copy down the numbers on the chip,
go to the chip manufacrturer to check the datasheet or use the number decoder.
you can't tell by the numbers directly unless you've the number decoder in your mind.
define your high density first -
if you mean larger size chip,
if your 128MB is 8 chips on one side only, they're 128Mbit chips, it doesn't work in early stepping bx mb. You can call it high density when comparing to old 64Mbit chip.
if you mean 32x4 type chip,
your 128MB shouldn't be using this type chips, 32x4 chips appear in those cheapy generic 256MB module.
(32x4 is 128Mbit, 16 chips - each side 8 chips, made up a 256MB module. Regular 128Mbit is 16x8, there is also 8x16 type.)
32x4 type chip shouldn't be called high density, the density is same as 16x8 type, just different architecture.
