WAV files of the same song ripped on 3 different CD readers are not the same

I’m new to this stuff, so please, forgive me if I’m asking a stupid question.

I have a brand new audio CD, EAC in “accurate” mode and 3 readers:
Plextor PX-708A (Firewire)
Yamaha CRW-F1E (Firewire)
HL-DT-ST DVD-ROM GDR8081N (DVD drive in my IBM laptop)

Here are the results of my rip & compare tests:

  1. All WAV files have EXACTLY the same lengths.
  2. All WAV files from the SAME drive are EXACTLY (bit by bit) the same. (I did about 10 rip/compare cycles).
  3. Files from different drives are ALWAYS SIGNIFICANTLY different when compared (bit by bit).
  4. When compared (files from different drives) by EAC Compare Tool, I’m getting the following: “Error type - nnn missing samples/ Position - 0:0:0:0”. It’s always Position 0:0:0:0 but different numbers: 520, 750 etc.

What am I missing?
Thanks for the advice.

My guess is this is caused by Sub-channel/Main-channel skew. Each drive will have a slightly different skew, so when starting to read at the beginning of the disc, there may be a few bytes difference in the exact starting location between the drives. The TOC tells the software exactly how long the tracks are so the file size should always be the same no matter what.

If you open 2 of the images with a hex editor and find the first non-zero byte, you will probably see that they are at different offsets in each image. If you start comparing from that point on, they will probably match until the very end where the length is different.

Someone else may have other ideas.