Actually a very good guess! I had the same problem with Starblaze on a few screens so decided to investigate the annoying behavior after finding this thread. Looking at the code that writes to the screen it is really badly implemented. When updating the screen it sends an LCD command to set the position on the screen then an immediate LCD data write followed by a loop of 50 LCD data writes with a delay between each of the writes. So if the screen is fast then it will get 51 data writes looping around on the 51st causing the screen to jitter. If the screen is slow then it works without a problem, missing the 1st data write. Bottomline the screens are fine and show variable performance, as might be expected. I did not check to see if it had anything to do with the LCD voltages but the screens are fine the app is poorly implemented.
Leaving a confirming response in case anyone else gets frustrated trying to check jittering screens with Starblaze. From: M100 <[email protected]> on behalf of Kenneth Pettit <[email protected]> Reply-To: <[email protected]> Date: Tuesday, July 16, 2019 at 2:42 AM To: <[email protected]> Cc: <[email protected]> Subject: Re: [M100] Starblaze 100 strange behavior on select LCDs > The controllers on the LCD module are actually quite slow. The main ROM polls > the controller¹s ³busy² register after each write. > > My guess is that to achieve maximum speed, Starblaze isn¹t doing this poll and > instead pushing the controller a bit faster than it was designed for. I > haven¹t ever disassembled the Starblaze code, but I would bet it just uses a > CPU loop to delay a bit between LCD writes. What is likely happening is that > some controller chips are ok with this and others are not. > > Of course this is just a guess. > > Ken > > Sent from my iPhone > > On Jul 15, 2019, at 1:24 PM, Serhiy Sosonniy <[email protected]> wrote: > >> I recently bought this nice game on cassette and tried on some of my M100, >> and immediately noticed strange artifacts on some units, text would shift, >> lines or dots would appear. It seems artifacts appear on some LCDs and do not >> on others. I tried swapping LCDs and problem follows the LCD, "good" LCD >> works fine with any motherboard and "bad" always has artifacts. No artifacts >> in M100 menu or standard programms. So what can it be? >> >> https://youtu.be/MCzEvpL9LFI >> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2 >> FMCzEvpL9LFI&data=02%7C01%7C%7C6a45381e9eb74c459f1308d709975174%7C84df9e7fe9f >> 640afb435aaaaaaaaaaaa%7C1%7C0%7C636988417816322905&sdata=5LPyMm1J3SfcoC8ViIY2 >> CHv%2BJy%2FQ9JOGn5iKnWKvkHo%3D&reserved=0> >>
