[Coco] Today, I have seen the CoCo 4...

[Frank Swygert]

I was wondering what the SRAM was used for! Other than power and retaining memory powered down, is there any real reason to use SRAM instead of standard DRAM SIMMs on a specially designed board? The CoCo will support at least 2MB, but isn't there a simple hack to allow a max of 4MB (adding an address line or two, IIRC)? Incorporating that in a new design would be ideal, then use a readily available SIMM. Two memory slots should be sufficient if the slots can be made to support from 256K-2MB SIMMs. That would at least make initial cost a bit lower, though memory isn't really so pricey that a board with 4MB would be all that much higher than one with 512K. Not when the overall price of the board is considered. But someone just wanting to run DECB wouldn't really need more than 512K, OS-9 on the other hand benefits from maxing out. If there has to be a choice the board should be optimized for OS-9 (Nitros-9), as the majority of users will probably be running that. As far as I know there is nothing that OS-9/Nitros-9 does that would hamper DECB operation.

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Date: Thu, 27 May 2010 09:49:51 -0400
From:jdaggett at gate.net

On 27 May 2010 at 8:24, Jim Hathaway wrote:


> >  James,
> >  
> >  Does that mean then that you can have a 512k coco3 with a DE-1 and a 1MB
> >  coco3 with the Spartan board?
> >  
> >  Jim
> >  
>    
Essentially yes.
All this talk has rekindled work on a board design that will have 2MB of SRAM. I was planning on using a Spartan 3E in a 208pin QFP. BGA packages are out of the question because the layout would require geater than four layers and a dramatic increase cost. Trying to keep the board below 21 sq inches.


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Frank Swygert
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