact same but in black color. IIRC it's an onboard cirrus logic
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby orinoko » 2017-2-19 @ 12:13

Just set up my IBM PS/2 Model 40SX. It has what appears to be a TI made VGA controller, as mentioned here https://ps1stuff.wordpress.com/2016/09/13/the-mistery-of-the-ps1-2121s-svga/

I created a small qbasic program to output chars 176,177 and 178 with color 0,15 set:

Image

Figuring this doesn't tell the full story, I changed it to color 15,9:

Image

Having said this, I much prefer to use this Diamond Stealth Pro (based on the S3 86C928 chipset):

Image

...which seems to show exactly the same output as above, but unlike the inbuilt TI VGA chipset, this S3 card doesn't have the Keen scroll bug :lol:
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby VileRancour » 2017-2-19 @ 23:38

^ That's exactly the type of photo I was after, thank you.

I suppose the question now becomes which specific chips are used on the earliest IBM VGA systems - that is the original PS/2 models 50/60/80, or the original IBM ISA VGA card (IBM Personal System/2 Display Adapter, P/N 1887744). Actually, here's the model 70 board.. can you spot the VGA chip?
If we can get a screen photo off of that one, that'd be the ultimate piece of evidence. I'm personally 99.99999% sure it'll show the exact same behavior, but why not go for flawless victory ;)

ripsaw8080 wrote:VGA-compatible video cards duplicate the 8th dot to the 9th when the upper 3 bits of the character number are 110 ((char & 0xE0) == 0xC0), in other words chars 0xC0 through 0xDF.

...which is more plausible than Wikipedia's claimed 0xB0-0xDF range -- in terms of logic design, checking for that one would be quite a bit more complex.
I guess that further support comes from how the character set itself is mapped. The 0xB0-0xBF range contains some box-drawing chars, but none of them join to the right - right-joining chars need their 8th dot column duplicated, and they're all mapped to 0xC0-0xDF. (And of course, the character set dates back to the original IBM PC, whose mono adapter also originated the 9th-column duplication logic.)

Besides, who isn't used to seeing the "pinstripes" on a screen filled with the checkerboard block? ;)

Wikipedians who go to spurious Intel documentation instead of using their own eyes, because the former is a "notable source" while the latter is "original research" ;)
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby keropi » 2017-2-20 @ 08:20

here is mine, most likely the same TI controller made for IBM:

Image

Image
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby VileRancour » 2017-2-20 @ 16:12

Excellent, thanks :) What screen is that- I assume the foreground is black and the background colors are the ones that change, yes?
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby keropi » 2017-2-20 @ 16:19

Just some chars made with TheDraw - colors like you described , it's the background that changes. I thought it was more clear like that.
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby Great Hierophant » 2017-2-20 @ 22:16

VileRancour requested that I take a photo of my screen showing the output from my IBM PS/2 Display Adapter, the original IBM 8-bit VGA card. I have attached a photo clearly showing that there is a blank column of pixels for the ASCII characters B0, B1 & B2, just like almost every other VGA card.

This is the card I used : Image
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20170220_162227.jpg
http://nerdlypleasures.blogspot.com/ - Nerdly Pleasures - My Retro Gaming, Computing & Tech Blog
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Re: A small request for IBM PS/1 or (VGA) PS/2 owners

Postby VileRancour » 2017-2-20 @ 22:37

Man, that was quick - excellent, you rock. :) Much obliged!
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