@mrbombermillzy, here is a test picture that explains what happens, namely, when displaying the picture, the bit manipulation of the data bus is activated for the second shifter.
On a STe, the picture looks like this :
- testpix2-on-ste.png (19.94 KiB) Viewed 2107 times
You can see a dark stripe under the light grey pixel, and nothing under the blueish pixels. On the twin shifter, the dark stripe will also appear under the blueish pixel (if I counted the pixels correctly), following the mapping here (e.g. bit 14 of the databus is fed to bit 14 AND bit 9 on the data input of the Shifter) :
- fantom-pixel-source.png (35.96 KiB) Viewed 2107 times