Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.programming > #6685

Re: Mystified by an Atari 2600 demo.

Show all headers | View raw

On 6/11/16 9:00 PM, J. Clarke wrote:
> In article <njhpte$3hn$2@dont-email.me>, usenet@coloraura.com says...
>>
>> On 6/10/16 5:41 PM, J. Clarke wrote:
>>> In article <23c1e131-543c-4654-85b0-f3876f484635@googlegroups.com>,
>>> cdalten@gmail.com says...
>>>>
>>>> In the demo, the guy enters the coordinates(?) to a sprite. Right after that, this sprite then gets displayed on a screen. Right after that, he is able to do things like type text and clear the screen. This is done without impacting the sprite.
>>>>
>>>> The question is how can such a primitive system display two things independently of each other? To the best of my knowledge, the system didn't have threads nor multiple processors. The only clue I got was the guy said that hardware based sprite generators were something the engineers came up.
>>>
>>> You don't need threads or multiple processors, just an interrupt
>>> controller.
>>
>> Which isn't actually how this works at all.
>>
>> As others have pointed out, it was specialized hardware which controlled
>> the video output.  So you had basically two parallel processes going on,
>> one on the CPU, and another on the TIA [1]
>>
>>
>> [1]: https://en.wikipedia.org/wiki/Television_Interface_Adaptor
>
> If you're using memory mapped video there is necessarily some device
> transforming the memory map into a video signal.  If you think that the
> 1.19 MHz CPU is somehow taking bits from the memory map and generating a
> 6 MHz NTSC video signal from them you need to learn a bit about signa
> processing.  The video controller at the time was a fairly dumb piece of
> equipment that nobody considered to be a "processor".  It wasn't like
> modern GPUs that are by '70s standards supercomputers in their own
> right.
>
> See if you can find a Heathkit microprocessor trainer on ebay with the
> manuals, and do the exercises in them.  When you're done with that
> you'll have a _much_ better idea of how things really worked in that
> era.
Did you read about the TIA?  It was also interesting to read about the 
ANTIC, which was even more powerful.

In both cases, the display isn't merely "memory mapped", there is other 
processes going on in the video chips.  I'm not talking about GPU 
processing.

Back to comp.programming | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Mystified by an Atari 2600 demo. Chad <cdalten@gmail.com> - 2016-06-08 16:05 -0700
  Re: Mystified by an Atari 2600 demo. Kaz Kylheku <545-066-4921@kylheku.com> - 2016-06-08 23:51 +0000
    Re: Mystified by an Atari 2600 demo. Chad <cdalten@gmail.com> - 2016-06-08 19:10 -0700
      Re: Mystified by an Atari 2600 demo. Kaz Kylheku <545-066-4921@kylheku.com> - 2016-06-09 04:18 +0000
  Re: Mystified by an Atari 2600 demo. Kaz Kylheku <545-066-4921@kylheku.com> - 2016-06-09 00:01 +0000
  Re: Mystified by an Atari 2600 demo. commodorejohn <commodorejohn@gmail.com> - 2016-06-09 09:47 -0700
  Re: Mystified by an Atari 2600 demo. "J. Clarke" <j.clarke.873638@gmail.com> - 2016-06-10 20:41 -0400
    Re: Mystified by an Atari 2600 demo. Daniel Pitts <usenet@coloraura.com> - 2016-06-11 12:47 -0700
      Re: Mystified by an Atari 2600 demo. "J. Clarke" <j.clarke.873638@gmail.com> - 2016-06-12 00:00 -0400
        Re: Mystified by an Atari 2600 demo. Daniel Pitts <usenet@coloraura.com> - 2016-06-12 21:08 -0700
        Re: Mystified by an Atari 2600 demo. Randy Howard <rhoward.mx@EverybodyUsesIt.com> - 2016-06-13 04:12 -0500

csiph-web