CD drive

Overview

Supports speeds of 1x and 2x and can switch between them.

Electronics

The CD subsystem of a first generation PU-7-based PlayStation consists of the following hardware components:

• Sub-CPU/Mecha-Con
• CXD1199BQ: CD controller (with 32 KB of external RAM)
• CXD2516Q: CD DSP
• CXA1782BR: Servo controller + RF-amp
• BA6398FP: CD Driver

Over the years, these components have been consolidated into fewer, more complex ICs.

Models (mechanism)

• KSM-440AAM
  • Compatible with PU-7, PU-8 and PU-16 boards
  • Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
• KSM-440ABM
  • Compatible with PU-7, PU-8 and PU-16 boards
  • Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
• KSM-440ACM
  • Compatible with PU-7, PU-8 and PU-16 boards
  • Can in theory be mounted on PM-41 boards after replacing the top plastic shield, but the cable doesn't have the reinforcement/pull-tab for the non-ZIF connector of PM-41
• KSM-440ADM
  • Compatible with PU-18 and PU-20 boards
  • Has a plastic shield at the bottom to prevent the long cable running under the mechanism from getting jammed in it
• KSM-440AEM
  • Compatible with PU-22 and PU-23 boards
• KSM-440BAM
  • Compatible with PM-41 boards (PlayStation One)
  • Can be mounted on PU-7/PU-8/PU-16 boards after replacing the top plastic shield (these boards have a ZIF-connector, but installation works fine nonetheless)

Copy protection + Region locking

On optical drives (CD, DVD, BluRay etc) the laser automatically follows the groove by moving the lens sideways. This is necessary, since tracks on optical discs are neither perfectly centered nor perfectly circular. The PlayStation exploits this inherent feature of the CD format by having a specially crafted wobbly groove at the beginning of each original disc. The console now monitors the tracking movements the laser has to do to follow this groove and extracts a signal out of this. After this, a string can be extracted from that signal. This string is either SCEI (for Japan and Asia discs), SCEA (for North America discs) or SCEE (for all PAL region discs). The console then compares this to a string it expects, which differes depending on the region of the console. Hence, this method combines both, copy protection and region locking.

The exact way this signal is being extracted by the drive electronics and how it's compared differs between motherboard revisions. E.g. PU-7, PU-8 and PU-16 have the circuit built from discrete op-amps and passive components; PU-18 and PU-20 use a custom analog IC, and PU-22 and all later boards do all of this inside the DSP/CD-ROM controller/SPU combo IC.

The extraction circuit requires adjustment on PU-8, PU-16, PU-18 and PU-20. The potentiometer setting is called "Push-Pull" in official documentation and - on some board revisions - also labeled as such on the board. On PU-8 and PU-16, the potentiometer is RV702. On PU-18 and PU-20, it's RV703 (and also the only potentiometer on these boards).

Additionally, some PlayStation BIOS (depending on both, the region and the revision) also implement some further checks, which unlike the wobble signal check are not done by the drive hardware but completely in software. These checks involve checking the content on the PlayStation logo screen, which is actually loaded from disc and not part of the BIOS. Either the logo, the licensing text, or both are checked.

Lastly, some games implement their own copy protection measurements, e.g. LibCrypt. As additional protection, some games check for the presence of a modchip and won't work properly if they detect one, no matter if the game disc is original or not.

Issues

Mechanical

• KSM-440AAM, KSM-440ABM and early KSM-440ACM have their optical pickup blocks in a plastic case rather than the cast metal found in all later units. This causes the arms that slide on the drive block's chassis to wear down pretty quickly by friction, thus skewing the laser out of adjustment. This is an infamous issue on early PS1 consoles. It is not caused by heat; instead it is just premature mechanical wear. Placing the console on it's side as has been famously done by many owners of early PS1 consoles back in the day only causes the laser to not slide on that rail at all, as it will mostly "hang freely" in the air around that rail.
  • Fix: Replacing either the whole drive unit with a late KSM-440ACM or even a KSM-440BAM (from a PS One, see notes above in the models section) or just the optical pickup with one of the aforementioned drive unit models.
• Dust covering the top of the lens
  • Fix: Dust on the external lens surface can easily be cleaned off using just a cotton swab, optionally with some CD/DVD lens cleaning fluid (as can often be found as part of DVD drive cleaning sets)
    • Hint: Don't use isopropyl alcohol, as it will dissolve and smear around even the smallest amounts of fats and oils that landed on there with the dust, leaving them as smeary residue on the lens. If you used isopropyl alcohol, you need to additionally wipe the lens a bit with a dry cotton swab or - even better - proper lens cleaning fluid.
• Dust getting inside the optical pickup
  • Fix: to do