Sinclair ZX80 / ZX81 / Z88 Forums

1024MAK wrote: ↑Tue Oct 30, 2018 9:42 pm To put it another way...

<waits for confirmation that you want me to continue...>

Mark

50hz slow, 60hz even slower.

OK, I did my 50hz/60hz switch mod.

Hard to tell the difference display wise on my monitor. I thought the K looked a bit lower and the screen maybe a bit greyer?? But I couldn't tell.
So to see if my switch was working, I decided to run a speed test.
I found a basic program on this forum talking about 50hz and 60hz Zeddiesto be used for a speed test, so I typed it an and tested.
(Glad I could flip the switch without power cycling and re-typing. It was only like a 6 line program, but still. )

So, results.
With the switch one way, it completed in 19.73 seconds.
(Well, not completed, as I stopped it when I saw the first result number display on the screen, but it still works for the test.)

With the switch the other way, it completed in 30.06 seconds. (Well, again I stopped it when the first result showed up.)

So, I am guessing the first switch direction is 50hz and it is about (at least for that test) a third faster than the 60hz test.
Wow. That is significant!
(Which makes me wonder if I will ever use it in 60hz mode. Perhaps there is a game that I need to slow down a bit? )

And it looks like my switch worked! Yay!

The switch will only affect software that reads it's position.

Sinclair's BASIC ROM reads the 50/60 position, to create the right picture.

But some software made in machine language might not read the position and hardcode/assume 50 or 60.

desiv wrote: ↑Wed Nov 14, 2018 4:07 am (Glad I could flip the switch without power cycling and re-typing. It was only like a 6 line program, but still. )

desiv wrote: ↑Wed Nov 14, 2018 4:07 am And it looks like my switch worked! Yay!

Yes, the Sinclair ROM code reads the 50/60Hz pin every time it generates a TV line. So if a switch is connected to this pin, you can switch between 50Hz and 60Hz on the fly when using BASIC.

Mark

mrtinb wrote: ↑Wed Nov 14, 2018 9:57 am The switch will only affect software that reads it's position.

Sinclair's BASIC ROM reads the 50/60 position, to create the right picture.

But some software made in machine language might not read the position and hardcode/assume 50 or 60.

Thinking this might be the case for me with swaotch basic hi-res graphics demos... not sure.