[Coco] How much memory

Aaron Wolfe aawolfe at gmail.com
Sun Nov 28 20:51:53 EST 2010

On Sun, Nov 28, 2010 at 9:04 PM, Frank Pittel <fwp at deepthought.com> wrote:
> On Sun, Nov 28, 2010 at 05:51:45PM -0500, RJRTTY at aol.com wrote:
>> In a message dated 11/28/2010 5:35:23 P.M. Eastern Standard Time,
>> cmayeux at msbministries.org writes:
>> >Perhaps we could keep it at 2 megs to eliminate some  hardware
>> >And software "backpedaling"... just a thought.
>> I agree.   2 megs is plenty of memory for an 8 bit 2 mhz
>> processor to run around in.....
>> and it has a certain symmetry to it since the task registers
>> will also be 8 bits in a 2 meg system...
> The coco3fpga can run the "6809" as a 25mhz cpu and doesn't have the limitation
> of only being able to directly address 64K or memory!

The 6809 can only directly access 64k of memory whether it's in
silicon, FPGA, or being emulated accurately.  This is a fundamental
aspect of the chip, it is true of all 6809s everywhere in every

The CoCo allows you to use more than 64k by mapping in little pieces
of a larger address space into the single 64k space the 6809 can
actually talk to.  Giving it massive amounts of RAM doesn't change the
fact that at no time will the 6809 ever seen more than 64k of it.
This is not a function of an operating system or programming, it is
simply how a 6809 works (and also how many other "8 bit" chips which
had 16 bit addressing work).

> The Other Frank
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