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U202/203: Chips That Overheat
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Many A3000 owners complain of strange graphics and disk errors,
like windows and gadgets being trashed. Sometimes dots and horizontal
lines will appear. This is likely due to the U202 and U203 components,
a pair of Programmable Array Logic chips (format: 16L8-10) which tend to
overheat. This is likely because they are in a part of the
case where circulation is nearly nonexistent, especially when you have lots
of hot disks and cards. These chips control various CHIP RAM DMA access
issues.
The Commodore part references are 390526-02, 390527-02.
Notes from Anthony Hoffman:
All of the A3000 original PAL devices (U202, U203, U701, U714) can be replaced with modern GAL devices which have
better performance and lower operating temperatures than the original PAL logic.
Using the CUPL sources files provided by Dave Haynie, I have compiled JEDEC
files for programing GAL16V8 devices using CUPLPLD 4.2a.
Thanks to Tobias Seiler for the original conversions and information.
Click here to download U202, U203, U701, U714 JEDEC files. Note that you'll
need a suitable GAL programmer.
These have been tested in the A3000 using Lattice GAL16V8D-15QPN (Farnell part number 969-9678) but should work for
Atmel and other 16V8 PLDs.
The original Amiga PALs are 25ns, which happens to be equivalent to the slowest available 16V8 devices. Therefore any
device whose part number matches 16V8*-**QP* (* = any character) should in theory work. The 20-pin
DIP/DIL package is required.
You can view the Lattice 16V8 datasheet for more information.
I can also program and supply these parts as required. Email me for more information and pricing.