During the Sega Saturn’s lifecycle there were multiple development kits available to developers starting from the original Sophia Systems that came out before the retail hardware, followed by devkits from both Cross Products (Official) and the Unofficial SN Systems (PSYQ).

Sega Saturn Programming Box (Sophia Systems)

The original Sega Saturn Programming box (or P-Box) became available to developers before the retail release of the Saturn and was the first development kit available for the Saturn ¹.

The Sophia needs to have 2 processors installed to be a working development system but occasionally people sell the systems with only one processor. If only one processor is present it will still boot to dashboard but you won’t be able to run anything.

These were later replaced by the CartDev development kit but the new CartDev also had configuration options to connect to the older P-Box.

The P-Box had a DIP switch to change between the built in CD emulator (which booted from hard drive) to the actual CD drive, so developers could load their game on the built in hard drive instead of burning a CD each time they wanted to test.

The P-Box also has a custom Japanese-only SCSI connection to the developers PC (or SGI Indy) so the developer could send game builds to the system and debug games from the PC interface.

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Cross Products Dev Kit (SNASM2)

Cross Products is a UK based company that specialised in createing development kits of all sort of consoles, most success came with their SEGA mega-drive line of products. So when the SEGA Saturn was announced they jumped on board to build their own development kit known as the Cross Saturn based on their SNASM2 line of development kits.

The Software Development Kit that was provided with these systems were also provided by Cross Products and were under the SNASM2 SDK brand name. This provided all the standard libraries, compilers and other build tools to create Saturn games.

There was an advert in the Uk magazine EDGE issue 21 that took the space theme of the saturn and ran with it:

According the to advert it was a pretty advanced game development kit back in 1995 ²:

SNASM2 can give you the edge! The preferred development system of SEGA Worldwide, SNASM2 Saturn provides full C Source level debugging, C-Structure browse > facility, and local variable windows, along with support for user breakpoint controller in SH2s.

These photos of the Japanese SNASM2 Saturn kit were posted by ausretrogamer on December 26, 2016:

According to an article in issue 23 of the UK Magazine EDGE Cross Products had just been bought by SEGA and were put in charge of supplying the next development kit known as CartDev. There were also responsible for the Mirage CD Emulator and Modified Saturn sold to game development studios ³.

CodeScape put the debugger around the CartDev

A January/February 1997 DevelopMental announcement offered Cross Products’ CodeScape as a $400 upgrade for existing Saturn development systems. It could load existing SNASM COFF files, set breakpoints on accesses within memory ranges or to external peripherals, and operate multiple CartDevs for multiplayer development. Its editor, build, download, and debugger controls lived in one interface ⁴. This describes the advertised tool, not a claim that every CartDev installation used it.

For a reverse engineer, COFF support is the interesting bridge: the debugger expected symbol-bearing development builds, while a retail binary often leaves only the resulting machine code. The announcement also records a CartDev RAM buffer board as an aid to porting a large PC project before shrinking its code and data ⁴.

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Sega CartDev

The CartDev system was a much cheaper alternative to the Sophia P-Box costing just 4,800 USD instead of the 7,475 USD for the P-Box. It was the result of SEGA buying the development studio Cross Products and rebranding their SNASM2 development kit as the Official Sega CartDev. 

There are 2 versions of the CartDev kit:

• Cross CartDev Rev.A
• Cross CartDev Rev.B

The first Revision (Rev A) has an issue with the power supply unit and so was quickly replaced with the latest revision B model, so it is much more common to find the Rev.B model out in the wild ⁵.

The following youtube video shows a CartDev in action:

Connecting CartDev To the old P-Box

The new CartDev development kit needed Saturn hardware to connect to, as the Sophia P-Box was technically Saturn hardware it could also be used with the CartDev development kit. This would have been at least a partial relief for developers who spent thousands of dollars on the first Sega Saturn Development kit, only for it to be replaced by the CartDev not long after.

Connecting CartDev to modified retail Saturn

For developers that didn’t have a Sophia Systems Programming Box there was a much cheaper alternative provided with the CartDev system. Cross Products could modify a retail Sega Saturn console and allow it to connect to the CartDev system.

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Modified Sega Saturn

The Modified Sega Saturn that Cross Products sold to game developers was known as the DevSaturn and can be seen in this sort youtube video:

It cost $700 and it was not able to run burned CDR games without the System Boot Disc so there was no benefit to non-developers for owning the modified unit.

It has a DIP switch on the side to switch between the CD emulator and the actual CD drive inside the Saturn. It also has a connection port on the left hand side of the unit along side a Cross Products Logo. This is where it would connect to the Mirage CD emulator from Cross Products.

