[Coco] CoCo3 MMU Register question...

[L. Curtis Boyle]

From what I remember, for 128/512K Coco 3, it always used the highest 8 banks (56-63), and 128k ghosted them 4 times. I don’t remember what 1 and 2MB versions did.


> On Mar 30, 2015, at 12:53 PM, Zippster <zippster278 at gmail.com> wrote:
> 
> I have a scheme in mind, using a CPLD for address decoding, and high speed latches
> for the MMU bank registers, that would operate similarly to one set of CoCo3 MMU banks.
> 
> With 8 banks (0-7), the same register locations in memory as the first instance in the CoCo3 (TR 0).
> Using each memory location ($FFA0 - $FFA7) to hold an 8-bit value for the memory block to map to (in a latch).
> 
> Perhaps someone who knows about OS9 can tell me if a simplified MMU scheme like this would be
> suitable to compile OS9 to use.  This is without a second task register, and no ability to read the MMU registers.
> Those things could be implemented if necessary, but trying to keep it simple.
> 
> Any thoughts or suggestions?  Unfortunately I don’t know squat about OS9’s memory usage.
> 
> - Ed
> 
> 
>> On Mar 30, 2015, at 1:22 PM, Joe Grubbs <jsgrubbs at hotmail.com> wrote:
>> 
>> I wish I could help because this sounds like a great project, but I don't know enough about my Coco3 to get this information.
>> 
>> 
>> 
>> --- Original Message ---
>> 
>> From: "Zippster" <zippster278 at gmail.com>
>> Sent: March 30, 2015 9:03 AM
>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>> Subject: [Coco] CoCo3 MMU Register question...
>> 
>> Hi guys,
>> 
>> Can anyone tell me what the default state (on power-up) is as far as the
>> values in the MMU registers in the CoCo3?
>> 
>> Any information on how they are initialized/configured on startup would be appreciated.
>> 
>> Working on a 2meg RAM upgrade for the CoCo2, and I want it to mimic CoCo3 RAM handling
>> as closely as possible.
>> 
>> Thanks,
>> 
>> - Ed
> 
> 
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