Sega NAOMI update: DIMM board and IDE adapter arrived!
One of the major differences between NAOMI and consumer Dreamcast hardware is that loading your game is a more open-ended affair.
While the Dreamcast worked exclusively off a internal GD-ROM drive, NAOMI initially took ROM cartridges. This was more expensive, but cut down sharply on load times and crucially eliminated a major potential failure point: A very important decision for an arcade-centric design, which would be subject to much longer runtime and much more abuse than a mass market game console.
However, Game developers would occasionally want to make a game that was too big to feasibly fit on a expensive ROM board, and operators would occasionally want something more economical. This mandated an addition to make NAOMI accept the same GD-ROM media.
Enter the DIMM board and NAOMI GD-ROM system.
As I alluded to earlier, optical media tends to be a major failure point. The more a disc drive gets worked, the more a motor, a sensor, the laser, or one of the other sensitive mechanical components is likely to fail. The less it does, the better in a environment where long runtime and minimal service are to be expected.
When SEGA’s engineers designed the DIMM board, the cartridge that interfaces NAOMI to a GD-ROM drive, they did something pretty clever. As the name implies, the DIMM board integrated standard DIMM RAM modules for use as a cache! Instead of directly accessing the disc whenever it needs data like a Dreamcast would, the NAOMI GD-ROM system copies all the data off the disc onto the RAM disk on startup. This sharply minimizes the amount of use the drive receives, as the system can just retrieve the data it requires off the DIMM board’s RAM disk.
For reasons of further simplifying things, I’m doing something sneaky: Since the GD-ROM drive connects to the DIMM board over a relatively standard IDE connection, it’s possible to replace the GD-ROM drive with a CompactFlash memory card using a custom adapter board. This requires certain firmware version requirements to be met on both the DIMM board and the base console.
Another popular option is to use the later NetDIMM board, which has a network interface, to boot games off a network server. I wanted something lower maintenance, however.
