Is there any real difference between PC3-8500s and PC3-8500f?
It's Laptop memory, DDR3. Would a laptop which can take one also be able to use the other?
PC3-xxxx is a module designation for DDR3 RAM.
There are several variations that are indicated by the trailing letter (the s or f on PC3-8500s and PC3-8500f). The Wikipedia link doesn't mention s, but here are the variants it does list:
Fully buffered DIMMs are notched differently than standard RAM packages, so they physically will not fit in a slot meant for other types of memory.
The s may refer to SO-DIMM, which refers to the physical RAM package (the circuit board and connectors); if so, it indicates that this RAM is for laptops. Regular desktop memory is simply called DIMM.
You'll need to check your laptop specs to be sure which RAM it takes. Make sure you get RAM with the right package (SO-DIMM vs DIMM) and module (PC3-8500 vs PC3-8500f vs PC3-6400r vs et cetera ad nauseum...).
Not sure what the above guy is talking about. I came up across this page also while wondering what laptop PC3-8500F was.
However, it's definitely not FB-DIMM. FB-DIMMs were only made for DDR2 on Intel dual 771 chipsets (5000, 5100, 5400). Once you've see how hot those things run (hot enough to fry bacon on), you'd know they'd never be in a laptop.