Wait, how is the system going to know and why would it care what rpm the HDD is?
“Wait, how is the system going to know and why would it care what rpm the HDD is?”
That’s actually 2 questions, general & specific.
The user installing the correct RPM HD is important so that files are read correctly. Street signs meant for reading at 35 mph are much harder or impossible to read at 95 mph, LOL.
The Bios has to have the device specs in order operate the device correctly and to pass info to the OS, so those specs are either auto detected on boot (from info passed by the device) or the specs are manually entered (old style, lol) into the bios by the user when a new device is installed. The Bios needs # of sectors and cylinders of the HD in order to determine its size. It may or may not get RPM speed, but the MB can’t manage the HD correctly if the HD spins too fast for the chipset &/or bus to handle.
If the HD RPM is too fast, then the bios can not auto-detect correctly and no user entered specs would be correct.
This problem occurred on older MBs having ATA/IDE buses for drives instead of SATA. SATA has ability to run either 5400 or 7200 RPM drives. The difference is the bus change from parallel to serial and vast improvement in data transfer speed.