Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!portal!cup.portal.com!FelineGrace
From: FelineGrace@cup.portal.com (Dana B Bourgeois)
Newsgroups: comp.sys.amiga.tech
Subject: Re: maximum memory
Message-ID: <24049@cup.portal.com>
Date: 14 Nov 89 10:21:12 GMT
References: <3157@ccncsu.ColoState.EDU>
Distribution: na
Organization: The Portal System (TM)
Lines: 29

[line eater food]

Commodore/Amiga chopped up the 16 Meg space by allocating some for
chip ram, some for ROM(WCS), some for hardware expansion(registers
and ROM), and some for expansion RAM(fast RAM) and some space for
later use(reserved).  Turns out that the bottom 1 Meg is chip, there
is a meg reserved, the WCS and hardware take up another couple of megs 
or so and half of the 16 Meg address space is fast ram.

Coming from an 8 bit machine, or an MS-DOS machine or even a small
(medium-sized?) minicomputer, 9 Megabytes of memory must have seemed
like plenty of address space.  In 1984 that would've been 16x8x9 DRAMs
at $5 each or 1152 chips costing about $5500!!  By 1985 you could get
256K DRAMs so the number of chips is down to about 250 but the cost is 
still over $5000.  It isn't until 1986 that the price of 256K DRAMs
would lower the price of 9 Megabytes to say $3000.  I'd say that the
designers were far seeing indeed to have left over half of the available
address space when they could've said,

"Who'll ever need more than 2 or 3 megabytes?"

The 32 bit machines will probably result in more fast ram beyond the 16 
megabyte limit of 24 address bits.  THere is lots of room in the map
for hardware expansion and my guess is that the architecture will be
redesigned before the memory map becomes outdated.

One area where the mistakes of MS-DOS weren't repeated.

Dana @ cup.portal.com