What was that mystic Commodore 6509 computer?

From: tim lindner <tlindner_at_ix.netcom.com>
Date: Sun Jun 2 10:06:21 2002

> Cameron Kaiser wrote:
>
> > On the 6509, there are four extra address lines, giving you up to 1MB.
> > These lines are set by location $0000 for execution (which 64K "bank" the
> > code is running from) and by location $0001 for indirection (i.e., on
> > indirect indexed LDAs and STAs *only* the four bits in $01 would be
> > asserted on the address lines to get at another bank). Not quite segment
> > and offset addressing. :-)
>
> And the 8086 segment addressing is a improvement?
> The only clean 8 bit extended addressing was with the 6809 and OS/9 level
> Two. Here you had 16 pages ( 4kb-each ) of virtual memory ,if I remember
> right, per processes with the upper 256 bytes common memory.

Actually it was 64 8k banks (512k total). Any 8 banks could be mapped
into the 64k address space.

I wouldn't call it virtual memory because that usually refers to RAM
with a backing store file (usually on a hard disk).

-- 
tim lindner                    tlindner_at_ix.netcom.com
"Life. Don't talk to me about life." - Marvin, the android
Received on Sun Jun 02 2002 - 10:06:21 BST

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