Reply 20 of 21, by Thermalwrong
xnplater wrote on 2025-09-07, 19:55:According to the CT65548 manual, this may not be possible. […]
MAZter wrote on 2025-09-06, 23:39:Additionally I tested utility with Sager Model 86 (800x600, Chips&Tech 65548) and it does not change anything (VEXP tool not working with this model too). It's probably use complete different registers.
And this resolution really bothers me, but I think it's a feature of the laptop model. I will be glad if you expand compatibility with Chips&Tech 65548.
According to the CT65548 manual, this may not be possible.
While vertical compensation uses the same repeat every N-th line algorithm that can be tuned by changing N, the horizontal compensation only mentions doubling for graphics modes. For text modes it does mention expanding 8 pixels to 9 or 10, but it is not stated if this applies to graphics modes as well.
We could definitely give it a try, but I suspect that both horizontal and vertical compensation are already being used here to maximum effect. What can be done is to reduce the vertical stretching to keep the 4:3 aspect ratio, but that would also make a blank border on top and bottom, basically a 640x400 picture centered within 800x600 😒
That matches what I've found, even C&T's own tools can't do horizontal stretch of 320*200 with 800*600 panels beyond doubling to 640 pixels wide: Re: The quest for the perfect retro laptop: a saga
I spent a while poking around registers with a more basic utility but couldn't get it to do anything other than double with the 65548 chipset. Shame too, quite a few of my laptops have that chip.
I'll have to give your tool a go with my Compaq Armada 1598DT, which has a C&T 68554 graphics chip and a 1024*768 LCD panel. Scaling is already implemented pretty well on it though so it might not make much difference. Is the 68554 register compable with the 6555x chips?