PC Engine SuperGrafx

The PC Engine SuperGrafx (PCエンジンスーパーグラフィックス, Pī Shī Enjin SūpāGurafikkusu), also shortened as the SuperGrafx or PC Engine SG, is a video game console by NEC Home Electronics, released exclusively in Japan. It is an upgraded version of the PC Engine.

Originally announced as the PC Engine 2 (PCエンジン2, Pī Shī Enjin Tsū),^[2] the machine was purported to be a true 16-bit system with improved graphics and audio capabilities over the original PC Engine. Expected to be released in 1990, the SuperGrafx was rushed to market, debuting several months earlier in late 1989 with only modest improvements over the original PC Engine.

Only seven games were produced which took advantage of the improved SuperGrafx hardware,^[3] and two of those could be played on a regular PC Engine. However, the SuperGrafx is backwards compatible with all PC Engine software in both, HuCard and CD-ROM² format, bringing the compatible software total up to nearly 700. The system was not widely adopted and is largely seen as a commercial failure.

Hardware

Compared to the PC Engine, the SuperGrafx has four times the amount of working RAM for the main CPU and a second video chip with its own video RAM. Also included is a priority controller chip, which allows the output of both video chips to be combined in various ways. The SuperGrafx has support for two independently scrolling background layers, like the Mega Drive, as opposed to the PC Engine's single layer.

It is a very common misconception^[4] that the extra video hardware capabilities were taxing on the system's CPU, and is often cited as the main reason few games were developed for the system. In reality, despite having the same CPU as the PC Engine, the SuperGrafx is more than capable of keeping up with the new graphics enhancements, as the majority of the workload is handled by the VDPs.

SuperGrafx with Super CD Rom²

One accessory of note was the "Power Console", designed to add a full flight yoke, throttle and keypad to the SuperGrafx, sliding over the entire console. Besides a prototype, no Power Consoles were ever produced.

Since the SuperGrafx was produced and marketed as an upgraded PC Engine model rather than as a new platform, it was backwards compatible with standard PC Engine HuCards in addition to its own. However, SuperGrafx-specific HuCards were expensive compared to standard HuCards, in some cases approaching as much as $110 USD at retail.

The SuperGrafx is also compatible with the CD-ROM² System add-on (via the ROM² Adaptor), as well as the Super CD-ROM² add-on. No CD-ROM² format games were produced that took advantage of the SuperGrafx's added capabilities.

Technical specifications

• CPU: 8-bit HuC6280A, a modified 65SC02 running at 1.79, or 7.16 MHz (switchable by software). Features integrated bankswitching hardware (driving a 21-bit external address bus from a 6502-compatible 16-bit address bus), an integrated general-purpose I/O port, a timer, block transfer instructions, and dedicated move instructions for communicating with the HuC6270A VDC.
• GPU: A multiple graphics processor setup. One 16-bit HuC6260 Video Color Encoder (VCE), two 16-bit HuC6270A Video Display Controllers (VDCs), and one HuC6202 Video Priority Controller. The HuC6270A featured Port-based I/O similar to the TMS99xx VDP family.

Display

• Resolution
  • X (Horizontal) Resolution: variable, maximum of 565 (programmable to 282, 377 or 565 pixels, or as 5.37mhz, 7.159mhz, and 10.76mhz pixel dot clock)^[5] Taking into consideration overscan limitations of CRT televisions at the time, the horizontal resolutions were realistically limited to something a bit less than what the system was actually capable of. Consequently, most game developers limited their games to either 256, 336, or 512 pixels in display width for each of the three modes.^[6]
  • Y (Vertical) Resolution: variable, maximum of 242 (programmable in increments of 1 scanline)
• Color
  • Depth: 9-bit
  • Colors available: 512
  • Colors onscreen: 482 (241 background, 241 sprite)
  • Palettes: 32 (16 for background tiles, 16 for sprites)
  • Colors per palette: 16
• Sprites
  • Simultaneously displayable: 128
  • Sizes: 16×16, 16×32, 16×64, 32×16, 32×32, 32×64
  • Palette: Each sprite can use up to 15 unique colors (one color must be reserved as transparent) via one of the 16 available sprite palettes.
  • Layers: The dual HuC6270A VDCs are capable of displaying 2 sprite layers (1 each). Sprites could be placed either in front of or behind background tiles. Each layer can display 16 sprites or 256 sprite pixels per scanline, giving the combined sprite per scanline limit of 32 sprites or 512 sprite pixels.
• Tiles
  • Size: 8×8
  • Palette: Each background tile can use up to 16 unique colors via one of the 16 available background palettes. The first color entry of each background palette must be the same across all background palettes.
  • Layers: The dual HuC6270A VDCs were capable of displaying 2 background layers (1 each).

