[Coco] What would a CoCo successor have to have as a minimum?

[Little John]

There are two sets of task registers, 8 bytes each with the TR bit 
determining which of the two is active :-)
I can provide you with all of the design details. I doubt that I would ever 
get around to building it - but I may one day - it would require way too 
many 30 pin simms, so I'm having to design with 72 pin simms which could 
theoretically max it out with 4 modules of 128MB. I was going to stick the 
whole thing in a Xilinx CPLD...
-John also ;)
----- Original Message ----- 
From: "John Kent" <jekent at optusnet.com.au>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Saturday, November 20, 2010 8:53 PM
Subject: Re: [Coco] What would a CoCo successor have to have as a minimum?


> Hi Little John,
>
> That sounds very good !
> If the pages are 8K then shouldn't you only need an 8 byte register file ? 
> ( 8 x 8K = 64K)
>
> John
>
> On 21/11/2010 7:23 AM, Little John wrote:
>> What my son and I have done as far as extending CoCo 3 memory was to map 
>> register files (or dual port SRAM) at $FF80-$FF8F. These serve to extend 
>> the MMU to 16-bits. For example, $FFA0 = LSB,$FF80=MSB and so on.This 
>> extends the coco 3's RAM capacity to 512M or 65536 8K blocks, while 
>> remaining compatible with existing software. Using the Video Bank 
>> Register (the one designed by disto to bank the memory as 512K banks for 
>> the GIME's video circuit) allows 256 512K video banks. So the video can 
>> be placed in any 512K bank within the first 128Meg. The CPU can access 
>> the entire 512M as 8K pages. Although the design is complete, it has yet 
>> to be prototyped and tested.
>> -JohnT-
>> ======
>>
>>
>>> There is flash memory on the DE1 board and there is 8MBytes of SDRAM 
>>> which to the best of my knowledge is not used.
>>> Access to extended memory can easily be achieved by mapping in another 8 
>>> bit page register in I/O somewhere to extend the memory.
>>> This would remain backwards compatible with the CoCo3 as the register 
>>> would not need to be modified for existing programs.
>>>
>>
>>
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>
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