[Coco] [Color Computer] updated wikipedia article

[jdaggett at gate.net]

Art 

To me it appears to point someone unknowing of the Coco Internals 
as thinking the two are near identical. At least that is my perception. 
Then I maybe out of bounds from the rest of the group.

james

On 17 Nov 2005 at 15:07, Arthur Flexser wrote:

Date sent:      	Thu, 17 Nov 2005 15:07:37 -0500 (EST)
From:           	Arthur Flexser <flexser at fiu.edu>
To:             	CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject:        	Re: [Coco] [Color Computer] updated wikipedia article
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> I'm not really seeing the "glaring" error.  To say that the SAM

> contains a duplicate of the VDG's 12 bit address counter does not deny

> that the SAM might have more address bits available as well, just that

> 12 of its bits would normally duplicate the VDG's 12 bits.

> 

> Art

> 

> On Thu, 17 Nov 2005 jdaggett at gate.net wrote:

> 

> > Mike 

> > 

> > One glaring error that I see is in the following paragraph:

> > 

> > Due to limitations in 40 pin packaging, the SAM contains a duplicate

> > of the VDG's internal 12 bit address counter. Normally this

> > counter's settings are set to duplicate the VDG's display mode.

> > However this is not required and results in the creation of some new

> > display modes not possible when the VDG is used in a system alone.

> > 

> > The linear address counter for video memory in the SAM chip is a 16

> > bit counter and not a 12 bit counter. Setting the F0-F6 flip flops

> > allows the video ram to be set on any 512 byte boundary within the

> > 64K memory map. This difers from the MC6847. The VDG supplies the

> > lower 12 bits of address and has to rely on external address decode

> > logic to be able to map where video ram was located in 8K

> > boundaries. Due to the increase capabilites of the SAM chip's linear

> > address generator for video memory, the SAM chip inconjucntion with

> > the VDG allowed increase of three semi graphics video modes.  

> > 

> > Also someone unfamiliar with the Coco line would think that the

> > MC6883/74LS783 and the MC6847 were developed exclusively for the

> > Coco. This inference would not be true. Each chip can operate with

> > any 8 bit computer on its own and not with exclusively with the

> > MC6809/MC6809E.  Furthermore the MC6883 and the 74LS783 are the same

> > chip. The SAM chip is LSTTL logic and was done on a bipolar line as

> > opposed to the VDG chip which is High Density NMOS and done on a MOS

> > line. I am not sure that this is the "gospel" as to how it got two

> > part numbers but one possibility is related to which camp the part

> > went to. If sold under the LSTTL catalog it would have the 74LS783.

> > Conversely if sold under the Motorola Computer Products it had the

> > MC6883 label. I vaguely remember around the 1980 time frame that

> > there was a growing number of parts that carried dual numbers and 

> > there was a cleanup or consoldation of internal/external

> > documentation. 

> > 

> > Finally the ACVC or GIME is woefully breif if one is trying to give

> > a technical description of the hardware. The GIME chip is not 100%

> > backwards compatible. It is not just an integration of the MC6883

> > and the MC6847. It is by far a more complex IC than the previous

> > pair and a design of its own from the ground up.  

> > 

> > james

> > 

> > On 16 Nov 2005 at 19:52, Mike Pepe wrote:

> > 

> > To:             	ColorComputer at yahoogroups.com

> > From:           	Mike Pepe <lamune at doki-doki.net>

> > Date sent:      	Wed, 16 Nov 2005 19:52:32 -0500

> > Copies to:      	Subject:        	[Coco] [Color Computer] updated

> > wikipedia article Send reply to:  	CoCoList for Color Computer

> > Enthusiasts <coco at maltedmedia.com>

> > 	<mailto:coco-request at maltedmedia.com?subject=unsubscribe>

> > 	<mailto:coco-request at maltedmedia.com?subject=subscribe>

> > 

> > > Hi listers,

> > > 

> > > I was working on a "CoCo Tech" web page, but when I saw the entry

> > > for the Atari 8 bit machines on wikipedia I decided to integrate

> > > my work there instead.

> > > 

> > > http://en.wikipedia.org/wiki/TRS-80_Color_Computer

> > > 

> > > now includes a lot of hardware information, though I'm not sure if

> > > that would really be of interest to most people.

> > > 

> > > Comments are welcome.

> > > 

> > > -Mike

> > > 

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