Memory

• Work RAM: 32KB
• Video RAM: 128KB (64KB per HuC6270A VDC)

Audio capacity

• Six Wavetable Synthesis audio channels, programmable through the HuC6280A CPU.
• Each channel had a frequency of 111.87 kHz for single cycle of 32 samples (while not in D/A mode) with a bit depth of 5 bits. Each channel also was allotted 20 bytes (32×5 bits) of RAM for sample data.
• The waveforms were programmable so the composers were not limited to the standard selection of waveforms (square, sine, sawtooth, triangle, etc.). But the use of standard waveforms, and semi-standard forms, such as a 25% pulse wave were used fairly often.
• The first two audio channels (1 and 2) were capable of LFO when channel #2 was used to modulate channel #1. In theory, this could also be used to perform an FM operation, though due to other limitations, this was never done (note: LFO, like FM works by modifying an audible waveform (carrier oscillator) with an inaudible waveform (modulator oscillator), but LFO's modulator is subsonic rather than sonic (FM), so LFO will not change the carrier's timbre, just its behavior, and as a result, LFO does not really sound anything like FM.)
• The final two audio channels (5 and 6) were capable of Noise generation.
• Optional software enabled Direct D/A which allows for sampled sound to be streamed into any of the six PSG audio channels. When a channel is in D/A mode the frequency is as fast as the CPU can stream bytes to the port, though in practicality it is limited to 6.99 kHz when using the TIMER interrupt with its smallest loop setting (1023 cpu cycles) or 15.7 kHz using the scanline interrupt.
• There is a method that combines two channels in DDA mode to play back 8-bit, 9-bit, or 10-bit samples.
• The addition of the CD-ROM peripheral adds CD-DA sound, and a single ADPCM channel to the existing sound capabilities of the PC Engine.
• Sound system is often mistakenly called PSG, but this is incorrect. It is Wavetable Synthesis. The fairly common use of standard and semi-standard waveforms is the most likely source of the confusion. But PSG and Wavetable do not generate sound the same way. So, even when they're both making exactly the same tone, there's still something completely different going on "under the hood." The only point at which the term PSG may ever be appropriately used when applied to this sound system is in the ability to use white noise on channels 5 and 6.

Software media

• HuCard: A thin, card-like game media that served as the PC Engine's proprietary software storage format. The SuperGrafx was backwards compatible with all legacy HuCards in addition to its own. The labels on SuperGrafx HuCards were upside-down relative to standard HuCards; A standard HuCard will read upside down on a SuperGrafx, while its own are right-side-up.
• CD-ROM²: The SuperGrafx is compatible with all CD-ROM² System titles, including Super CD-ROM² and Arcade CD-ROM², provided the console is connected to a CD-ROM drive add-on and has the required System Card. No CD-ROM² games were produced specifically for the SuperGrafx.

Input/Output

• HuCard cartridge connector.
• EXT-BUS expansion connector. (for Super CD-ROM², Tennokoe 2, RAU-30, etc.)
• Standard mini-DIN gamepad connector.
• Enhanced I/O port with 8 output and 4 input pins for the unreleased Power Console peripheral.
• 5-pin DIN A/V connector with composite video and stereo audio output only.
• Power adapter jack.
• Compatibility mode (PC-Engine or SuperGrafx) switch on back of unit.

Peripherals

• ROM² Adaptor (RAU-30) - An adapter released in Japan on April 20, 1990^[7] that allows the SuperGrafx unit to be connected into CD-ROM² System's Interface Unit. This was not required for the later Super CD-ROM² System add-on.
• Power Console (PI-PD7)^[8] - An unreleased cockpit-sized controller that attaches onto the SuperGraph unit itself, connecting via the expansion port on the front side. The peripheral would've added numerous control options such as an eight-way joystick, four action buttons, a flight yoke with two triggers (one on each handle), a throttle lever, a jog dial, three mode switches, an LCD panel, an LED indicator, four additional controller ports and a numerical keypad. The Power Console was scheduled to be released on Spring 1990 with a suggested retail price of 59,800 yen, but was never released due to its high production cost and the poor sales of the SuperGrafx itself.^[9][10]

The SuperGrafx is compatible with all standard PC Engine input devices, such as the TurboPad and the Multitap.

Software catalog

Platform specific

All SuperGrafx releases were on the HuCard format.

• 1941: Counter Attack
• Aldynes
• Battle Ace
• Daimakaimura
• Madō King Granzort

Forward compatible (PC-SG)

These HuCards were designed to take advantage of the PC Engine SuperGrafx's enhanced capabilities, but were otherwise forward compatible with standard PC Engine consoles. They featured the PC-SG mark on them.

• Darius Alpha
• Darius Plus

Unreleased

• Forgotten Worlds - Announced only. Eventually released in Super CD-ROM² format.
• Galaxy Force II
• Strider Hiryu - Announced only. Eventually released in Arcade CD-ROM² format.

References

External links

• pcenginefx - Enthusiast-run site for NEC video game consoles.