Nintendo 64 technical specifications

The Nintendo 64 technical specifications describe the console's processor, memory, and other components.

Components

See also: Nintendo 64 programming characteristics

• CPU: 64-bit NEC VR4300 (MIPS R4300i) with 24 KB L1 cache, running at 93.75 MHz
  • Performance: 125 MIPS (million instructions per second), 93.75 MFLOPS (million floating-point operations per second).
• GPU: 64-bit Reality Coprocessor, running at 62.5 MHz and over 100 MFLOPS. It is a microcode-reprogrammable T&L GPU, composed of two integrated processors: the Reality Signal Processor (RSP) and the Reality Display Processor (RDP).
  • Video Interface (VI) reads data from the frame buffer using a fixed time interval, and sends it to the DA (digital-to-analog) converter (video DAC) to produce the video output.
  • Audio Interface (AI) reads data from the audio buffer using a fixed time interval, and sends it to the DA (digital-to-analog) converter (audio DAC) to produce the sound output.
  • Peripheral Interface (PI)
  • Serial Interface (SI)
  • Hardware features include detailed texture mapping with perspective correction, anti-aliasing, Z-buffering, trilinear filtering, Gouraud shading, 256 levels of alpha channeling, and level of detail management.
• Audio: 16-bit, stereo, CD quality.
  • Number of ADPCM voices: 16-24 channels with pitch-shifting PCM, up to 100 PCM channels possible.
  • Sampling frequency: 44.1 kHz or 48 kHz, selectable
• 4 MB RDRAM (Rambus DRAM) on a 9-bit 562.5 MB/s bus, upgradable to 8 MB with Expansion Pak
• ROM cartridge (Nintendo 64 Game Pak) bus running at 264 MB/s
• Resolution: 240p (320×240), 288p (384×288), 480i (640×480), 576i (720×576), widescreen via letterboxing and anamorphic compression
• Color palette: 16,777,216 (24-bit color depth), 2,097,152 possible colors (21-bit color) on screen.

The Nintendo 64 motherboard, showing CPU, RCP, and RDRAM

Central processing unit

The Nintendo 64's central processing unit (CPU) is the NEC VR4300, a less expensive derivative of the 64-bit MIPS Technologies R4300i. Built by NEC on a 0.35 µm process, the VR4300 is a RISC 5-stage scalar in-order execution processor, with integrated floating-point unit, internal 24 KB direct-mapped L1 cache (16 KB for instructions, 8 KB for data). The 4.6 million transistor CPU is cooled passively by an aluminum heatspreader that makes contact with a steel heat sink above.

With a clock rate of 93.75 MHz, the N64's VR4300 is said to be the most powerful console CPU of the fifth generation of video game consoles. Except for its narrower 32-bit system bus, the VR4300 retains the computational abilities of the more powerful 64-bit MIPS R4300i, though few titles take advantage of 64-bit data precision operations. N64 game titles generally use faster and more compact 32-bit data-operations, as these are sufficient to generate 3D scene data for the console's RSP (Reality Signal Processor) unit. In addition, 32-bit code executes faster and requires less storage space, which is at a premium on the N64's vintage cartridges. The CPU is challenged by a 250 MB/s bus to the system RAM, and in order to access the RAM, the CPU must go through the Reality Coprocessor (RCP), and can not use DMA to do so as the RCP can. This challenge is further compounded by the RDRAM's high access latency.

Tools that emulate the Nintendo 64 benefit from the scarcity of 64-bit operations in the game's executable code, especially when running with a 32-bit machine architecture as a host. Most of these emulators perform most calculations at 32-bit precision and trap the few subroutines that actually make use of 64-bit instructions.

Reality Coprocessor

Main article: Reality Coprocessor

Nintendo 64's graphics and audio duties are performed by the 64-bit SGI coprocessor, named the Reality Coprocessor, or RCP. The RCP is a 62.5 MHz chip split internally into two major components, the Reality Drawing Processor (RDP) and the Reality Signal Processor (RSP). Each area communicates with the other by way of a 128-bit internal data bus that provides 1.0 GB/s of bandwidth. The RSP is a MIPS R4000-based 128-bit integer vector processor. It is programmable through microcode, allowing the chip's functions to be significantly altered by each software title if necessary, to allow for different types of work, precision, and workloads. The RSP performs transform, clipping and lighting calculations, and triangle setup. The Reality Display Processor is primarily the Nintendo 64's pixel rasterizer, and also handles the console's Z-buffer compute.

