SMPS

From Sega Retro

SMPS (Sample Music Playback System) is the common name of a family of audio playback engines (or "drivers") and storage formats used by various Sega consoles (including the Sega Mega Drive, Sega Mega-CD, Sega 32X, Sega Master System, Sega Game Gear, and Sega Pico). "SMPS" is thought to be a colloquial term - there is no evidence to suggest this was the naming scheme of any official drivers, but is the most widely accepted name for the system.

Like other sound drivers, SMPS was designed as a means of processing audio information, allowing a console's CPU to communicate with sound chips on the board and create audible sound (i.e. "driving" the sound). It is usually associated with first-party Japanese Mega Drive games (where it was most predominantly used) - analogous to Sega of America's use of the GEMS driver, and began appearing in games from the late 1980s until the aforementioned consoles bowed out of the market.

By sharing drivers between games, developers could create tools to quickly produce audio, and it allows for music and sound effects to be more easily ported between games.

Variants

Mega Drive, Mega-CD and 32X

Mega Drive (and by extension, Mega-CD and 32X) developers had a choice of which processor to run SMPS on; the 16-bit 68000, or the 8-bit Z80. The driver variants are known as SMPS 68000 and SMPS Z80 respectively. These tap into the consoles' YM2612 and SN76489 chips, with the Mega-CD and 32X variants tapping into each of the add-on's additional sound hardware.

Some developers, such as Treasure, chose to modify the driver, effectively making their own variants. Individual games such as Ristar also have their own modified drivers.

Games which use SMPS 68000

Mega Drive
Mega-CD
32X

Games which use SMPS Z80

Mega Drive
Mega-CD
32X

Source code

On June 16, 2020, the source code to both SMPS 68000 and SMPS Z80 was found and released by Hidden Palace, along with several internal documents relating to the Mega Drive's sound hardware.[1] The versions of the two drivers appear to be SMPS 68000 Type 1b and SMPS Z80 Type 1 FM respectively. Both versions of the drivers date from September 1991, according to the date written on the labels of both floppy disks containing the two drivers' source codes.

Download.svg Download SMPS 68000 source code
File: SMPS-68000_source_code.zip (231 kB) (info)
Download.svg Download SMPS Z80 source code
File: SMPS-Z80_source_code.zip (258 kB) (info)

Mega-CD

SMPS-PCM is a variant of SMPS 68000 designed to work on the Mega-CD's second 68000 processor, giving it access to the system's RF5C164 PCM chip.

SMPS drivers designed for the Mega Drive can also be used in conjunction with Mega-CD games.

Master System and Game Gear

SMPS drivers designed to work on the Z80 processors of the Master System and Game Gear were also produced. These tap into the two consoles' SN76489 chip.

Pico

SMPS-Pico is a variant of SMPS 68000 designed to work on the Pico's 68000 processor. It taps into the system's SN76489 chip and the µPD7759 ADPCM chip.

Source code

The source code to SMPS-Pico was released on the AssemblerGames forum some time around 2016.

Download.svg Download Sega Pico Dev Tools
File: SEGA_Pico_dev_tools.zip (625 kB) (info)

Naming

The "true" name of SMPS has been a subject of debate for many years. Analysis of the source code reveals various possible names:

Name Usage
Sound Appears frequently in documentation (m5_edit.jxw, ver11.doc, etc.). In the source code, this is the name of the label that marks the driver's entry point (m5cnt13.src, mdcnt11.asm).
Sound-Sorce Appears in the header at the top of SMPS Z80's source code files. Included with the source code is a sed script that replaces the instances of this name with a parameter that is labelled "game name". This script was seemingly used on a handful of files, replacing "Sound-Sorce" with "MODEM_BOOT_ROM" and "DICK_TRACY".
Sound-Source Appears in the header at the top of SMPS 68000's and SMPS-Pico's source code files. It is also the name used by some developers who had used SMPS back in the 90s.[2][3][4] Included with the source code is a sed script that replaces the instances of this name with a parameter that is labelled "game name".
Sound-Sample Written on the labels for the SMPS 68000 and SMPS Z80 source code's floppy disks. The SMPS 68000 source code has a batch script (fmk.bat) that uses the aforementioned sed script to replace "Sound-Source" with "Sound-Sample".
EASYSND The name of the ZIP file that holds another ZIP file which contains the SMPS-Pico source code.
PICOSND The name of the ZIP file which contains the SMPS-Pico source code. Also appears in various filenames and build scripts.
The PICO sound driver Used by SMPS-Pico's GENERIC.MAK and PICOSND.MAK files.

Developers

These are the names of several developers that appear in the SMPS source code:

Name Role Source
Tokuhiko Uwabo Maintainer of SMPS Z80. The header of each source code file. Also mentioned by his Japanese name in the "m5_bord.jxw" document.
Hiroshi Kubota Maintainer of SMPS 68000. The header of each source code file. Also mentioned by his Japanese name in the "readme.txt" document.
"M.Nagao" (presumably Masayuki Nagao) Maintainer of SMPS-Pico. The header of each source code file.
Ken Chao "Cleaned-up" the SMPS-Pico source code for use by Western developers. The "README.1ST" document.

Technical details

Tools

External links

References

  1. ↑ https://hiddenpalace.org/News/Sega_of_Japan_Sound_Documents_and_Source_Code
  2. ↑ https://web.archive.org/web/20191006015702/https://twitter.com/Hikoshi_H/status/1180661206253596672
  3. ↑ https://web.archive.org/web/20190920174036/https://twitter.com/Hikoshi_H/status/1169707879164608513
  4. ↑ https://web.archive.org/web/20200719143541/https://twitter.com/Mazin__/status/105869176442331136
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