Exploring The Sega Saturn’s Wacky Architecture

March 28, 2024 by Maya Posch 44 Comments

Sega Saturn mainboard with main components labelled. More RAM is found on the bottom, as well. (Credit: Rodrigo Copetti)

In the annals of game console history, the Sega Saturn is probably the most convoluted system of all time, even giving the Playstation 3 a run for its rings. Also known as the system on which Sega beached itself before its Dreamcast swansong, it featured an incredible four CPUs, two video processors, multiple levels and types of RAM, all pushed onto game studios with virtually no software tools or plan how to use the thing. An introduction to this console’s architecture is provided by [Rodrigo Copetti], which gives a good idea of the harrowing task of developing for this system.

Launched in Japan in 1994 and North America and Europe in 1995, it featured a double-speed CD-ROM drive, Hitachi’s zippy new SH-2 CPU (times two) and some 3D processing grunt that was intended to let it compete with Sony’s Playstation. The video and sound solutions were all proprietary to Sega, with the two video processors (VDP1 & 2) handling parts of the rendering process which complicated its use for 3D tasks, along with its use of quadrilaterals instead of triangles as with the Playstation and Nintendo 64.

Although a lot of performance could be extracted from the Saturn’s idiosyncratic architecture, its high price and ultimately the competition with the Sony Playstation and the 1996 release of the Nintendo 64 would spell the end for the Saturn. Although the Dreamcast did not repeat the Saturn’s mistakes, it seems one commercial failure was enough to ruin Sega’s chances as a hardware developer.

If You Thought Sega Only Made Electronic Games, Think Again

March 1, 2024 by Jenny List 4 Comments

Most of us associate the name Sega with their iconic console gaming systems from the 1980s and 1990s, and those of us who maintain an interest in arcade games will be familiar with their many cabinet-based commercial offerings. But the company’s history in its various entities stretches back as far as the 1950s in the world of slot machines and eventually electromechanical arcade games. [Arcade Archive] is starting to tell the take of how one of those games is being restored, it’s a mid-1960s version of Gun Fight, at the Retro Collective museum in Stroud, UK.

The game is a table-style end-to-end machine, with the two players facing each other with a pair of diminutive cowboys over a game field composed of Wild West scenery. The whole thing is very dirty indeed, so a substantial part of the video is devoted to their carefully dismantling and cleaning the various parts.

This is the first video in what will become a series, but it still gives a significant look into the electromechanical underpinnings of the machine. It’s beautifully designed and made, with all parts carefully labelled and laid out with color-coded wiring for easy servicing. For those of us who grew up with electronic versions of Sega Gun Fight, it’s a fascinating glimpse of a previous generation of gaming, which we’re looking forward to seeing more of.

This is a faithful restoration of an important Sega game, but it’s not the first time we’ve featured old Sega arcade hardware.

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Sega’s AI Computer Embraces The Artificial Intelligence Revolution

February 4, 2024 by Maya Posch 6 Comments

Recently a little-known Sega computer system called the Sega AI Computer was discovered for sale in Japan, including a lot of the accompanying software. Although this may not really raise eyebrows, what’s interesting is that this was Sega’s 1986 attempt to cash in on Artificial Intelligence (AI) hype, with a home computer that could handle natural language. Based on the available software and documentation, it looked to be mostly targeted at younger children, with plans to launch it in the US later on, but ultimately it was quietly shelved by the end of the 1980s.

Part of the Sega AI Computer's mainboard, with the V20 MPU and ROMs. — Part of the Sega AI Computer’s mainboard, with the V20 MPU and ROMs.

The computer system itself is based around the NEC v20 8088-compatible MPU with 128 kB of RAM and a total of 512 kB of ROM, across multiple chips. The latter contains not only the character set, but also a speech table for the text to speech functionality and the Prolog-based operating system ROM. It is this Prolog-based environment which enables the ‘AI’ functionality. For example, the ‘diary’ application will ask the user a few questions about their day, and writes a grammatically correct diary entry for that day based on the responses.

On the system’s touch panel overlays can be used through cartridge or tape-based application to make it easy for children to interact with the system, or a full-sized keyboard can be used instead. All together, 14 tapes and 26 cartridges (‘my cards’) had their contents dumped, along with the contents of every single ROM in the system. The manual and any further documentation and advertising material that came with the system were scanned in, which you can peruse while you boot up your very own Sega AI Computer in MAME. Mind that the MAME system is still a work in progress, so bugs are to be expected. Even so, this is a rare glimpse at one of those aspirational systems that never made it out of the 1980s.

Can An 8-Bit Light Gun Work On A Modern TV?

October 17, 2023 by Jenny List 55 Comments

It’s an accepted part of retro gaming lore, that 8-bit consoles perform best when used with an original CRT TV. One of the reason for this is usually cited as being because the frame buffer and scaler circuit necessary for driving an LCD panel induces a delay not present on the original, and in particular this makes playing games which relied on a light gun impossible to play. It’s a subject [Nicole Branagan] takes a look at, and asks whether there are any ways to use a classic light gun with a modern TV.

