[Coco] How much memory

[Frank Pittel]

On Sun, Nov 28, 2010 at 08:51:53PM -0500, Aaron Wolfe wrote:

> 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

> application.

> 

> 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).


That's only the case if the fpga "6809" is limited to a 16 bit address bus. :-)

The Other Frank