On Friday, December 13, 2013 01:23:15 pm Ted Unangst wrote:
> On Fri, Dec 13, 2013 at 12:33, Jeff Simmons wrote:
> > "Nobody will ever need more than 640k RAM!" -- Bill Gates, 1981
>
> I realize this is often quoted in jest, but I've taken to setting the
> record straight because I think the truth is more interesting than the
> lie. People who don't know the real history are doomed to repeat it
> without even realizing it.
>
> The 8088 CPU in the original PC, which was designed and built by IBM
> before MS was involved, had a 20 bit physical address space. That's
> one megabyte. So the most RAM the PC ever could have supported was
> 1MB, not so very much more than 640KB. But then out of that 1MB you
> have to carve out some space for things like the BIOS and the video card
> (and sound card, and network, and ISA whatever). So the engineers at
> IBM said that the top 384K of the address space would be wired up to
> peripherals instead of RAM, leaving 640K. It's a hardware limitation,
> not one of software. OpenBSD doesn't use that 384K either.
>
> And it's not a limitation that only happened once. If you stick 4GB of
> RAM into your PC and boot OpenBSD i386, you'll see that you only get
> about 3GB. Basically the same thing. Space has been reserved for
> peripherals, so you don't get to use the RAM in that space. If you
> boot amd64, you'll get to use it because the memory is remapped higher
> up, above 4GB. (And if you bought a 80386 and booted 32-bit Windows,
> you got to use the memory above 640K too).
>
> Nobody ever proclaims "3GB of RAM will be enough for everybody!"
> -- random dude at Intel, but that's exactly what happened. The same
> "mistake" was repeated. And then came the various workarounds like
> PAE, just like there were workarounds like expanded memory in the DOS
> days. For that matter, nobody ever says "80 bytes of memory will be
> enough for everybody!" -- John Mauchly (ENIAC)
>
> There's a lesson in there about foreseeing future requirements, but
> there's also a lesson that should be learned about real world products
> being subject to real world constraints. You go to market with the CPU
> architecture you have, not the CPU architecture you want. I'm reminded
> of Bjarne Stroustrup's comment about there being languages people like
> and languages people use.
>
> Sorry to spoil the fun.
Not at all. Once upon a time, I made a lot of money using memory managers to
cram stuff into that 384k, especially Novell Netware drivers. And I cut my
teeth hacking PDPs in the early 1970s, so I'm fairly familiar with memory
limits in early machines.
And I still (especially given the context in which Mr. Gates said it) think
it's funny.
--
Jeff Simmons jsimm...@goblin.punk.net
Simmons Consulting - Network Engineering, Administration, Security
"You guys, I don't hear any noise. Are you sure you're doing it right?"
-- My Life With The Thrill Kill Kult
