[Coco] 2MB Memory Upgrade For The Coco 3

[Gene Heskett]

On Sunday 05 August 2012 13:40:23 Stephen H. Fischer did opine:

> Hi,
> 
> Tony's "DISTO 2 Meg Upgrade" manual and the "inside the 2 Meg Upgrade"
> book with schematics are on the web (Suggested that it is flawed
> intentionally) .
> 
> PM me for links if you are interested, we are not posting links even on
> the list to try and keep the traffic down for the site.
> 
> Getting parts may be hard if you wish to build your own.
> 
> The inside book is useful for understanding how the 2 Meg Memory
> upgrades work.
> 
> SHF
> 
My advice is that the book is far more useful in that it would let a savvy 
board(s) designer build his own with the devices he happens to have in the 
spares box.  I say that precisely because the 1 megabyte simms that kit 
used are, in the year 2012, made from 99.99% pure un-obtainium.  One must 
bear in mind that the refresh counters needed for more modern memory will 
often need expanded 2 to 8 bits beyond the measly 7 or 8 the coco supplied, 
and that is at least as challenging a design project as the extra memory 
registers etc it takes to make a full 2 meg memory map, in 8kb pages.  
Memory with that width of refresh will also carry a longer time till 
refresh needed as it was forced to become less leaky in order to hold its 
data well till the next refresh cycle came around.

Cheers, Gene
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