You can see the back of the modified Saturn with the cross products CD Switch in a photo taken by stevejigga and posted on the AssemblerGames forum:

Notice the VCD port, this is not for the Video Compact Disc feature of the Sega Saturn but instead used for Virtual CD emulators such as the Mirage which was a hard-drive that emulated the functionality of loading a CD, much quicker than actually burning a physical CD! ⁵

The modification to be able to use the CD emulator, along with the region switcher is the only modifications made to most of the the retail Saturn units known as the MS100 model. However there was an additional variant with a MIDI interface to connect to the Sega Sound Tools if you bought the MC100 model ⁵.

The official price list from Cross Products put the Modified Saturn by itself at a price of £500 which are simply described as:

A production Saturn fitted with shielded NMI cables and CD switch (VCD)

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Address Checker Hardware by SI Electronics

Codemasters showed this Sega Saturn Address Checker on November 8, 2019.

In order to make sure your game doesn’t violate the Sega Memory usage guide this piece of hardware would allow running your game with real-time checking of the memory addresses used.

If the game accessed memory in certain restricted regions this machine would send an error message to an attached PC. Apart from that functionality it is exactly the same as a retail Saturn console (including the need for System Disc to run CD-Rs).

This machine would likely be used by Sega themselves to check if games can be given the go-ahead to be produced, otherwise they would be failed and given back to the developer to fix the memory issues.

SegaRetro has photographs of an LED-equipped Address Checker, a useful visual companion to the catalogue’s description.

What an address error left behind

The Address Checker reference manual divides memory into more than simply “allowed” and “forbidden.” Unallocated space rejects reads and writes. For parts of VDP1, SCSP, and SMPC with mixed used and unused register bits, a read can be allowed while writing a 1 to a free bit triggers detection. Other unused register areas reject writes outright ⁶. This is why a bit mask can matter as much as the address in a hardware test.

On the attached PC, the BM.EXE monitor could stop at a trigger and dump recent bus cycles with TDMP. Each record labels the address and data, access space, and bus master - master SH-2, slave SH-2, or SCU - along with a marker for the triggering cycle ⁷. That makes an error a trail of who touched what, rather than just a red light. The operation manual even demonstrates redirecting a trace range to a DOS file for closer inspection ⁸.

What the portable SS Checker could tell you

The reconstructed DTS hardware catalogue describes a lower-cost Saturn SS Checker V1.00 intended for quick illegal-address tests ⁹. Its LEDs corresponded to memory regions: LED 1, for example, meant an illegal ROM-area access. It ran without a host PC, like a production Saturn, but did not report the exact address, program counter, or whether the operation was a read or write. A lit LED could narrow the search; the fuller Address Checker was still needed to locate the instruction. The catalogue says the SS Checker was not a replacement for that larger system.

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Sega Saturn Boot Disc

Similar to the Dreamcast’s System Disc 2, this is a disc that allows any retail Sega Saturn to play developer written CD-Rs without any Saturn modding required.

This is very useful for developers as they could burn CD-Rs and pass them off to the testing team that just need the system disc and the burned CD-R ¹⁰.

There are two versions available, one in red and the other in black, one can only be used for Sega first party titles as it was only used in-house at Sega. The other was given to 3rd party developers and only boots 4rd party games.

Note that when using the system disc it will go back to the dashboard and disable the security check, so just pop the CD-R disc into the drive and it should boot as normal.

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Mirage CD Emulator

The Mirage CD Emulator was developed by Cross Products and sold to development studios to save time and discs by emulating the use of a physical drive.

It cost $3000.00 to buy directly from SEGA and contained a 1gb hard drive inside, allowing for a couple of games to be stored on it.

Similar to mounting an ISO on a PC, although instead of ISO the Mirage used a custom format that needed to be created with special development kit tools.

This allowed developers to simulate errors with the disc to make sure their game was as robust as possible.

For more information about the Mirage please check out this excellent page on SegaRetro: MIRAGE Universal CD Emulator

The Mirage wasn’t the only way to mount discs for the development system, there was also a Virtual CD emulator available for the P-box. This allowed much more discs to be mounted as it could use the entire PC hard drive as storage.

Virtual CD emulation workflow

Sega’s Virtual CD (VCD) system was a separate route to testing a disc build on target hardware. Its manual starts with a disc script, then offers two preparation modes before VCDEMU.EXE runs the result ¹¹. The preserved VCDTOOLS package includes the programs and actual .SCR, .PVD, and .RTI examples for Sega and CartDev setups ¹².

