IPS Screen Mods and 59.7Hz

[Auyx]

Hi Everyone,

The original GBA, GBC and GB had 59.7 Hz screens.

I know there are now a number of new drop in screen replacements for the GBA from third party's.

My question is how do these screens designed to run at 60Hz handle this? Do they run with dropped frames, stutter or input lag or do they run the GBA too fast like a lot of emulators do?

How does the Analogue Pocket handle this discrepancy?

 

[FAST6191]

I have never seen anybody ponder this and don't think I have ever seen in discussed in homebrew (vblank timings being all the rage/basic intro to graphics systems http://coranac.com/tonc/text/video.htm , https://problemkaputt.de/gbatek.htm#lcddimensionsandtimings mentioning it only in passing and all too keen to talk about oddities and failures in other aspects, latency discussions being had for the gb player in stuff like https://www.retrorgb.com/gameboyinterface.html but possibly a different discussion) or emulator dev circles (including the otherwise massively anal about timings audio hacking aspects). I have seen people measure the different clock speeds between hardware revisions but screen wise... a few might measure frame rates in the games themselves but eh.

In general video the drop of frame rate from the line frequency was usually a thing done to allow colour on CRT screens to work better and kind of irrelevant even for the LCDs of the GBA era. Not to mention most screens don't have an internal clock (certainly not one the system itself cares about) and will instead take a clock pulse/sync pulse from the device itself.

Similarly on "too fast" are you really able to detect 0.3Hz?

With the previous I am obviously unable to comment on the realities other than to say I played several tight timings based games as part of my analogue pocket review, having played said same on stock hardware (give or take flash cart*) GBAs predominantly for many years. Would have picked up something if it was a thing.

*what, if anything, changes here I can speculate a bit on. Some complained about Mother 3 timings in some things but I have never found anything drilling into that and whether it is the game, the translation, the flash cart or something else that is getting in the way.

 

[Auyx]

Well the reason I was thinking about it was I was jumping between my real GBA playing Mario Kart Super Circuit with an AGS-101 screen and my RG35xx running the mGBA retroarch core and noticed that the game felt a little more skittish on my RG35xx. So I started both games on the same course at the same time and watched the clock. The clock on the emulated console ran over 2 seconds faster over the course of the 10 mins the timer will run.

It got me thinking though if the modded screens are just dropping frames then they should still run at OG speeds but with added stutter.

 

[Latiodile]

wouldn't the screen be configured to run at 59.7hz then?

also emulators could run faster because of emulator inaccuracies alone, since the gba is the real hardware it'd probably push the frames it intends to push and the IPS mods are probably configured to only run at the required refresh rates


i don't have an ips modded gba, just an ags 101 modded one, so i'm talking out of my ass and only saying this based on what i know of how hardware works

 

[Fishaman P]

Though it's theoretically possible for a screen to have an internal framebuffer and its own internal vsync, it's _far_ more likely it just scans as the GBA tells it to, i.e. 59.7 Hz.

 

[ciaomao]

Well the reason I was thinking about it was I was jumping between my real GBA playing Mario Kart Super Circuit with an AGS-101 screen and my RG35xx running the mGBA retroarch core and noticed that the game felt a little more skittish on my RG35xx. So I started both games on the same course at the same time and watched the clock. The clock on the emulated console ran over 2 seconds faster over the course of the 10 mins the timer will run.

It got me thinking though if the modded screens are just dropping frames then they should still run at OG speeds but with added stutter.

fps delta =0.5%; fps missed in 10min = 30frames —> 0.5s .
2s time discrepancy is not caused by the lcd timing

 

[ghjfdtg]

These backlit screen mods have solved this for a good while now. They will simply clock the LCD panel at the GBA's native clock rate or a multiple. These LCDs may be designed for 59.9 Hz but that doesn't mean you can't clock them slower. The difference here is negligibly small.

 

[ciaomao]

These backlit screen mods have solved this for a good while now. They will simply clock the LCD panel at the GBA's native clock rate or a multiple. These LCDs may be designed for 59.9 Hz but that doesn't mean you can't clock them slower. The difference here is negligibly small.

true. there is always a min/max clock specified.

 

[Dogson]

Analogue Pocket has a variable refresh display, it will display it properly.

Screen mods for GBA (any of the current kits like Cloud Store Gaming, Funny Playing and Hispeedio kits will update at native refreshrates, it's a solved issue there. (not updating at proper refresh as you said leads annoying to occasional stutters, the further away you are from target refresh, the more stutters)

With your emulation handheld you should set the timing skew allowance to be something high, that way the game will slightly speed up to 60Hz (in this case it's fine to run just slightly faster, it's a sub 1Hz negligible difference) as that will give you buttery smooth motion as 60Hz is matching your FPS exactly. As long as you aren't getting stutters from the emulation device not being powerful enough to play at target framerate (dips).