[HN Gopher] The VGA Attribute Controller Is Weird
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The VGA Attribute Controller Is Weird
Author : ingve
Score : 59 points
Date : 2024-05-05 07:45 UTC (1 days ago)
(HTM) web link (www.os2museum.com)
(TXT) w3m dump (www.os2museum.com)
| Koshkin wrote:
| Love these kinds of articles. (Now, I can only imagine how
| insanely more complex the modern hardware is!)
| kevingadd wrote:
| If you want something interesting on that topic, here's a
| fantastic explanation of one complex part of modern graphics
| hardware and how it varies across vendors
| https://www.gfxstrand.net/faith/blog/2022/08/descriptors-are...
| corysama wrote:
| Back in the day, Michael Abrash wrote quite a bit about how
| people would occasionally discover new video modes that VGA was
| capable of. Or, at lease some VGA controllers could support and
| others would crash the machine without warning.
|
| For Quake1 he wrote a little script language around each step of
| setting up the various modes. With that, it was much easier to
| navigate the maze of "Step A and C both failed, that means it's a
| Type 3 device and Step D will crash so, we should skip to the
| Branch 3 Path and hope for success at a lower resolution."
| hagbard_c wrote:
| > Back in the day, Michael Abrash wrote quite a bit about how
| people would occasionally discover new video modes that VGA was
| capable of
|
| That was not just true for VGA but for many of the
| ...interesting... cards which were put on the market 'back in
| the day'. I had one of those, a 'Diamond Brand' multi-IO +
| Hercules + memory card without documentation or drivers I
| happened upon at one of the then-ubiquitous hardware dump meets
| - it was the 'PC Dumpdag' in Amsterdam for those who remember
| that phenomenon - with which I spiced up my otherwise somewhat
| boring Bondwell BW 32. While working on a TSR (as in
| 'background routine') which would make it possible to automate
| data entry into some school management software package I ended
| up flipping a bit on the 6845 display controller on the thing
| upon which the vertical resolution suddenly doubled. Instead of
| 80 columns 25 lines it now displayed a somewhat compressed and
| initially messed up 80x50. Experimenting further I got it up to
| 80x70 and 132x70. I made another TSR to enable mode switching
| and used this quite a lot when working in Wordperfect and the
| like. It also did double the normal (720x348) graphics
| resolution which I got to work in a few programs but which was
| less useable than the text modes. I tested this program on many
| other boards but never found another one where it worked, alas.
| bombcar wrote:
| I remember trying every single SVGA driver that came on the
| SimCity 2000 CD until I found one that would let the game
| load; the board I had was some no-name knockoff, but the OAK
| TECHNOLOGIES driver worked.
| Zardoz84 wrote:
| I had the same issue! (but was Sim City 2000 on floppy
| disks). And I had a OAK SVGA card ... an OAK OTI 87 or 84,
| if I remember correctly.
|
| Also, I remember that with some tools that come on a floppy
| disk with the card, I could output a 1024x768 graphics
| scree, but with a horrible blinking... I think that I was
| putting my multi-sync monitor at the limit.
| livrem wrote:
| I thought of his Black Book when reading about the VGA
| registers. He goes quite deep into how the VGA hardware works.
| Interesting to read, but I only read it around 2010. Would have
| been much more useful to have read in 1990.
|
| https://github.com/jagregory/abrash-black-book
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(page generated 2024-05-06 23:00 UTC)