3 ms·

One of the reasons why you could switch modes mid-frame is because the concept of a "video mode" is fundamentally different on a PC than on an Atari or Amiga. O

One of the reasons why you could switch modes mid-frame is because the concept of a "video mode" is fundamentally different on a PC than on an Atari or Amiga. On a PC, ever since the EGA, the adapter can output at different horizontal and vertical scan rates and the monitor can adapt to the requested mode from the video card. That's why switching video modes takes a couple seconds and may involve a "click" or two. Upon mode switch, the monitor must resync to the new signal. On the Atari and Amiga, the horizontal/vertical scan rates are constant; the only thing that changes is how scanout turns pixels in video memory into signals for the CRT.

M95D 4y ago
No. I have a Sony G520 CRT monitor with a hardware switch. When I flip the switch, the other image appears in less than a second. In the past I had a Samsung (I don't remember the model) that made the switch without even interrupting the electron beam, in mid-frame. First 2 frames were garbage, until it sync'd to the new signal, but it only took a blink of an eye to switch (at 85 Hz). It was also very quick to sync after a mode change. I could see BIOS screens that modern flat displays are to slow to display before they dissapear.
- aceazzameen 4y ago
  Oh man, I miss my Sony G520. It's still the best monitor I owned. I haven't had a monitor that nice since I gave it away a decade ago. It was still in great condition at the time too.
reaperducer 4y ago
On the Atari and Amiga, the horizontal/vertical scan rates are constant I can't speak to the Atari, but my memory is that this is not true of the Amiga. The Amiga could do this amazing thing where it would display multiple resolutions on a monitor at the same time, divided horizontally. Analog was flexible that way. An Amiga could even display two different resolutions from two different sources on the same monitor at the same time. This was part of my workflow when I used an Amiga to do live TV news graphics around 1990.
- bitwize 4y ago
  Yes, because the scan frequency didn't change -- that's what I'm trying to say (my terminology may have been a bit off). The timings of the horizontal and vertical sweep of the beam were constant; upon mode change the CRTC changed how scanout occurred, doubling the width or height of pixels in lower resolution mode but it didn't change the scan frequency, allowing the mode change to occur while the beam kept moving along. PC monitors were analog too, but with PC monitors from EGA onwards, changing modes meant potentially changing scan frequency, which required the monitor to sync with the signal at the new frequency. Apparently a high-quality Sony monitor could do this instantly but many of us were slumming it with monitors that took a while to sync.
  - Moru 4y ago
    The Amiga could do a lot more than the Atari with the gfx chip. The Atari had three modes, 320x200, 640x200 and 640x400 so two horizontal and two vertical resolutions. It also can change frequency between 50 and 60 Hz but that wasn't instant, it took a couple of frames to stabilize. This I think you could use to get borderless screens with even higher resolution but I've forgotten exactly how it worked. For the highest resolution you needed a better monitor though so I didn't have much experience with that one. The Atari Falcon also had more resolutions with instant switch but my memory is getting quite fuzzy there :-)

M95D 4y ago

No. I have a Sony G520 CRT monitor with a hardware switch. When I flip the switch, the other image appears in less than a second. In the past I had a Samsung (I don't remember the model) that made the switch without even interrupting the electron beam, in mid-frame. First 2 frames were garbage, until it sync'd to the new signal, but it only took a blink of an eye to switch (at 85 Hz). It was also very quick to sync after a mode change. I could see BIOS screens that modern flat displays are to slow to display before they dissapear.

aceazzameen 4y ago
Oh man, I miss my Sony G520. It's still the best monitor I owned. I haven't had a monitor that nice since I gave it away a decade ago. It was still in great condition at the time too.

reaperducer 4y ago

On the Atari and Amiga, the horizontal/vertical scan rates are constant I can't speak to the Atari, but my memory is that this is not true of the Amiga. The Amiga could do this amazing thing where it would display multiple resolutions on a monitor at the same time, divided horizontally. Analog was flexible that way. An Amiga could even display two different resolutions from two different sources on the same monitor at the same time. This was part of my workflow when I used an Amiga to do live TV news graphics around 1990.

bitwize 4y ago
Yes, because the scan frequency didn't change -- that's what I'm trying to say (my terminology may have been a bit off). The timings of the horizontal and vertical sweep of the beam were constant; upon mode change the CRTC changed how scanout occurred, doubling the width or height of pixels in lower resolution mode but it didn't change the scan frequency, allowing the mode change to occur while the beam kept moving along. PC monitors were analog too, but with PC monitors from EGA onwards, changing modes meant potentially changing scan frequency, which required the monitor to sync with the signal at the new frequency. Apparently a high-quality Sony monitor could do this instantly but many of us were slumming it with monitors that took a while to sync.
- Moru 4y ago
  The Amiga could do a lot more than the Atari with the gfx chip. The Atari had three modes, 320x200, 640x200 and 640x400 so two horizontal and two vertical resolutions. It also can change frequency between 50 and 60 Hz but that wasn't instant, it took a couple of frames to stabilize. This I think you could use to get borderless screens with even higher resolution but I've forgotten exactly how it worked. For the highest resolution you needed a better monitor though so I didn't have much experience with that one. The Atari Falcon also had more resolutions with instant switch but my memory is getting quite fuzzy there :-)