ijor

I just received the very first, preliminary, die shots for CTIA after decapsulation. Please note that we are still very far from reverse engineered schematics. Just a few comments for the holidays Thanks to the "donors", Bob and Bryan.

In the first place, CTIA and GTIA share an almost identical die layout. GTIA is a CTIA layout, patched and slightly modified. The patch looks so clean that, conceivable, the CTIA layout was done considering already a possible patch path to GTIA.

For a moment, I considered that perhaps it might be the other way around. That CTIA is a patched GTIA (with the extra circuit removed). But at the very least, the L0 routing is obviously a late patch on the GTIA die.

It doesn't seem to be any "GTIA logic" in the CTIA circuit. In other words, CTIA doesn't seem to have any GTIA functionality whatsoever (not even disabled). So the theory that CTIA could be a non working (correctly) GTIA, with GTIA capability perhaps internally disabled, seems wrong.

The L0 pin is connected to the die, but configured as an input. It is never driven.

The George Mc Leod name was signed on the CTIA layout. But for some reason, it was removed from the GTIA layout.

GTIA chip decap (NTSC version)

Once again, thanks to Greg James and the people at Visual 6502 for the physical decap, die shooting and image stitching. Thanks to Bryan for donating the chip. Reverse engineered schematics coming soon.


Rough floorplan:

 GtiaFloor.jpg   1.7MB   164 downloads

We are seeking a CTIA chip for decapsulation and reverse engineering.

Bryan donated one some time ago (together with a few other Atari chips). Unfortunately, it got damated during decapsulation. It sometimes happens

If anybody has a CTIA chip that is willing to donate for this purpose, please let me know. You will be mentioned as a contributor (as long as you don't want to remain anonymous). Again, we are seeking a CTIA (the rare older one), not a GTIA chip. We are already working on GTIA, and expect to provide results shortly.

Pokey reconstructed schematics in searchable PDF format:

 PokeyReSchem.pdf   290.75K   302 downloads

Thanks to the Greg James ( from Visual 6502) for decap and taking the die shoots, and to Ivo for donating the chip. See the first page for notes and comments.

I'd recommend using this together with the (unreadable) original schematics, and the excellent work by Perry and Piotr done at Pokeydocs (should be somewhere here in this forum, just note one wrong cell on each channel counter).