Back in my day, when we saw something in RAM that we liked, we just read it.

My BBC Micro (6502) even had a memory viewer in ROM that ran at ~50fps and I remember the fun looking at running timers and keyboard/joystick ports getting activated and such.

Years ago I wanted to do that on windows and found out that there was something called protected memory, now it finally looks like I can experience that fun again, although at a slower pace it seams ;-)

Which also meant you could do a lot of optimisations - like moving the stack pointer to point to the display memory area and using 'push' to blit a chunk of image data to screen which was quicker than using an 'ld' loop.

Also having polymorphic functions where you could write over a couple of bytes to make the function behave differently at runtime - saving code memory space - and learning the hex for most of the common opcodes at same time.

You can still do that, even more so on systems with memory protection as you will not break OS's interrupt handlers by doing that.

Notably pixomatic (Rad Game Tools' SW rasterizer) compiles Direcd3D shaders into i386 code which uses ESP as general purpose register.