Blinkenlights: PC Binary Emulating Visualizer

Back in the day memory was very limited. CPU was slow too, but I'd even say memory was the main limitation. So, programs, and games in particular, used every single byte of the RAM. This of course left the crackers, who wanted to add their intros to the games, with a problem.

The solution was to compress the game to make room for the intro. After decompression it would still fill the available RAM 100%, so where to put the decompressor? You'd put it and ran it in the video RAM, which wasn't needed during decompression. It would be overwritten when the game started, but then the decompressor wasn't needed anymore. The only side effect was that you literally could see the decompressor run on your screen.

If you ran a game such as Marble Madness, rebooted the machine, then started the viewer program, very frequently you'd find corrupted remnants of the game assets such as sprites and backdrops as you scrolled.

I was young and absolutely amazed by it. Unfortunately I can't remember the name, only that it came on a disk with 'The Alliance Anti-Virus Collection' hand-written on the label. It had many other cool utilities, some which hijacked the "Insert Workbench" screen to play chiptunes and display scrolling text

Bitter-sweet memories.

Here's another example how memory visualization is useful, this time in an 8-bit home computer emulator (where such things are very trivial to do in realtime, because the performance difference between an 80's home computer and a modern machine is so big).

You can see how a visual effect in a scene demo works by looking at the memory access "heat map":

https://twitter.com/FlohOfWoe/status/1075083521193062401

I also found the "execution heatmap" very useful for debugging, this just "paints the map" where the instruction pointer is reading memory, with the current location extra highlighted. One can understand a lot of things about a given program by just watching execution jump around in memory (such as, where are the "hot loops" versus what is one-time code, what memory regions are code, and what are data, etc...

(edit: replaced the link with a better example)

I wish there were more things like this out there that showed something at least SLIGHTLY useful versus the obligatory "matrix rain" everyone uses to show off their terminals on /unixporn

I started programming in BASIC and it was interesting but I felt I was missing a lot in my understanding of what was really going on.

At some point I found a program called "picoprocessor" that was along these lines, but vastly simpler of course. It created on the display an operator panel for a 4-bit computer, it had maybe 2 registers and only a few operations but it was enough to get the light bulb glowing in my head about how computers worked at the assembly language/machine code level.

Seeing the state changes visually on the "panel" as the program ran was so helpful to my understanding that I still remember the experience quite clearly some 40 years later.

My dad also commented about the computers in the lab where he worked, that had operator panels with toggle switches and LEDs. He could tell what loop the program was running by the pattern of lights on the panel.

  > "Watching this program execute (c / ctrl-c) at adjustable speed (ctrl-t / alt-t) it becomes clearer that the process of printing an image is basically a pipeline that goes: IDCT → Y′CbCr to RGB → decimate → sharpen → block render. Thanks to Blinkenlights we can also see that the RGB conversion is going slower than it should, because code isn't benefiting from SSE register vectorization. Many other common issues concerning micro-optimization, such as register spillage, become super apparent as well."

https://help.typefi.com/hc/en-us/articles/360000762936-Get-s...

If I recall correctly, the command was: "Telnet towel.blinkenlights.nl"

I wonder if its still active.