Re: Installing GS RAM card in slots 1-7

["Charlie" <charlieDOTd@verEYEzon.net>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message 
Fs-dnSEbycNoqWXWnZ2dnUVZ_vGdnZ2d@giganews.com">news:Fs-dnSEbycNoqWXWnZ2dnUVZ_vGdnZ2d@giganews.com...
> rich12345 wrote:
>> On May 22, 12:28 pm, "Charlie" <charlieD...@verEYEzon.net> wrote:
>>> I'm having trouble getting my mind wrapped around this 
>>> statement.
>>> Could you clarify it?  Specifically why is it necessary to 
>>> access
>>> both the AUX memory and main memory in the same cycle?
>>
>> AUX RAM and MAIN RAM need to be accessed in the same cycle
>> for 80 column text and DHGR graphics.
>>
>> 1/2 of the video data is in MAIN, the other 1/2 is in AUX.
>>
>> Same cycle:  It takes 2X the time to display 80 columns compared
>> to 40 columns.  It takes 2X the time to display DHGR compared to
>> HGR....
>
> Actually, it takes 2x the number of *bits*, in exactly the same 
> time
> (1 cycle), so the need to access both main and AUX memory 
> concurrently.
>
> Only one address bus is needed, but two data busses are required.
>> If you access AUX at a later cycle, then you add to the time to
>> update/refresh the video output.
>>
>>
>> (maybe?)
>
> Very close.  ;-)

My reason for asking is that I've been trying (without much success) 
to get DHR working on the Carte Blanche card.  If it is impossible 
I'll feel really good when I achieve it :-)
Anyway, because of my lack of success, I've been trying to learn 
more about how DHR works. That's why I am concerned about your 
statement.  If all the DHR video data doesn't appear on the 
peripheral slot bus I'm in deep trouble.

Not being a hardware guy I figured that if data from the AUX memory 
and main memory were placed on the peripheral bus sequentially but 
interleaved then the it must have been accessed that way (not 
concurrently).
The CB card does *seem* to pick 80 column data off the peripheral 
bus so I figured it could do DHR as well.  Am I wrong?

Charlie