Mode	Preparation	What the emulator reads
Direct DOS file access	VCDPRE.EXE maps script entries to host-file locations	Host files and generated lookup data
Real-time emulation	VCDBUILD.EXE builds an image and table of contents	Prepared CD image and TOC data

The distinction affected iteration. Sega’s manual says that changing a file’s size requires rebuilding the configuration, even in direct-access mode. In real-time mode the CD image must be updated after a content change. The manual also describes VCDUTL.EXE for partial image updates ¹¹. Its later supplement adds VCDEMU buffer options to make unusually large numbers of tracks or indexes fit within a PC’s conventional memory ¹³.

This is a period developer workflow, not an instruction to run the DOS executables on a modern machine. For an example of how the script maps compiled files onto a Saturn disc, see compiling an official sample.

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Hitachi E7000 PC Debug Unit (ICE)

The Hitachi E7000 PC Debug Unit is an In Circuit Emulator or ICE for short, it connects to the Sophia (P-Box) or the Address Checker hardware and also the developers PC.

This was used by developers to debug their games and it acted as a full SH-2 cpu. It was not cheap as one unit cost $15,000.00 USD including all wires and documentation, so not all developers could have one of these units.

You can use the ipi executable included with the hitachi development kit to connect to it as shown in the video below:

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Hardware for Designers

Sega recommended Macintosh for sound designers or 2D Artists, and SGI INDY or INDIGO2 machines for 3D work. Sega also released a couple of hardware attachments for Macintosh systems specifically for these designers.

Sound Target Box by Sophia Systems

For sound designers a Sound Box could be purchased for $4,800.00 from SEGA and connected to the sound designers Macintosh system.

This was the first sound development hardware available for the SEGA Saturn and was later replaced by a model of the CartDev development kit which has a MIDI port that also connected to the Macintosh based SEGA Sound Tools.

Graphics Target Box by Sophia Systems

For Graphics Designers a Graphics Box developed by Sophia Systems can be purchased from Sega. This image was from Chris M Covell¹⁴ and you can check out his excellent site here: Sega Saturn Graphics Box.

As this is similar to the Sound Box it is likely that this also got replaced by the CartDev development kit, but it is unlikely it would need a special model as there would be no need for an additional connectivity options as the SCSI port should be able to handle any graphics being sent between development PC and graphics development kit.

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Overall Cost of Development Kits

Sega of America’s June 1996 Saturn Development System order form gives a dated snapshot of what a licensed studio could order. These are separate configurations and accessories, not items every developer had to buy together ¹⁵.

The form lists these selected US prices and dependencies:

Item	June 1996 price	What the order form includes or requires
CartDev kit (SN310)	$4,800	Modified Saturn, CartDev, SNASM2 software and manuals; requires separate CD emulation
Programming Target Box (ST-4001)	$7,475	Target Box/S with CD drive; requires an additional SH-2 CPU board or emulator
Saturn Dev System I (ST-1000-01)	$30,575	Target Box, Hitachi E7000PC ICE, software and manuals, and VCD board
Modified Saturn (ST-MSAT-00)	$700	Production US Saturn with NMI and VCD interfaces for CartDev
Mirage CD emulation system (SN350)	$3,000	Host-PC attachment with a 1 GB hard drive and VCD-tool compatibility
Virtual-CD emulator kit (ST-RT-V3VCD)	$8,100	PC board, cable, and notes; a different offering from Mirage
Hitachi E7000PC kit (ST-E7000PC)	$15,000	E7000PC, SH-2 pod, PC interface, cables, documentation, and software

The order form makes an important distinction: the $4,800 CartDev bundle supplied the modified Saturn but still called for separate CD emulation. The $30,575 system already bundled the Target Box, ICE, and VCD board, so adding their individual prices would double-count equipment. These are historical list prices; the form says they were subject to change ¹⁵.

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In this side by side example of the Sega Saturn and Nintendo 64 you can see which one developers preferred in terms of cost:

Comparing development hardware costs #SegaSaturn vs #Nintendo64 pic.twitter.com/v5GOhLGFXg

— Shane Battye 🎮 (@shanebattye) July 11, 2019

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3rd Party Development kits

Although the Cross Products development kit was initially a 3rd party development kit it was included on this page as it became the official CartDev development kit. However there was also another competing 3rd party development kit by Sony of all people.. well technically a company that got bought by Sony: Sn Systems & Psygnosis. It was called the Psy-Q Saturn development kit and it was part of a cross platform suite of development kits.

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References