[Coco] 6309

[Gene Heskett]

On Sunday 07 October 2012 21:32:18 mike delyea did opine:

> I was just reading up on the 6309 and noticed that it can merge the D
> and W accumulators into a 64 bit Q accumulator.
> I'm familiar with using the A and B accumulators to make up the 16 bit
> D. Does the Q accumulator mean the 6309 can address 32 bit memory?

No, sadly its address register and interface is still only 16 bits wide, 
for 65535 bytes of main memory.  The Q is available for loads and stores, 
speeding those up marginally, but that is about it.  Not enough by itself 
to make it worth precision testing.

> That
> would mean 4gb of address space for memory (minus the OS ROMs).  Also,
> is it even practical for an 2mhz CPU to address that much memory
> assuming CAS/RAS?

Yes, but it is not the cpu doing the memory refresh, its the video chip 
doing that in between cycles when the bus is not otherwise occupied.

> 
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Cheers, Gene
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