[Coco] CoCo2 RAM upgrade idea questions

[Edward Snider]

Thanks David, I will check that out.

- Ed
On Jan 23, 2015 10:08 PM, "David Linsley" <davidlinsley at gmail.com> wrote:

> There was a post about the Dragon mod to add 256k and patch L2, a few
> months ago. I've copied it below:
>
> From: Ken H. <dragon.atv at gmail.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Sun, Nov 30, 2014 2:24 pm
> Subject: Re: [Coco] Design files for 512k or more CoCo3 upgrade
>
>
> There was a 256k upgrade for the Dragon / CoCo2 which was published back in
> 1989 by Bob Hall in the Dragon Update newsletter.
>
> It's based on 256K with 8k pages, just like the CoCo3, which allowed to run
> Tandy OS9 Level 2. That makes it much more useful than the banker board.
>
> Here is the series of articles which include the schematics and OS9 patches
> (the final 256k design is at the end):
> https://drive.google.com/file/d/0B9wgnqGFDmhka2JLS1hrUDhJVEU
>
> Ken
>
>
> -----Original Message-----
> From: "Gene Heskett" <gheskett at wdtv.com>
> Sent: ‎1/‎23/‎2015 6:00 PM
> To: "coco at maltedmedia.com" <coco at maltedmedia.com>
> Subject: Re: [Coco] CoCo2 RAM upgrade idea questions
>
> On Friday 23 January 2015 20:01:15 Allen Huffman did opine
> And Gene did reply:
> > > On Jan 23, 2015, at 6:12 PM, Zippster <zippster278 at gmail.com> wrote:
> > >
> > > What size RAM bank would be best to swap in and out the 64k
> > > addressing space from the extended memory?
> >
> > The CoCo 3 swaps out 8K blocks. If that were doable, perhaps porting
> > OS-9 L2 to the CoCo 1/2 would be possible. Interesting.
> >
> > > From the programming (OS9) point of view, what is the preferred
> > > method of handling the bank switching?  And how has it been handled
> > > in the past with ram upgrades on the CoCo1/2?
> >
> > I never knew anyone with an upgraded CoCo, but I recall ads in Rainbow
> > advertising upgrades "up to 8mb" back then. Wild.
> >
> > > What would be the best amount of total memory?  2mb?
> >
> > Does anyone even make >512MB upgrades for the CoCo 3 these days?
> >
> Not that I am aware of.  I have a 2 meg disto kit though, works very well
> indeed.  The problem is in designing the addressing latches to add the
> last 3 bits to the gime mapping, doing it in parallel with the gime's own
> logic, with minimum timing skew between the gime bits output and the added
> 3 bits so as not to confuse the memory.  Tony may even have used the same
> buffering scheme for both sets of bits so that it all switched fast enough
> not to screw up the memories latching skew.  I have schematics, but I'll
> guarantee they are wrong, Tony never published anything that was
> absolutely accurate.  He treated his schematics that went out like a
> cartographer does his artwork.  Copyrighted mistakes. :)
>
> > > What would be the best version of OS9/NitrOS9 to run on a CoCo1/2
> > > with extended memory? Level 2?  Level one is for just 64k systems?
> >
> > Level 1 wanted a flat memory map. The modern OS-9/68K/PPC/etc. is Level
> > 1, using the MMU only for memory protection (if the system has it).
> > Level 2 was the one that used an MMU to remap memory.
> >
> > I wish I could remember more.
>
> So do I, I was asked when I went to the garage to work on that chest for
> an hour or two after dinner, to please turn off the air compressor before
> I came in, so of course I forgot it, and just caught a bit of static from
> the LW. Short term memory loss at 80 yo is a real problem folks. :(
>
> >               -- A
>
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page <http://geneslinuxbox.net:6309/gene>
> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
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