Sony’s magic grey box

Console BIOS

The BIOS design differed depending on the region and the model number of your console.

CD Player: A basic CD player that plays Redbook CD audio and is controlled by the PlayStation controller, additional functions are supported.

  • Shuffle function: Order of tracks is randomly decided and plays tracks in a different order each time
  • Program function: You can decide the order in which tracks are played
  • Repeat: Same track can be played repeatedly
  • Soundscope: Only in the SCPH7000 models and later, audio visualizer
  • Sound effects: different sound effects that can be applied

Memory Manager: Items on both memory cards can be deleted and copied to another memory card for backup purposes.

Memory Cards

The console supports the use of two memory cards simultaneously. However most games will only use Memory card slot 1, with slot 2 being rarely used outside of a handful of titles, for this reason it was relegated to being used for backup purposes which could be done using the memory card manger in the BIOS.

The storage capacity is fixed at 128k and is divided upto 16 units called blocks, and upto 15 blocks can be stored per memory card with one being hidden. This hidden block is used to save the game title text and icon for each save. Some games may use two or even three blocks. Higher capacity memory cards were made available, but because the console was designed to see 15 blocks per memory card, they had to circumvent this by offering different banks of 15 blocks which can be switched by pressing a button on the memory card to cycle between them. Some memory cards could be switched by pressing a combination on the controller upto boot up, since the controllers and memory cards shared the same bus. In practice this became tedious since you often had to press the button repeatedly to find the bank that the game data was saved on unless you manually made a note on which bank stored which game save.

I guess they never though people would play more then 15 games, then again a few games didn’t support the memory card at all, with games like Doom using passwords instead.


The console featured two controller ports that connected a multitude of peripherals to the system. The type of controller supported was dependant on the controller itself, with some being able to fall back to emulating a digital controller should the software not support that controller

Digital Controller: The standard issue controller that was the default from 1994 to 1997, features a directional pad, four face buttons and four shoulder buttons (R1,R2,L1,L2) and Select/Start buttons.

Analogue Controller: Adds two analogue sticks to allows for flexible directional control instead of using the d-pad, the Japanese version features vibration. This controller can replicate the Flight stick

DualShock: Adds vibration function with a motor with different strengths is built into the left and right grips, for all regions Also comes with dual analogue sticks that the analogue controller introduced

NeGcon: Early form of analogue controller released by Namco for use with Ridge Racer games, and supported by a few third party driving/racing titles also. You twist the controller to simulate steering.

Jogcon: Developed by Namco for Ridge Racer Type four, digital controller with a circular wheel in the middle that was supposed to give a more accurate feel of steering and force feedback.

Flight Stick: Two large joysticks with analogue sticks for flight shooters

There was also an official mouse and various third party accessories like a dance mat and a light gun.

Misc Accessories

Multitap: allows up to 4 controllers to be connected through a single port, can only be used with a supported game. Two multitaps can be connected to allow for 8 players on one screen. Heck with a serial cable you could have up to 16 in plone game, don’t think any games supported that.

Serial cable:  Used for the serial link to connect two consoles together

Rear I/O

AV Multi Out: Supports a multitude of video output options, RF out way typically bundled with the console, with composite, S-Video and RGB also being supported with the correct cable.

Serial: Used to connect with another console for multiplayer, supported in a limited amount of titles and requires 2 copies of each game. On the Net Yaroze this was used to connect the console to a PC using its RS232 port.

Parallel IO: never officially used by Sony, was used to expands the capacities for the console but was actually used for the Gameshark/Action Replay devices to enabled cheats. More recently used for the PSIO optical drive replacement.


The main CPU features a MIPS R3000A based core clocked at 33.8Hz, along with a GTE (Geometry Transformation Engine) and the Data Decompression engine on the same die. The CPU is built and designed by LSI as part of their CoreWare range, where an OEM can specify and build their own integrated/embedded CPU. These were popular in various consumer electronics such as satellite receivers where they integrated the CPU, MPEG2 decoder and the DVB demodulator onto one package, cutting down on the cost to the end user and simplifying the board layout.

GTE (Geometry Transfer Engine)

This processor is responsible for generating the 3D graphics the console rellies upon and is on the same die as the CPU and is addressed by the R3000A as COP2. By running geometry operations, this relives the CPU of this task, in comparison many PC 3D accelerators relied on the CPU to generate the polygons for them, which could become a bottleneck if the game engine itself is CPU dependant. This game the PSone impressive 3D performance compared to PC at the time of release, for a fraction of the cost.

Unlike most common 3D accelerators, the GTE lacks supports for floating point arithmetic due to how demanding it is, instead the GTE was integer based in order to produce a high speed rendering system. This gives off inaccuracies with the 3D graphics as ‘seams’ can sometimes form between polygons, which is visible on certain games. There is little to none perspective correction which can cause textures to be distorted at certain angles, since the console cant map them accurately to the players view point. Lastly, a lack of a hardware Z-buffer can cause issues with polygons overlapping, unless one is implemented in software.

A later revision of the GTE seems to exist called the GTE-2, however not music is known regarding the differences between the two, its possible that GTE2 is a die shrink version which is common for console 3-4 years into their lifespan.

CXD8654: CPU on the Namco System 12

CXD8530AQ: CPU on the Namco System 11, could also be used on the home consoles

CXD8530BQ: CPU on the Capcom ZN1, also on SCPH-1000

CXD8561Q: SCPH1002 CPU

CXD8606Q: CPU on the SCPH5000-9000

CXD8606BQ: Later revision CPU on the SCPH9000

Graphics Processing Unit

Very different from a modern PC GPU, this is responsible for rasterising the 3D graphics that have been generated by the GTE and applying the texture mapping effects. There are two revisions of the GPU

The first revision uses VRAM based memory for its framebuffer, which is dual ported RAM, of which is also connected to the video encoder. This allows for the video encoder to grab the frame data straight from the VRAM and convert/display to a PAL or NTSC display. This revision was used from the original 1994 to late 1996.

The second major revision uses the cheaper SDRAM which is only single port. This means the GPU needs additional data lines to export the rendered image to a video encoder. This was fairly common for console released in late 1996 onwards, and is considered to be the standard GPU of the system. The reason for the change was because SGRAM was a lot cheaper than VRAM based memory, however there were differenced in how the consoled performed with the memory change, and as such developed had to test their systems against both configurations. This is why the debug units have two colours, as the blue contains the old VRAM GPU.

To the end user there is very little difference between the GPU, depending on the game and the video standard/cable being used. The VRAM model ha increased banding due to only 5bits being used when modulating the texture colour, the SGRAM GPU uses 8 bits. Both GPUs have the same clock speed – 26.84MHz

CXD8514Q: Old GPU with VRAM

CXD8538Q: Namco System 11 GPU


CXD8561Q: Revised GPU with SGRAM

CXD8561BQ:Revised GPU with SGRAM – SCPH5000

CXD8561CQ: Minor revision, 1999

CXD8661R: Namco System 12 GPU

CXD9500Q: Later revision GPU for the PSone model which has onboard SGRAM



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