Re: Re: A86: Questions on Port 3, calc on, off, APD, etc
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Re: Re: A86: Questions on Port 3, calc on, off, APD, etc
>It is not how the 16-bit segment and 16-bit offsets overlap that form the
>1meg barrier. All 4 gigs of memory on a pc can be accessed with a 386 or
>greater in protected mode by simply using a 32-bit pointer. The 1 meg
>limit comes from the 8088/8086 having only 20 address lines for memory.
>2^20 = 1 meg. The 286 had 24 address lines, and it can address 16 megs of
>memory in pmode. 2^24 = 16 megs. And the 386 and later have 32 address
>lines, hence the 4 gigs of ram. Not that many (if any) people have that
>much ram on a pc, but 16 megs on a 286 is like 4 gigs on a PII, believe it
>or not!
Ahh I remember! The 286 introducted protected mode programming, well the 386
introduced it mainly though, I remember now. Yeah the dos extenders like in
Quake and Doom used protected mode and DJGPP does too, ehh? Yeah my friend
is a hardware guy (builds computers) but couldn't believe that a 386 could
theorically access up to 4 gigs of memory. I tell him that you learn the
most about computer hardware if you are a programmer and that the only
memory restrictions on a computer are the maximum memory addressable by a
CPU.. Then I tell him his calculator (HP 3 something) is an 8-bit processor
that
can only access up to 64K. But he is like "yeah but you can buy expansion
cards for up to 4 megs"... then I had to explain memory page swapping..
I have been to three high schools and met no one who could program even C
let alone assembler. Which sucks... what do you talk about during Lunch? The
tornado that took our gym room or the serial rapist on campus??.. Nah that
gets old too quickly.. Stephen Hicks lives in Tampa Florida and I live in
Clearwater, I was kind of amazed he is only a half-an-hour drive away from
me. That doesn't happen very often when you talk to somebody over the
internet that they live "relatively" close to you
>Now, back to z80 on the calc--where the fun is!
Amen