src@cs.odu.edu (Scott R. Chilcote) (09/27/89)
I don't know how much use to the Mega 2 owning public this will be, but it was
simply miraculous for me. Apparently, a certain number of Mega 2 STs exist
that have ALL 32 1 Meg DRAMs installed. I KID YOU NOT! I have, put simply,
upgraded my Mega 2 ST to Four MegaBytes of RAM...
SIMPLY BY SOLDERING ONE PIN OF AN IC TO THE MOTHERBOARD.
I don't think _most_ Mega 2 STs have the extra RAM chips, since I have looked
inside a couple of Mega 2s and seen the blank spaces for the RAM chips on the
motherboard. This was what I thought I would find under the hood of my own,
until I opened it to install TOS 1.4. I was shocked, to put it figuratively!
My Mega 2 is slightly unusual. It was sent to the retailer in a Mega 2 box,
with a Mega 2 sticker on the bottom. It had two megs of addressable RAM... but
a Mega ST4 label on the front of the computer. I thought this was strange, but
didn't argue about it since I intended to expand it, eventually, in any case.
But as I said, when I opened it and started counting RAM chips, I found all
four banks of eight chips installed, with no room left over!
How, then, did Atari get it to act like a Mega 2? All of my RAM measuring
utilities had agreed that this was a two meg machine! I began intensively
searching for the reason. It wasn't _too_ hard to find, either!
The Mega 4 uses an IC, labeled U59, to process the MMU signals for the upper
two banks of RAM (U60 through U75). Pin eleven (11) on this IC is RAS2*, the
Row Address Strobe line coming from the MMU. This pin, of all those on the
entire Mega motherboard, was unsoldered! Without this signal the upper two
banks of RAM are invisible to the MMU. I soldered this pin to the motherboard,
and WHAM! Instant upgrade to Four MegaBytes!!
I Have Seen Santa Claus, And His Name Is Tramiel!
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THANKS!!!
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