>"640K ought to be enough for anybody." -- Bill Gates, 1981.
>
>how does this relate to today's RAM, such as 64MB?
>
>is it a factor of 100 or 1000 or ????
>
>and he /was/ referrring to RAM, right??
hope this gets across the wire before you need to leave for the talk (and
break a leg, BTW)..
the 640K issue deals with a trick the early x86 microprocessors used to
manage memory. processors use binary addresses to identify locations in
memory, so the amount of memory visible to the processor is directly
related to the size of the addresses it can generate. the size of an
address is restricted by the number of physical circuits on the chip
dedicated to handling that job.
therefore, the bigger your effective address space, the more microacreage
you have to burn for address handling circuitry. that costs money,
increases the complexity of the chip, and breeds other (expensive) changes
in the electronics of the motherboard.
Intel's way of dealing with the problem was to use a mid-sized (at the
time) address space, with enough circuitry to handle 64K of distinct
addresses, which became known as a 'page'. then it added another batch of
(smaller, cheaper) circuitry that allowed the chip to hop from page to
page, giving the effect of a much larger address space than it actually had.
the problem was that hopping from one page to another was slow & clunky,
and spreading the data for a single program across multiple pages causes
all sorts of problems. the more pages you have to keep track of, the
worse the problems get. a program which used 640K all at once would be a
hideous, unruly monster.
just goes to show that Bill hadn't realized his own potential back in '81. ;-)
mike stone <[EMAIL PROTECTED]> 'net geek..
been there, done that, have network, will travel.
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