The mask definitely sets a limit alhough it isn't as hard as a LCD etc. with acutal fixed pixels, because a dot in the triad can show info from more than one logical pixel in the incoming video signal. Beam from one line can partially light up a physical phosphor dot and the next line can light up that same one and you get to see info that would otherwise have gotten fully lost instead of partially. In a sense it gives a level of subpixel rendering for "free", it is one of the reasons why going past mask limits still gives something that isn't completely ass to look at, at least when the limits are not gone past by a huge amount 🤣. Horizontally though, things happening between the triads, for one color, is lost but you get info from a different pixel on a different color between, so there's another temporal layer on the mix which helps to enhance legibility by a slight amount. The same way can be used on LCDs etc. also if one really wanted to.

A CRT always has infinite “monochromatic “ resolution, just means rainbow colored striped text if your resolution exceeds the isotope pitch.

If the dot size is too big or blurred the edges of too small of details overlap or blurr together

I wondered why the 400 line had 70Hz instead of 60Hz for the video cards? Suppose, one redesigned the VGA chip to do this 60Hz instead of trying to find monitors that works with 70Hz even many times results in frame skip ?

Cheers,

Both have the same line frequency and this is the key thing. It requires no modification to line deflection section and any connected HV sections. Multisync monitors are much more complicated in line deflection + HV side by comparison and original VGA monitor is not multisync at all.

pentiumspeed wrote on 2025-08-16, 15:43:

I wondered why the 400 line had 70Hz instead of 60Hz for the video cards?

Because the short persistence phosphor used in VGA monitors (which avoids any kind of motion blur) causes noticeable flicker at 60Hz, which annoys a lot of viewers. 70Hz is more ergonomic than 60Hz on CRTs.

pentiumspeed wrote on 2025-08-16, 15:43:

Suppose, one redesigned the VGA chip to do this 60Hz instead of trying to find monitors that works with 70Hz even many times results in frame skip ?

You don't need to redesign the VGA chip, you just need to make changes to the way the chip is programmed. The BIOS sets up the mode as 70Hz mode. The VGA BIOS has an standard option to load custom parameter tables, and you can install a patched table that has some or all modes adjusted to the vertical total amount of the 480 line mode, which will drop the frequency from 70 Hz to 60 Hz.