Removed

i.LINK port (SCPH-390xx and earlier)

i.LINK port (based on FireWire 400/IEEE1394 interface) was removed in SCPH-500xx and later.

i.LINK port was mostly used for creating multiplayer network involving multiple PS2 units.

Expansion Bay (SCPH-3000x to SCPH-5500x)

Expansion Bay was last time available in SCPH-5500x, so in last "FAT" model.

Removing the Expansion Bay disallowed games like Final Fantasy XI (11), or Linux to run on slim units.

ATA port (SCPH-700xx and earlier)

ATA port was in theory removed with removing Expansion Bay.

But in SCPH-700xx (first slim model) Sony leaved hardware, and ATA pins required to connect HDD on motherboard.

So ATA port was really removed in SCPH-750xx and later.

IOP (aka MIPS R3000A/PS1 CPU) (SCPH-700xx and earlier)

Used by PS2 as the IOP or as the CPU used to run PS1 games (is the same CPU that PS1 had).

Since SCPH-750xx units, IOP was replaced by PowerPC CPU that emulates IOP.

This resulted in some minor, or major compatibility issues for PS1/PS2 game titles.

System update ability (SCPH-900xx with BIOS v2.20 and earlier)

In BIOS v2.30 and v2.50 Sony removed support for system update software via memory card to block FMCB exploit.

The system update exploit used this ability to inject own code into console RAM, and allow to run custom code that way.

BIOS v2.30 can be found in majority of SCPH-900xx units,

while BIOS v2.50 can only found in Europe-only KDL-22PX300 Bravia units.

SPC970-based MechaCon (SCPH-390xx and earlier)

It was replaced with Dragon MechaCon found in SCPH-500xx and later.

Component/RGB video output (SCPH-900xx with BIOS v2.30 and earlier)

This feature was removed in BIOS v2.50 found in Europe-only KDL-22PX300 Bravia units.

ProtoKernel BIOS (SCPH-10000/15000)

This feature was scrapped with the welcome screen (OOBE) found in SCPH-18000 and later.

Static RSOD until pressing RESET button or insert disc (SCPH-18000 and earlier)

Press RESET button or insert disc to get rid of the RSOD, this odd behavior was scrapped in SCPH-3000x and later.

PCMCIA port (SCPH-18000 and earlier)

This feature was removed in SCPH-3000x and later.

Buggy DVD Player v1.00J (SCPH-10000 with BIOS v1.00)

This feature was removed in SCPH-10000/15000 with BIOS v1.01 and later.