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movq
www.uninformativ.de
 (2y ago)

Today’s Advent of Code puzzle was rather easy (luckily), so I spent the day doing two other things:

  • Explore VGA a bit: How to draw pixels on DOS all by yourself without a library in graphics mode 12h?
  • Explose XMS a bit: How can I use more than 640 kB / 1 MB on DOS?

Both are … quite awkward. 😬 For VGA, I’ll stick to using the Borland Graphics Interface for now. Mode 13h is great, all pixels are directly addressable – but it’s only 320x200. Mode 12h (640 x 480 with 16 colors) is pretty horrible to use with all the planes and what not.

As per this spec, I’ve written a small XMS example that uses 32 MB of memory:

https://movq.de/v/9ed329b401/xms.c

It works, but it appears the only way to make use of this memory is to copy data back and forth between conventional memory and extended memory. I don’t know how useful that is going to be. 🤔 But at least I know how it works now.

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xuu
txt.sour.is
 (2y ago)
↳ In-reply-to » Today’s AoC puzzle is a very simple problem on modern machines, but quite tricky for me: It involves a number that doesn’t fit into 32 bits. 🤔 I wonder if/how I can manage to port this beast to DOS. (I once wrote a “big int” library myself, but that was ages ago and I hardly remember it anymore.)

@movq@www.uninformativ.de it shouldn’t need a full bignum implementation right? Just some left and right shifts for the sq/sqrt and carry for the addition right?

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xuu
txt.sour.is
 (2y ago)
↳ In-reply-to » … it just finished and brute-force worked. 18 minutes of computing time on my 11 year old machine, single-threaded.

@movq@www.uninformativ.de It took a little over a minute on my machine.. i should try to make it multi threaded.. 🤔

Executed in   68.96 secs    fish           external
   usr time   60.84 secs  242.00 micros   60.84 secs
   sys time   12.52 secs  252.00 micros   12.52 secs

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xuu
txt.sour.is
 (2y ago)
↳ In-reply-to » It is a pleasure to work with the help system of Borland’s Turbo C++ 3.0 on DOS. The descriptions are clear and concise. There are short and simple examples. Pretty much every help page is cross-refenced and those links can be clicked.

@eapl.me@eapl.me I have many fond memories of Turbo pascal and Turbo C(++). They really did have a great help system. And debug tools! Its rare for language docs to be as approachable. QBasic was great. As was PHP docs when I first came into web.

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