This is the place to discuss our glorious C64/128 machines and their very active scenes. Other C= 8-bits welcome, too!
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intric8
Seattle, WA, USA

by intric8 posted Wed Nov 28, 2018 9:02 am

Folks, some pretty major C128 news dropped last night.

Tim Harris of The Shareware Plus Commodore 64 & 128 Blog:
I am pleased to confirm the new LumaFix 128 developed by e5frog has now finished testing and has now entered production and will be available during December.


A little unpacking of that sentence above is needed:
"e5frog" is the moniker for a man from Sweden well-known in the C64 scene. He and several others (chrisyboy, Pyrofer, others?) worked together to try and find a comparable solution for the C128 as the LumaFix 64 Mod. On some C64s, the VIC-II video chip can produce what are known as "jail bars" or other patterns of interference.
LumaFix64_out-of-the-box-600x450.jpg
Photo credit: Breadbox.com


MtnBuffalo via Breadbox.com:
The cause of the vertical lines artifact is basically unwanted interference generated from clock signals stemming from the VIC-II graphics chip. The noise-introducing-signals include the AEC line (related to bus access), CAS and RAS signals (related to memory access), BA signal (bus availability) and PHI0 (clock related). Practical tests have shown that the primary sources of the interference is intimately connected to the AEC and PHI0 lines and the PHI0 affects the borders more than the AEC does.

The checkerboard pattern artifact (or thin green and red colored lines) is mostly related to the Chroma signal of the S-video output. The problem is most visible when using the Commodore 64 with a modern TV. It can be reduced by adjusting the voltage level of the Chroma signal.

Reducing the vertical lines problem can be done by inverting the sources of the artifacts (the interfering signals) and blend them back into the picture by an adjustable amount. On a practical level, a device called LumaFix64 was created based on the combined forces of the C64 community and made available by different producers online either as a kit or as an assembled ready-to-use product. The version reviewed here was designed by e5frog and manufactured by Tim Harris of Shareware Plus. It is basically a little printed circuit board that is placed between the VIC-II graphics chip and the motherboard of the Commodore 64. It has a standard 40 pin female IC socket on top for placing the VIC-II chip in and a 40 pin male header pins on the bottom for fitting the device into the socket on the motherboard. It has small potentiometers for adjusting the AEC and PHI0 signal (vertical lines) and the Chroma signal (checkered pattern).


And the C128 has always had this issue as well, if not worse. Even on CRTs, the jailbars can be very pronounced.

The LumaFix 128 could be a fantastic solution for this 30 year-old issue. No word yet on where they will be sold (perhaps Tim Harris will sell them?) and for how much. The LumaFix 64 goes for $30 these days and is a simple drop-in mod.
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robdaemon

by robdaemon posted Wed Nov 28, 2018 4:16 pm

Oh, this is great. My 128DCR exhibits this on the Commodore monitor I use. It'll be nice to clean up that output.
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joethezombie

by joethezombie posted Sun Jan 20, 2019 10:07 am

Heads up fellow Amiga <3 s, C128 division-- these are now available!
Check it out
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intric8
Seattle, WA, USA

by intric8 posted Sun Jan 20, 2019 10:31 am

Thanks for the heads up, Joe!

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