I'll just answer this old post here:
Can this emulator run games without any scaling/stretching? I've read Atari 2600 games run at 160x192, although the vertical resolution may vary. This means, the horizontal image can be doubled in size to fit the 320 pixels, so the result would be a sharp image, without any hint of scaling.
If you look at a screenshot of Stella there is no blending, just crisp pixels.
The GCW0 version is rendering a 320x240 screen. Stella internally horizontally scales the image from 160 to 320 so it just renders two of the same pixel at a time. There is no vertical scaling. From the optimising perspective, the GCW0 hardware scaler
doesn't scale horizontally (as far as I know) so wouldn't be of much use here yes it probably does if you turn off aspect ratio preservation
. Even if you could use the GCW0 hardware scaler for this task it is unlikely to produce significant speed gains.
However the actual resolution of the Atari is not easily definable due to the way it uses the CPU to render. There is an interesting (5 yr old) discussion on this subject here
Here is an interesting youtube video about Atari 2600 rendering, the Atari 2600 part starts at 3:24.