VOGONS


First post, by VileR

User metadata
Rank Oldbie
Rank
Oldbie

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. 😁

web  /   blog   /   tube

Reply 1 of 13, by keropi

User metadata
Rank l33t++
Rank
l33t++

I have a PS1/pro mod. 2123 with some TI(? I think?) VGA onboard, would that work for your research?

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 2 of 13, by VileR

User metadata
Rank Oldbie
Rank
Oldbie

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 😀

web  /   blog   /   tube

Reply 3 of 13, by keropi

User metadata
Rank l33t++
Rank
l33t++

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?

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 4 of 13, by konc

User metadata
Rank Oldbie
Rank
Oldbie

...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
Filename
IBM PS1_6.jpg
File size
18.03 KiB
Views
618 views
File license
Fair use/fair dealing exception

Reply 5 of 13, by ripsaw8080

User metadata
Rank DOSBox Author
Rank
DOSBox Author

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? 😉

Reply 6 of 13, by Deksor

User metadata
Rank l33t
Rank
l33t
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

Reply 7 of 13, by orinoko

User metadata
Rank Member
Rank
Member

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 … ps1-2121s-svga/

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

ThetCTJm.jpg

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

YMaRh6Tm.jpg

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

2WXFMfcm.jpg

...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 🤣

Reply 8 of 13, by VileR

User metadata
Rank Oldbie
Rank
Oldbie

^ 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" 😉

web  /   blog   /   tube

Reply 9 of 13, by keropi

User metadata
Rank l33t++
Rank
l33t++

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

aDDo21El.jpg

fpejnPbl.jpg

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 10 of 13, by VileR

User metadata
Rank Oldbie
Rank
Oldbie

Excellent, thanks 😀 What screen is that- I assume the foreground is black and the background colors are the ones that change, yes?

web  /   blog   /   tube

Reply 11 of 13, by keropi

User metadata
Rank l33t++
Rank
l33t++

Just some chars made with TheDraw - colors like you described , it's the background that changes. I thought it was more clear like that.

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 12 of 13, by Great Hierophant

User metadata
Rank l33t
Rank
l33t

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 : 20150315_121234.jpg

Attachments

  • 20170220_162227.jpg
    Filename
    20170220_162227.jpg
    File size
    4.49 MiB
    Views
    473 views
    File license
    Fair use/fair dealing exception

http://nerdlypleasures.blogspot.com/ - Nerdly Pleasures - My Retro Gaming, Computing & Tech Blog