Oh - BTW
I just tried full-screen mode on my windows 8.1 box (I have given up on that mode since it scrambles the palette, the driver dont like it ).
In full-screen mode,
scrolling slows to a crawl and stutters.
But if I switch to Windowed mode, scrolling is back to rocket speed, despite now working in full 32-bit colour mode. Plus, I can now see my taskbar and the clock, email notifications etc.
Its faster to convert 256 colour pixels on the fly to 32,000 colour or whatever it is at high-res than try to run in just 256. It used to be t'other way round, back in 2000
!
So if scrolling has become slow - switch to windowed mode at desktop resolution.
Andy