Re: If you could design a $300 homecomputer today, what would you choose?

["william strutts" <wrstrutts1@nospam.home.com>]

"Byron Desnoyers Winmill" <wbdesnoy@acs5.acs.ucalgary.ca> wrote in message
news:9iuu8i$p9g$1@nserve1.acs.ucalgary.ca...
> william strutts (wrstrutts1@nospam.home.com) wrote:
> : > Hardware:
> : >  - 4MB to 8MB RAM
> <...>
> : >  - 64MB to 256MB RAM with battery backup, for
> : >    storing documents.  Or use flash memory if
> : >    it is cheap enough.
>
> : You couldn't get that much ram on a 68000 because it only
> : has a 24 bit memory bus.  You would have to go to a 68030
> : or so to get the wider data path.
>
> Then throw in some sort of decoder for the 64-256MB chunk.  Since
> it is not the main memory (that would be the 4MB chunk), it should
> not make much of a difference.  Indeed, it need not make any
> difference to the average programmer, since it would (presumably)
> be access through a set of file system calls.
>
> Besides, isn't the 6502 limited to 64kB chunks.  Apple simply
> implemented some sort of paging mechanism to access the 128kB found
> in later models (IIe/IIc).  Likewise for the 192kB card which I
> have lying around here, somewhere.  (Though my understanding is
> the 1MB card for the 8-bit machines used some sort of window into
> memory.)
>

Memory Management Unit which really extends the addressing
the processor has.  To the programmer, it is as if you had 32 bit
addressing.  You set the MMU chip to "bank" of RAM you
want and pass the rest of the address to memory bus.  However,
you would then need to develop a MMU and the added cost
of R&D would increase your cost to build.  It would be safer
to just move to a 68020 or 68030 processor and bypass the
smaller bus.  I would think the chips are not much different
in cost these days as they have been around a long time.

--
--
William R. Strutts - wrstrutts1@nospam.home.com - Whatever!

C'est moi!  http://www.facelink.com/wrstrutts

Just hacking away...

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