Hello, I wanted to check with folks whether my efforts to identify the
memory capacity of a SIMM, based on the chip part numbers. If my
calculations are correct, you'll see that it leads to another question.
The SIMMs were sold to me as 32MB EDO modules. Each module has 8 chips (4
on each side) and the chips are Micron chips marked MT4LC16M4G3 DJ.
Breaking down this part number and decoding it, I get MT=Micron Technology,
4=SDRAM, LC=3.3v, 16M=16megabit depth, 4=4bits wide,G3=8K refresh
addressing, and DJ=SOJ package.
The main thing I'm interested in is using the 16 megabit x 4 bit capacity of
the chips to figure the capacity of the total module. My understanding is
that I calculate the capacity of the chips by multiplying depth x width,
which in this case equals 64 megabits (16megabits x 4bits). Since there are
8 chips, the total capacity of the the module is 8 x 64 = 512 megabits.
Divide this by 8 to change from megabits to megabytes and you get 64 MB
capacity for the module.
Assuming the above is correct, why is this module being sold as a 32MB
module?
I ended up trying to figure out the capacity of these modules, because the
first system I tried them in only detected the pair as a total of 32MB (16MB
each). This may be a limitation of the motherboard I was using, a P100
sytem with a FX chipset (no documentation available). I tried them in a
somewhat newer motherboard with a TX chipset, and they were detected as a
total of 64MB in this system (32MB each), which is what they were advertised
as.
My hunch is that these modules are 64MB modules that failed to operate
properly at full capacity, but rather than discard them, they were labeled
32MB and offered for sale. Does this sound reasonable? Anyone else run
into something like this? Any reactions to this? For some reason I feel a
bit duped. (Of course if my number crunching assumptions are wrong, I'll
just feel chagrined.)
TIA,
John
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