[Coco] 1 or 2 meg upgrade

[Mark Marlette]

As Bill and Gene have explained.
AKA: MMU
2bits = x4 * 512K
More bits = Paul Barton's design.

The DAT board was the 2 bit extension of the MMU from Tony D.

Mark Marlette
http://www.cloud9tech.com
mark at cloud9tech.com

      From: Bill Pierce via Coco <coco at maltedmedia.com>
 To: coco at maltedmedia.com 
 Sent: Saturday, November 22, 2014 6:53 AM
 Subject: Re: [Coco] 1 or 2 meg upgrade
   

Nick, that's exactly what the "dat" board does, "switches" the extra bits needed to get more memory.
So you got an extra bit.... who's gonna switch it? what's it gonna switch?
It all has to be electronically tied to something, and in this case, the 6809, since it's what's gonna access the memory.
My only regrets with the system I have, is that they didn't put a 6309 in when they put the 1-meg in, but I don't think the 6309 was known about at the time or that would've been done too.
The "dat" board hovers above my 6809 with ALL lines tied to all pins of the CPU. A 2nd 512k board sits directly above the 1st with circutry to tie the 2 together. The 2-meg board is a little different, but not much.
I can revert to 512k at any time just buy pulling the power line to the dat board (with power off of course).


Food for thought... how many more graphics pages and sprites for extra game levels and rooms could you store in another 512k-1.5meg?
 

Bill Pierce
"Today is a good day... I woke up" - Ritchie Havens
 

My Music from the Tandy/Radio Shack Color Computer 2 & 3
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-----Original Message-----
From: Nick Marentes <nickma2 at optusnet.com.au>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Sat, Nov 22, 2014 2:56 am
Subject: Re: [Coco] 1 or 2 meg upgrade


I'm must say that I'm in agreement with Aaron... "512K should be enough 
for anyone!".  :)

But I do understand that OS-9, being a "real OS", can work better with more.

Having said that, I don't necessarily think that is a good thing. We all 
use to complain how Windows was a memory hog and nothing but "bloatware" 
but here with OS-9, we turn our heads and say that it's good.

I'm interested efficiency and that is an area I have high praise for so 
when I hear that 1Mb is great having more video display space or that 
one can run more text editors and load more drivers, my mind starts to 
spin and I start asking why? Is OS-9 that inefficient?

I personally don't feel one needs more than 512K on a CoCo but I do 
understand that OS-9 could use it. Then again, I don't see OS-9 as being 
a part of the CoCo (my opinion). The CoCo is just another 6809 based 
platform for running this OS.

It was designed for engineers and embedded applications. But as a 
mainstream level OS running multiple general user applications,  it 
really seems to me like a multitasking version of CP/M with the DOS 
level complexity of old Unix.

Not a bad thing if you're into that (and I suspect many on this list 
are) but for an application developer developing commercial grade 
applications (me), it doesn't spur my creative interest.

Having said all this, even though I said I can't really see a use for 
more than 512K on the CoCo, if 1/2Mb could be done easily, it would be a 
nice novelty for CoCo users and certainly great for the dedicated OS-9 
users.

Just a technical sidenote (will someone yank this guy off the air!), 
couldn't 1Mb be used as 2 x 512K memory banks and using a spare bit 
somewhere to switch between the two? What about the unused bit on the 
RGB port?

Nick

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