Instead of a discrete sound processor, the RSP frequently performs audio functions, although the CPU can be tasked with this as well. It can play back most types of audio (dependent on software codecs) including uncompressed PCM, MP3, MIDI, and tracker music. The RSP is theoretically capable of a maximum of 100 channels of PCM at a time, but only in a case where all system resources are devoted to audio. It has a maximum sampling rate of 48 kHz with 16-bit audio. In practice, however, storage limitations caused by the ROM cartridge format limit the audio size and thus quality. Some game titles are designed for higher quality audio when storage expansions are available, as with F-Zero X Expansion Kit.

The RDP performs rasterization, converting images into raster format before output to the display. The RCP also provides the CPU's access to main system memory via a 250 MB/s bus. Unfortunately, this link does not allow direct memory access for the CPU. The RCP, like the CPU, is passively cooled by an aluminum heatspreader that makes contact with a steel heat sink above.

Memory

We use the cartridge almost like normal RAM... So the cartridge technology really saved the day.

— Factor 5

The final major component in the system is the random-access memory, or RAM. Following its design heritage in SGI supercomputing, the Nintendo 64 is one of the first modern consoles to implement a unified memory architecture (UMA), instead of having separate banks of memory for CPU, audio, and video, for example. The RAM itself consists of 4 megabytes of RDRAM, made by Rambus. The RAM is expandable to a total of 8 MB with the Expansion Pak. The RAM has a 9-bit data bus at 500 MHz providing the system with 562.5 MB/s peak bandwidth. Rambus was quite new at the time and offered Nintendo a way to provide a large amount of bandwidth for a relatively low cost. The narrow bus makes board design easier and cheaper than the higher width data buses required for high bandwidth out of slower-clocked RAM types (such as VRAM or EDO DRAM); however, RDRAM, at the time, came with a very high access latency. The combination both complements and challenges game developers. Later models used just a single 4 megabyte RAM chip, earlier models used two 2 megabyte chips.

The Nintendo 64 Game Pak ROM cartridges are so much faster than contemporary CD-ROM drives that data can be streamed in real-time from cartridges as if they are additional RAM, thus maximizing the efficiency of the system's RAM. This was a common practice for developers of many games, such as Nintendo EAD's Super Mario 64 or Factor 5's Indiana Jones and the Infernal Machine.

Video

The system allows for video output in two formats: composite video and S-Video. This is accomplished through the "MULTI OUT" connector on the rear of the system. Although the digital-to-analog converter chip used in early models had such a capability built-in, later editions lacked the pin connections necessary to provide RGB video. In most countries the system came bundled with a composite cable (AKA Stereo AV cable). The composite and S-Video cables are the same proprietary units used with the earlier SNES and later GameCube systems.

Available separately is a RF modulator and switch set (for connection to older televisions) and an official S-Video cable, although the latter was only sold at retail stores in Japan. In the U.S., the official S-Video cable could only be ordered direct from Nintendo of America, and the cable was not officially sold in Europe. In the United Kingdom the console shipped with an RF modulator and switch set, but is still fully compatible with the more modern cables.

The system supports standard-definition resolutions up to 480i (576i for units in the PAL region). Few games make use of this mode, and many of those which do also require use of the Expansion Pak RAM upgrade. The majority of vintage games instead use the system's low-definition 240p (288p for PAL models) modes. A number of games also support a video display ratio of up to 16:9 using either anamorphic widescreen or letterboxing. However, very few games provide options to use this feature, such as these: Banjo-Tooie, Donkey Kong 64, GoldenEye 007, The World Is Not Enough, Jet Force Gemini, Perfect Dark, Starshot: Space Circus Fever, Turok 2: Seeds of Evil, Turok 3: Shadow of Oblivion, Mission Impossible, Hybrid Heaven, and South Park.