old 4200
new dv6-1352dx
old 4200 - not listed on Curcial; but maybe DDR2 PC2-5300
new dv6-1352dx - Package: 200-pin SODIMM; DDR2 PC2-6400
If PC2-5300 used together with PC2-6400, all memory will function at slower 5300 speed, 166MHz clock instead of 200MHz clock. You might notice it and you might not, depending what you use laptop for.