A500 Agnus Upgrade
4 messages in this thread
I've just upgraded my A500 (it's about 2.5 years old) with the new 1 meg
Agnus chip. I'm now getting 1 meg chip RAM but I'm having some problems.
I installed the chip by doing the cutting and soldering at JP2 and I bent
pin 32 of the Gary chip out of the socket to disconnect the EXRAM line.
I'm now getting 1 meg of chip ram but I have two problems. First, I can't
warm boot the computer. It just sits there flashing the power LED. It
looks like the start of a GURU but never gets there. If I remove the Supra
512K expansion clock-memory card warm booting works again. I tried a CBM
memory card – same thing. Is it possible that those cards won't work with
the new Fatter Agnus? If so, which one will work?
The other problem is PAL mode. I can use a PAL switching program and the
computer seems to go into PAL mode (I get the extra lines) but I can't
resize the Workbench window to fill the screen. It's like the system still
thinks it's in NTSC mode. PAL software won't work either. The screen is
centered correctly but the missing lines are just blank instead of being
off the screen. Is it the PAL programs fault? Which is the best switching
program to use for an A500?
I'd really appreciate any help I could get on this problem!
Bruce,
I'd strongly suspect one of two things:
1. You broke the Agnus socket (or the new chip isn't fully seated)
2. You pulled the wrong line from GARY.
Don
Don,
I double checked the Gary chip. That's ok and the socket looks good. I'm
quite used to pulling chips from that type of socket. I'll try reseating
the chip again. Thanks for the help.
Bruce
:cough: :cough:
Bending pin 32, wasn't the best thing to do. A better solution was to cut
the trace from pin 32 of the 56 pin connector. It connects to pin 32 of
the GARY providing the EXRAM signal.
Since you bent the pin, what you need is to connect +5 volts to the GARY
pin. Check around the GARY for three small pads, I believe you can solder a
wire between the GARY pin and the pads to feed the GARY the +5 volts it
wants to see on pin 32.
I'm not sure about the location of those pads, or if they're on all A500's,
but if you find them — CHECK them first with a meter.
The GARY can be purchased for about $15.00, if you decided to bend the pin
back into the socket (and cut the EXRAM trace), and break the pin.
Ron.