getting rid of the jailbar pattern — #3

Post #3 by sbreit

Source Forum	68kMLA
Category	Troubleshooting
Post Date	Fri, 13 Apr 2012 - 11:39
Original URL	https://68kmla.org/bb/threads/getting-rid-of-the-jailbar-pattern.25160/

Post

Hi zuiko21 and thanks for your reply!

The VRAM contents could be copied from DRAM sometimes, but also from ROM, from other sections of the VRAM itself, or even directly computed.

That's interesting... thanks for the info!

·To be precise about sync signals: [...]

You're absolutely right, thanks for the clarification. I've put it very simple, that's why I said "oversimplified"

·The SE/30 has 64 K of VRAM, over twice the required amount for the screen (about 22 K). This is in order to implement double buffering so the screen updates cause no flickering [...] But I think there are two VRAM chips for bandwidth reasons

Okay, now I consider the mystery of the 2 VRAM chips solved

I've puzzled over this with a friend of mine... we couldn't quite figure it out.

Thus, the culprit is likely to be the UE8 shift register -- OR the lines connecting its inputs to the VRAM output lines.

This also is what said frend and I came up with... Should be the most likely source of error in the overall picture - at least so far.

Hope this helps,

Sure will! Thanks!

Regards

Steffen