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

[Aaron Wolfe]

On Thu, May 27, 2010 at 2:11 PM, Frank Swygert <farna at att.net> wrote:
> 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 kn
> ow there is nothing that OS-9/Nitros-9 does that would hamper DECB
> operation.


Since the GIME and even the address lines are essentially software
defined in FPGA, I'd guess you can support almost any amount of RAM if
you wanted to.  However, the only effective use of more than 512k in a
CoCo that I've ever seen is as a RAM drive.  Given the speed of these
boards and the storage options, I don't think a RAM drive is going to
be very important.

Maybe new applications would be created that need more RAM, but with
existing software I find that running out of room in the system page
is more likely than running out of RAM.  Doing a lot of work just for
a huge RAM drive seems wasteful when disks are able to go incredibly
fast to start with.

>
> ----------
> 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.
>
>
> --
> Frank Swygert
> Publisher, "American Motors Cars"
> Magazine (AMC)
> For all AMC enthusiasts
> http://www.amc-mag.com
> (free download available!)
>
>
>
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