Re: Multithreading OS for the C64

[fachat@physik.tu-chemnitz.de (Andre Fachat)]

Bruce R. McFarling (ecbm@cc.newcastle.edu.au) wrote:
: 	Notice that normally the 6502 address space is full
: with additional memory (if available) banked in by an external
: memory management arrangement.  So if the 6502 *had* 'boundary
: errors' it would be pointless -- I believe the Andre's original
: 6502 box had memory banking on 4K boundaries (is that right?)
Yes you are right. The upper 4 address bits were taken as index
into 16 registers each 8 bit wide. So I had 16 chunks of memory,
each 4kByte in size.
These could then be mapped to any of 256 chunks within the 
extended up to 1MByte memory.

: which give 16 different relocatable chunks of memory in the
: memory space.  So the assumption that
: 	(logical address space) > (physical address space)
: is often strictly false for a 6502 machine. (That includes
: the original 6502, with 64K RAM, 16K ROM, and 0K < IO < 4K
You mean C64, don't you?

Andre


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