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Fix for STE's with damaged blitter chip by santosp (Read 394 times)
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Fix for STE's with damaged blitter chip by santosp
03.02.09 at 17:59:43
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This is the english translation of the fix presented by santosp for STE's with damaged blitter chip. As we all know blitter chips are the easiest to break on an STE right with the mmu.

The symptoms that revealed that something was wrong with the blitter chip were a system hang on TOS 1.62 when one moved the mouse pointer to the top bar and a general malfunction on TOS 2.06, such as inability to boot without a disk in the floppy drive while the system would hang on any attempt to activate the blitter. Also a delay or a system hang would appear on any attempt to switch resolution. Of course those may not be common problems or can be a result of other h/w failures.

The solution to this problem isn't quite as simple as removing the chip using a plcc extractor since that would not eliminate the problems. The solution lies to the fact that to the Atari, the blitter is an external coprocessor and not embedded to the system operation. In that respect santosp discovered a footnote in the atari schematics pertaining to the STE that said what needed to be done incase the STE was sold without the blitter.

The solution to this case is to remove the chip using a PLCC extractor and bridge or add two 0 Ohm resistors in the R111 and R112 positions on the motherboard as shown in the following pictures.

After that and if the Blitter is the only problematic chip in the STE the machine should work without problems with the blitter indication in TOS 2.06 becoming unselectable.

ATTENTION: After the mod is done, the blitter chip must in no way be put back in the motherboard unless the bridges or the resistors are removed first.

Hopefully this was helpful. Many thanks to santosp for this usefull mod.

« Last Edit: 03.02.09 at 18:00:42 by Christos »  

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