[NTLK] eMate memory upgrade (was: High resolution images of eMate mainboard)

[Frank Gruendel]

>> I've added images of an eMate mainboard that might come in handy for 
>> all who like to tinker with or repair eMates.

> Nice. There are two unpopulated RAM chips. Do you have an organ donor
> that you could use to add DRAM and NVRAM to a working board and see what
happen?

If you haven't a clue what I'm talking about, this image might help...

	<http://preview.tinyurl.com/3vsm6kd>

Also, you might want to have a look at the Apple eMate memory upgrade
discussion: 

	<http://support.apple.com/kb/TA38458?viewlocale=en_US>

Actually, there's but one unpopulated installation space. RC1 looks like
one, but isn't.

The unpopulated installation space is most likely not for DRAM. The DRAM is
in U14 and U15.

I assume that when the eMate was developed, the developers weren't sure what
size of Flash RAM chips would be available at a reasonable price when the
eMate would be ready to be shipped. This happens quite often, and normally
you'd layout your board in a way that will allow for different chips to be
installed.

So they layouted the board in a way that at least three different sizes
could be installed: U16 (smallest), U17 (medium) and either U19 or U9
(largest). As we can see, they settled for a LH28F016 Flash RAM chip in U19,
which provides the 2MB x 8 that the eMate comes with by default.

If the Apple developers DID have a Flash RAM extension in mind, it can be
safely assumed that they would have chosen two identical chips. So an
additional chip would have to be installed in U9, since U9 is the only
unused installation space that has 56 pins like the LH28F016 in U19. But
maybe they simply put U9 there for a chip with yet another pinout.

This being so, and yours truly being a cautious person, I recently asked
David aka PCBMan for an opinion on the chances of success in this kind of
surgery. He told me that U9 is not for an additional chip, but for a
DIFFERENT one. Since he's usually well informed, I refrained from simply
soldering a donor chip there. Instead, I checked if this installation space
could be for a LH28F016 at all. This would require at least that the supply
voltage and ground pins are the same. Alas, even that isn't the case. So,
unfortunately, David is right, and such an attempt would fail miserably.

However, if you look at one of the eMate upgrade boards, for example the
MicroTech one,

	<http://preview.tinyurl.com/3moejva>

you'll see that a Flash RAM upgrade with just one additional LH28F016 Flash
RAM chip is definitely possible. But I do not intend to design a new eMate
memory upgrade board.

But maybe there would be another way...

The LH28F016 has three unused pins. So it would be possible to put up to
eight times (2 x 2 x 2) the Flash RAM into such a case without the need of
additional pins.

Given the fact that the original chip's name is LH28F016, chances are good
that chip manufacturers would have named these chips LH28F032, LH28F064 and
LH28F128. Believe it or not, but there's a LH28F032 out there that has the
same pinout as the LH28F016 except for pin 3. In the LH28F016 this pin is
not connected, in the LH28F032 it selects between the lower and the upper
half of the memory.

Just to prove how helpful it is to have an unpopulated board, I had a look
at pin 3 of U19. If Apple had never wanted a larger memory chip, this pin
wouldn't be connected to anything. But it is. It is connected through a via
to U18 on the opposite side. U18 is a five pin IhaveNoIdeaWhat, and it is
(not surprisingly) not installed.

Depending on the foresight of the Apple developers, it might have been
within the realms of possibility that 64MB and 128MB chips would work, too.
Unfortunately, though, the other two unconnected pins of the LH28F016 aren't
connected to anything on the board, so this isn't possible. Apart from that,
there doesn't seem to be a LH28F064, and the only LH28F128 I've found
doesn't come in the required package.

The next task would be to find out what U18 would have been, had it been
installed. Once we know this, it shouldn't be much of a problem to figure
out what other components might need to be added around U18 to make the
larger size chip work. Replacing the Flash RAM chip wouldn't be easy, but it
can be done. Given the fact that the board was designed for a larger chip, I
have no doubt that the eMate's OS would support it. Especially since in the
2x00 it'll work quite happily with twice the amount of Flash RAM that the
eMate comes with.

Frank

-- Newton software and hardware at http://www.pda-soft.de