I have a theoretical question for you: Do you think the MB would
work if the on board RAM were disabled and additional RAM were installed
into the RAM slot? Most MB's adjust the RAM when polled upon start up.
Supposed (and most people would never attempt to do this) the on board
RAM were disabled by opening the CAS and RAS lead or even the power lead
for the IC? Would the first RAM seen then be that installed in the
slot? Just curious.
That is a good question. Based on the way regular motherboards,
chipsets, and BIOS work, I would say there is no special dependence
on soldered down memory. The situation could be quite different
for some older equipment. But modern stuff doesn't really
care which slots are populated.
As far as I know, you don't need RAM to start the boot process.
And the Northbridge is likely disabled, as far as memory operation
goes, and is turned on by some of the BIOS code. That is why
there should be more flexibility about what bank(s) have to be
working.
You'd have to be careful, with respect to what you cut. If you
have a "private" signal on the memory bank you can play with,
that might be OK. But snipping any controlled impedance, bussed
signals would be a more dangerous proposition.
Still, I like your idea. If you could figure it out, then chances
are you could try exactly what you suggest.
One thing I can't tell you, is whether a modern BIOS is dependent
on having a working SPD chip or not, for each slot. The BIOS
actually has two ways to config/test memory. It can use the SPD EEPROM
and the declared config information, to understand what size memory
is installed. But the BIOS can also do probes on the memory, to
verify the size (that is how the BIOS can properly configure
a computer, even when the contents of the SPD are wrong). What
I can't tell you, is whether the hooks are still in
the BIOS, to do Plug and Play based purely on probing. If it
had the capability to probe, then disabling the SPD chip would
not be enough to prevent the memory from being detected.
And then you'd have to go after something like a CS#.
The soldered down memory might have an SPD chip, which is what
I'd attack first. Followed by looking for something like CS#.
Since I don't know what hides under that "gold colored material"
in the pictures, I don't know how difficult it would be to
disable the memory on the OPs board. We'd really need to see
a closeup photograph of what is underneath. If it was just a
regular SODIMM, the removal/disabling might be rather easy.
I don't really see much advantage to the manufacturer soldering
memory chips right to the motherboard, because of the danger
the memory might not pass on a factory memory test. It would
be more of an advantage for the memory to be modular and
removable.
Paul
