Broadband adapter

A black Dreamcast broadband adapter

The Dreamcast Broadband Adapter (HIT-400, sometimes HIT-401; HIT-401 is written on the Japanese box, but HIT-400 is on the peripheral's underside sticker), often abbreviated BBA, is a 10/100mbit network adapter for the Dreamcast based on the Realtek 8139C chip. It connects to the G2 bus in place of the modem, and it was released in Japan and in the United States. Despite not seeing a release in PAL regions, some PAL game software is actually compatible with it, such as Toy Racer and Phantasy Star Online. It is a different piece of hardware than the Dreamcast LAN Adapter.

Software Support

Due to their release towards the end of the Dreamcast's official lifespan, broadband adapters are somewhat uncommon peripherals and are only supported by a handful of games (see https://www.dreamcastlive.net/games for a list). They are also useful for linking to a computer for programming and debugging software (via dcload-ip), as well as dumping GD-ROMs (via httpd-ack).

In Japan, the Dreamcast Karaoke Unit could also access the DreamKara service by way of the Broadband Adapter.

Software made using the open-source KallistiOS development environment has access to a broadband adapter driver, as well.

Regional Differences

The only major difference between the Japanese and North American releases was the packaging, as they had different boxes and manuals, and the Japanese boxes also included the Broadband Passport web browser.

Hardware-wise, all broadband adapters are functionally identical (except MAC addresses, as those are meant to be unique to each device) and are not region-locked in any way. In many cases, they even have the same FCC sticker on the bottom of each unit irrespective of the region in which they were sold, although some have a sticker without the FCC logo on them. It appears that those lacking the FCC logo were likely just built before Sega Enterprises became Sega Corporation in November 2000, as they state "Sega Enterprises" instead of "Sega Corporation."

Availability

Broadband Adapters were made in both black and white colors, although the black models were only available via online order from CSI in Japan. Fewer than 2000 black adapters were made due to low demand during the window of opportunity to pre-order them (December 1, 2001 to December 28, 2001), and they cost 8,800 yen (the same price as the white adapters). Also, an R7 Limited Edition console + broadband adapter bundle was sold by CSI for a limited time, however it is not clear if these consoles were sold with black adapters. Contrary to popular belief, in Japan broadband adapters were only sold by CSI, not by Sega themselves. In the US, however, they could be bought in stores or from Sega's online store for $60.

NOTICE: Due to the lack of exact production numbers, the below estimates are determined by a technique known as "Fermi estimation," which uses available data to estimate order of magnitude rather than calculate perfectly accurate numbers.

Though there is no direct source for the exact number of broadband adapters produced, it is actually possible to estimate how many there are due to the way in which MAC addresses work: Each MAC address consists of 6 bytes AA:BB:CC:DD:EE:FF, with the leading bytes all 00:d0:f1 (the MAC address range owned by SEGA). The next 3 bytes are unique per-device, and it appears that all broadband adapters have '02' or '03' in byte 'DD'. Dreamcast LAN Adapters appear to share the '02' byte. Since 2 bytes hold 65,536 values, this means that within each '02' and '03' MAC address group there are 65,536 possible devices. As it is currently unknown if there are '00' or '01' groups, this means we can estimate that there are potentially 2 groups of 65,536 adapters, or a maximum of 131,072 total BBAs and LAN adapters produced.

We can actually take this estimate further: if the networking adapters are assumed produced in sequential MAC address order, the author of this sentence owns a LAN adapter whose address would suggest something like 4800 LAN adapters were produced. Black broadband adapters, which were among the last produced in 2001, have addresses suggesting around 24,000 devices in group '03'. By the presence of group '03', group '02' was likely full, which would mean a more specific total of roughly 90,000 networking adapters (~4800 LAN adapters, <2000 black BBAs, and ~83,000 white BBAs).

Hardware

The broadband adapter layout is rather simple, being comprised of a very common and inexpensive Realtek RTL8139C 10/100mbps PCI ethernet controller and a custom, SEGA-branded G2-to-PCI bridge chip (often referred to as "GAPS" due to containing the identification string "GAPSPCI_BRIDGE_2"), plus additional supporting circuitry such as a Pulse H0011 isolation transformer, 25MHz crystal oscillator, etc.

Due to the various hardware security measures in place, the GAPS PCI bridge chip has proven very difficult to reverse-engineer, stifling several efforts to make "clone" BBAs over the years. The difficulty in programming the chip has also resulted in incorrect implementations in all known open-source drivers, leading to significantly reduced performance (something like 24Mbps when the chip is actually capable of the full 100Mbps) and inconsistent open-source documentation, motivating a months-long effort by the author of this sentence to better understand the hardware and completely overhaul dcload-ip (Note: still ongoing--this bridge chip is insane).

Of note, it is not likely that the bridge chip itself would be useful in designing arbitrary PCI peripherals for the Dreamcast; certain security measures appear to be essentially "hardcoded" into the hardware for the RTL8139C. The PCI side may also only run at 25MHz, as the bridge chip does not appear to do any intermediary frequency conversion to PCI's conventional 33 or 66 MHz. The RTL8139C can handle bus speeds of 16.75MHz to 40MHz just fine, in any case. As a result, understanding the operation of the bridge is really only useful for programming broadband adapter drivers.

Tools

• dcload-ip - A program made to transfer .bin and .elf files (and srec files, if specially configured for it) over the BBA. It also provides chainloaded programs with a standard syscall interface for communicating with a networked PC. Mostly intended for homebrew development.
• httpd-ack - Most highly recommended GD-ROM dumping software
• BBRip v1.2 - Now-obsolete Windows-only GD-ROM dumping software for use with dcload-ip (it is recommended to use httpd-ack instead)

Documents

• Realtek RTL8139C datasheet