Along the way we’re treated to an in-depth look at the tech behind light gun games, how the gun contained a photodiode which on the NES was triggered by the brief showing of a frame with a white square where the target would sit, and on the Sega consoles by a white screen with an on-board timer counting the screen position at which the gun was aimed.

The conclusion is that the delay means you won’t be playing Duck Hunt or Hogan’s Alley on your 4K TV, but interestingly, all is not lost. There are modified versions of the games that take account of the delay, or an interesting lightgun emulator using a WiiMote. We’d be happy at playing either way, just as long as we can take pot-shots at the annoying Duck Hunt dog.

Light gun image: Evan-Amos, Public domain.

A Cycle-Accurate Sega Genesis With FPGA

August 4, 2023 by Bryan Cockfield 17 Comments

The Field-Programmable Gate Array (FPGA) is a powerful tool that is becoming more common across all kinds of different projects. They are effectively programmable hardware devices, capable of creating specific digital circuits and custom logic for a wide range of applications and can be much more versatile and powerful than a generic microcontroller. While they’re often used for rapid prototyping, they can also recreate specific integrated circuits, and are especially useful for retrocomputing. [nukeykt] has been developing a Sega Genesis clone using them, with some impressive results.

The Sega Genesis (or Mega Drive) was based around the fairly common Motorola 68000 processor, but this wasn’t the only processor in the console. There were a number of coprocessors including a Z80 and several chips from Yamaha to process audio. This project reproduces a number of these chips which are cycle-accurate using Verilog. The chips were recreated using images of de-capped original hardware, and although it doesn’t cover every chip from every version of the Genesis yet, it does have a version of the 68000, a Z80, and the combined Yamaha processor working and capable of playing plenty of games.

The project is still ongoing and eventually hopes to recreate the rest of the chipset using FPGAs. There’s also ongoing testing of the currently working chips, as some of them do still have a few bugs to work out. If you prefer to take a more purist approach to recreating 90s consoles, though, we recently featured a project which reproduced a Genesis development kit using original hardware.

Thanks to [Anonymous] for the tip!

DOOM Ported To Sega Naomi Arcade Hardware

June 17, 2022 by Lewin Day 8 Comments

Porting DOOM to new hardware and software platforms is a fun pastime for many in the hacker scene. [DragonMinded] noticed that nobody had ported the game to the Sega Naomi arcade hardware, and set about doing so herself.

The port builds on work by [Kristoffer Andersen] who built a framebuffer port of DOOM previously. It’s available pre-compiled, complete with the shareware WAD for those eager to load it up on their own Naomi arcade cabinets.

Unlike some limited ports that only give the appearance of a functional version of DOOM, this port is remarkably complete. Loading, saving, and options menus are all present and accounted for, as well as directional sound and even WAD auto-discovery. With that said, there’s only 32 KB of space for save games on the Naomi hardware, so keep that in mind if you find yourself playing regularly.

We love a good DOOM port, whether it’s on an arcade machine, an old forgotten Apple OS, or even a UFI module.

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Mortal Kombat ROM Hack Kontinues Arcade Legacy

March 3, 2022 by Drew Littrell 8 Comments

September 13th 1993, colloquially known as Mortal Monday, became as dividing line in the battle for 16-bit supremacy. The mega popular arcade game Mortal Kombat was ported to Super Nintendo and Sega Genesis consoles, and every fanboy and fangirl had an opinion on which version truly brought the hits. The Super Nintendo version opted to remove the blood and gore in an attempt to preserve the company’s family-friendly image. While the Sega Genesis merely locked the game’s more violent content behind a cheat code that so many fans learned by heart, ABACABB. Nintendo’s decision to censor Mortal Kombat on their console pushed public opinion in favor of the Sega Genesis version being superior, though it was clear that corners were cut in order to squeeze it onto a cartridge. Recently a group of developers led by [Paulo] sought to restore the Genesis version to its full potential with a ROM hack they’re calling Mortal Kombat Arcade Edition.

Mortal Kombat Arcade Edition is the sort of ROM hack where every facet of the game has been retouched. All sorts of sound effects and animations that were omitted in the 1993 translation to the Genesis have now been restored in higher quality. Every fighter’s look was remastered to more closely match the arcade presentation complete with move timing tweaks. Secret characters like Reptile, Noob Saibot, and Ermac are all playable, plus all the character bios from the arcade game’s attract mode make an appearance. An SRAM save feature was implemented in order to save high scores, and for an additional dose of authenticity there’s even a “DIP switch” configuration screen where you can set it to free play.

This ROM hack comes as an IPS patch that can be applied to a legitimate dump of the user’s Sega Genesis or Mega Drive cartridge. The site hosting the Mortal Kombat Arcade Edition patch features an online IPS patching tool called Rom Patcher JS that makes the patching process more convenient for those attached to their browser. The patched ROM can then be enjoyed in the user’s favorite emulator of choice, though running it on original hardware via a ROM cart is also possible (even encouraged). Considering the limitations of the Sega Genesis’ color palette the revamped look of Mortal Kombat Arcade Edition is all the more impressive. It just goes to show you that Genesis still does!

Not ready to FINISH HIM? Check out this countertop arcade build featuring some Mortal Kombat II art, or marvel at the incredible effort that went into creating the Knights of the Round ROM hack known as Warlock’s Tower.

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