Re: Peek/Poke Low-Level parallel-port/memory/video-buffer/keyboard-buffer?
- From: nem <nem@nospam>
- Date: Sat, 22 Nov 2008 16:47:32 -0600
Marc 'BlackJack' Rintsch <bj_666@xxxxxxx> wrote in news:
Not really and it's not a matter of the chosen programming language.
PCs usually don't use memory mapped IO, so there is a difference
between accessing memory and hardware registers. The "screen buffer"
isn't in main memory but in many cases in memory on the graphics card.
PCs use port-based I/O, an antiquated concept that seemed like a good idea
in the '70s. Regarding video memory, PC video cards traditionally had their
own RAM which mapped into the CPU's address space. Modern PCs have an
onboard video system that simply takes some of the system RAM for itself.
3D accelerator cards meanwhile have separate RAM.
The ability to POKE into any part of the memory would be a bad thing.
The operating system is not in ROM anymore. If it is not protected,
any software could accidentally crash the whole system or even worse,
any virus can plant code into the core of the operating system. Ouch.
Another difference is that modern PCs do not use the BIOS for much of
anything except the boot phase. Windows has it's own drivers for everything
right down to the keyboard. That's because the BIOS resides in the first
megabyte of memory, and cannot be accessed without switching out of
protected mode.
In most cases, Windows has severe restrictions on what ports and memory
areas an application can access. Windows 95/98 were less stringent about
this than NT, which was why the latter could not run many games, although
that changed with XP.
Nope, PCs nowadays aren't like the simple little world of 8-bit machines
where you could do anything you wanted.
.
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