DreamShell: Operating System for the Sega Dreamcast | Hacker News Reader

DreamShell: Operating System for the Sega Dreamcast

github.com

99 pointsskibz14 comments

FTA:

"DreamShell

The Dreamshell is the operating system for the Sega Dreamcast based on the KallistiOS[0] kernel. It has a dynamic loadable modular system and interface for creating applications with XML UI and both C/C++ and Lua script on. You can see examples in ready-made applications and modules, drivers for various devices, formats and interfaces. Examples for audio and video decoding, compression, packaging, binding, network, emulation, scripts and more. From hardcore low-level assembler to high-level applications. There are also large subproject is the ISO Loader, which contains emulation of BIOS system calls, CDDA playback and VMU, also it can hooking interrupts for various SDKs and more."

"KallistiOS is an unofficial development kit for the SEGA Dreamcast game console with some support for the NAOMI and NAOMI 2 arcade boards.

KOS was developed from scratch over the internet by a group of free software developers and has no relation to the official Sega Katana or Microsoft Windows CE Dreamcast development kits. This has allowed it to fuel a thriving Dreamcast homebrew scene, powering many commercial releases for the platform over the years. It supports a significant portion of the Dreamcast's hardware capabilities and a wide variety of peripherals, accessories, and add-ons for the console, including custom hardware modifications that have been created by the scene.

Despite the console's age, KOS offers an extremely modern, programmer-friendly development environment. Using the latest GCC toolchain, it supports the entirety of C17 and C++20 including their standard libraries, along with support for portions of C23, C++23, Objective-C, and various POSIX APIs. Additionally, KOS-ports offers a rich set of add-on libraries such as SDL, OpenGL, OpenAL, and Lua for the platform."[0]

[0] https://github.com/KallistiOS/KallistiOS

For those that might not be aware, the Dreamcast can read regular CDs but also GD-ROMs, a 1GB density format (though not as high density as DVD). The only other system I know that can read them is Sega’s NAOMI arcade (and the colab Triforce) hardware, which would read the entire disc into RAM and then not used again during gameplay.

I'm sure you know but this is a bt backwards. GD-ROMs are the native format for games because of the higher density. The Dreamcast can also play music CDs, but CD really comes into play for playing game "backups". The original content was read from the GD-ROM disks, unnecessary bits were removed, some stuff would be compressed, etc to get down to the around 800K that you could stuff onto a regular CD.

I just picked up a Dreamcast before Christmas as part of a retro console spree and the modding scene is very active around it. There is the GD-emu that can replace the GD-ROM drive and store your library of games on a memory card, replacement power supplies, SDCard attachments for the console's serial port, dual-bios mods (that Dreamshell can reprogram in place!), replacement cases, and the list goes on. There is an active homebrew scene as well with some high quality games still being released.

I myself want to get away from the GD-ROM for playing games as that will eventually become problematic. The GD-emu swaps out the GD-Rom but I want to keep it in the unit just because. So over the last couple days I've ordered up the parts that will add compact flash capability to the console by piggybacking on to the Dreamcast's IDE bus interface to the GD-ROM (compact flash is basically an IDE interface). But compact flash storage cards are expensive, so I'm also getting a compact flash to SD-Card adapter. This isn't new ground so far, but I think I can do this as a stealth mod and do it all within the GD-ROM enclosure.

Beware that if you attempt to use an SDXC card that a lot of the really cheap made in China CF to SD adapters do not support capacities above 32GB (SDHC). I'm not affiliated with the site, but from experience modding iPods I can recommend the iFlash CF to SD adapter as one I would trust [0].

[0] https://www.iflash.xyz/store/sdcf-adapter/

Thanks! I'll keep an eye out for that but my really cheap (8$ CAD) made in China CF to SD adapter claims it supports 4TB [0]. We'll see!

[0] https://www.aliexpress.com/item/1005006102185399.html

Sega’s market advantage was that the hardware R&D was mostly paid for by their very successful arcade business (they still have major success here) and they made reduced costs versions of arcade hardware and sold them as home consoles.

It was this hardware expertise that lead to their acquisition by Sammy, a company that makes Japanese slot machines. They also valued the better public image a game company has, and adopted Sega’s name.

Bad news on the arcade front:

https://www.polygon.com/22906391/sega-japan-arcades-sold-his...

Sega is leaving Japanese arcades behind. The company announced it is selling its remaining arcades to a company called Genda, Inc. (also known as GiGO), and leaving the coin-op business, where it first made a name for itself, for good.

DreamShell supported SD card on serial port (bit-bang SPI) and IDE HDD/CF on G1 port (GD-ROM uses the same).

> also GD-ROMs, a 1GB density format (though not as high density as DVD)

GD-ROM seems to be a density doubling setup... A CD-ROM drive is run with the motor at 1x and the optics at 2x (all the way up to 12x/24x, IIRC). There must also be some magic for the TOC and what not, and there's some space reserved at the beginning of the disc to have warning audio so you don't try to play it in a regular cd player. (Games with less data could have more stuff accessible for regular drives, but I don't remember if that was actually done though, or if I'm misremembering things from earlier cd consoles)

Yeah, that’s my understanding. Sega CD and PlayStation both used ISO-9660 based CD-ROMs, frequently with CDDA tracks. Occasionally these would include warning audio as well, however CD players at the time didn’t know to skip the DATA track 1.

Some Japanese dreamcast games had anime content and character art.

Always thought that was cool

Also you can see some videos how it works: https://www.youtube.com/SWAT-DC/videos

Thank you for your attention, I am very pleased to see this!

Additional links of DreamShell project:

Website: http://www.dc-swat.ru Forum: http://www.dc-swat.ru/forum/ Discord: https://discord.gg/UrvKwwU Youtube: https://www.youtube.com/SWAT-DC/videos

They have some Screenshots on their website: http://www.dc-swat.ru/

That's pretty damn cool

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