PlayStation

Sony’s PlayStation emerged from a failed Nintendo partnership and transformed the industry. CD-ROM capacity enabled cinematic experiences; developer-friendly architecture attracted third parties; marketing positioned gaming for adults. The PlayStation won its generation decisively, establishing Sony as a gaming giant and proving that console gaming was mainstream entertainment, not just toys.

Fast facts

Manufacturer: Sony Computer Entertainment.
CPU: a customised R3000A, 32-bit RISC, at 33.8688 MHz, little-endian.
Caches: 4 KB instruction — and a data cache that is not a cache.
Coprocessor: GTE, the geometry transform engine, working in fixed point.
GPU: draws triangles and rectangles; Gouraud shading; 2 KB texture cache.
Colour: 15-bit direct (32,768) or 24-bit direct.
RAM: 2 MB main, 1 MB video, plus 512 KB of sound buffer the CPU cannot address.
Sound: SPU, 24 ADPCM voices at 44.1 kHz.
Media: CD-ROM.

Designed by subtraction

Sony’s hardware manual is most revealing in what it says is missing.

There is no memory management unit. The R3000A normally has a TLB; Sony’s does not:

a TLB, which is the virtual memory management device for the R3000 CPU, is not mounted. Therefore, the relationship between the physical address and the logic address of the memory space is always fixed.

There is no floating-point unit. The GTE does the geometry, and it does it in “fixed-point format matrix and vector operations”. Every transform and lighting calculation on the machine is integer arithmetic with an implied binary point.

The data cache is not a cache. This is the detail with the longest consequences:

The D cache of the PlayStation is called a Scratch Pad.

One kilobyte of memory at a fixed address, as fast as cache, but the programmer decides what is in it. A cache guesses; a scratch pad is told. On a machine with no virtual memory and no floating point, that kilobyte is where the working set of a transform loop lives, and using it well is most of the difference between a PlayStation game that holds its frame rate and one that does not.

Set against the PC Engine, the comparison is almost comic. Hudson gave an 8-bit processor eight mapping registers and a two-megabyte address space. Sony took the memory manager out of a 32-bit RISC chip. Both were right: the PC Engine needed to reach past 64 KB, and the PlayStation needed every cycle to be predictable.

Triangles and rectangles

One line in the GPU section explains a great deal about how PlayStation games look:

The polygons handled by GPU are triangular and rectangular.

The hardware draws quadrilaterals directly rather than splitting everything into triangles — a choice most later hardware did not repeat. Combined with the fixed-point pipeline above, it is a plausible mechanism for the vertex instability PlayStation games are remembered for: coordinates reach the GPU already rounded, and a four-sided panel carries that rounding further than a triangle would. That connection is this Vault’s inference, not Sony’s — the manual documents the fixed-point GTE and the rectangular polygons separately and draws no line between them.

Textures come from “texture pages” of 256 × 256 pixels in the frame buffer’s non-display area, fed through a T-cache the manual sizes at 2K bytes — a small window onto the texture data, which is why texture layout and drawing order mattered so much on this hardware.

The sound system, and where CD audio goes

Sony’s Table 4-1 is three lines: ADPCM, twenty-four simultaneous voices, 44.1 kHz. The SPU is not just a sample player, though — its voices carry “automatic modification of operating parameters which take pitch transformation and time as coefficients”, so pitch and envelope move under hardware control rather than per-frame CPU writes.

Its waveform memory is a wholly separate 512 KB:

This is a 512KB local memory which supplies waveform data to the sound source. It is not mapped in the CPU address space.

Not addressable by the CPU, and not only for samples — the same buffer doubles as “a reverb work area which functions as an effector”, and as a staging area when moving sound back to main memory.

CD audio does not bypass the SPU. This is the detail worth correcting, and it explains why PlayStation soundtracks sit in the same acoustic space as the effects over them:

The audio output of the decoder temporarily enters the SPU, is mixed with the SPU output, and then becomes the final audio output via a reverb unit.

Everything leaves through the reverb unit — streamed CD tracks included.

Why it won

PlayStation’s advantages:

CD-ROM: massive capacity, cheap manufacturing.
Developer support: reasonable licensing, good tools.
Third parties: Sony courted developers Nintendo alienated.
Adult marketing: positioned for older audiences.
Game library: Final Fantasy VII, Metal Gear Solid, hundreds more.

Industry impact

What PlayStation changed:

Media format: CD became console standard.
Demographic: gaming aged up.
Competition: Sega effectively defeated.
Franchises: enabled new blockbuster series.

The disc revolution