Comments by "MrAbrazildo" (@MrAbrazildo) on "The Truth About The Fast Inverse Square on N64 | Prime Reacts" video.
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7:08, in old hardware, the engine instructions/data didn't fit entirely on the cache. So, depending on how many instructions an action takes, CPU had to seek the RAM, which uses to be 100x slower (maybe less in a console). On modern hardware, all instructions/data are in the cache, which has much more memory than they require, for an old game. However, RAM is still used even nowadays, for multimedia stuff: images, video, audio, textures and other more than 64 KB sized. The optimization for these large things targets to load part of the RAM on the VRAM (GPU cache memory), in a moment the user doesn't care, like a loading scene - i.e. God of War's Kratos passing through some rocks. Sometimes this is used for loading from files to RAM too.
11:58, but he is doing it for modern hardware, isn't he? The video's goal is just to explain why Quake's alg. is not meant for all cases.
13:00, the sad truth is that these pointer transformations are UB (undefined behavour). That's why the guy commented it as "evil": he just wanted to get his job done, leaving the comment for the future masochist who will deal with the potential nasty bug. UB means the operation is not standardized. So, the app may someday start crashing or giving wrong values (out of nowhere!), if any thing change from the original setup: hardware, OS, any imaginable protocol that interacts to the game. Not even old C had an expected action for that, as long as I heard.
13:52, in math, a minus exponent means that the number is divided. So, x*0.5 == x / 2 == x*2^(-1). Instead of multiplying the whole number, it's possible to change its exponent, by sum or subtraction, which are faster operations.
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