[Coco] RAM expansion options for the CoCo 3

[L. Curtis Boyle]

A light correction on the use of 128K - If you use the Coco 3 mode graphics, those are all outside of the 32K of “normal” BASIC RAM. The screens themselves take up to 30K, and the HGET/HPUT buffers come out of that extra RAM as well - so a large BASIC program running in the highest Coco 3 graphics modes, using get/put buffers, can easily take more than 64K.

Re: 1MB and 2MB RAM upgrade under OS-9 - the patches were very small (and are all built into NitrOS-9, so you don’t need patches at all for that) - basically just to allow 128 or 256 MMU blocks (instead of 64 Max), and to force high resolution screen allocation to fall on 512K RAM boundaries (a screen can’t split between 512k RAM chunks). Other than that, all programs ran without modification, and it was great running a large enough RAM drive to use as a 720K disk (and backup a full 3.5” 720K disk in one pass).

But Bruce is absolutely right on that they are rare. And they were not easy to install - you had the RAM boards themselves (like the standard 512K ones), but also a DAT daughterboard that had to be soldered to the CPU. The regular 512k boards just required unplugging the 4 old 128K chips, moving some jumpers, and snipping a capacitor or two.


L. Curtis Boyle
curtisboyle at sasktel.net

TRS-80 Color Computer Games website
http://www.lcurtisboyle.com/nitros9/coco_game_list.html



> On Apr 11, 2017, at 2:06 PM, Salvador Garcia via Coco <coco at maltedmedia.com> wrote:
> 
> Thanks Bruce. Much appreciated.
> As far as 512K expansions, I believe that Kip also had one available. Hopefully he'll chime to clarify.
> Regards, Salvador
> 
>      From: Bruce W. Calkins <brucewcalkins at charter.net>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
> Sent: Tuesday, April 11, 2017 2:41 PM
> Subject: Re: [Coco] RAM expansion options for the CoCo 3
> 
> DECB supports 32k of RAM with little ability to effectively use the 
> extra 128 or 512k.  OS-9  Level 2 shines with more RAM. Currently no one 
> is supporting greater than 512k upgrades.  To the best of my knowledge 
> Cloud-9 is the only source of new 512k upgrades.  (Unless you are 
> willing to piggy-back 256k by 4 chips yourself.)  Disto/CRC 1 & 2 Meg 
> upgrades existed, but the hardware was somewhat kludgey needing 
> modifications to some DECB programs and tweaking of OS-9 to work as well 
> as unsoldering the CPU.  NitrOS9 does support 1& 2 Meg units, but 
> Disto/CRC folded up shop decades ago.  What few 1 & 2 Meg upgrade units 
> that exist are seldom parted with and carry quite a premium on eBay.
> 
> Bruce W.
> 
> 
> 
> On 04/11/2017 12:40 PM, Salvador Garcia via Coco wrote:
>> Hi all,
>> What RAM expansion options are there for the CoCo 3 and why would I pick one over the other?
>> I know that Cloud-0 is distributing the Triad, a 512K RAM expansion. Is this capacity the better choice for DECB? For NitrOS9?
>> I have heard of the 2MB RAM expansion, but I don't have any information about it to consider it.
>> 
>> I favor the Triad, but want to make sure that I get the best option for what I need (DECB and NitrOS9).
>> Thanks! Salvador
>> 
> 
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