The Second Shot
The second shot at 1394, the b version, with speeds of up to 800 MBit/s on copper cables and up to 3200 MBit/s using optical fibers, was more than ever overdue - not least because in contrast to its predecessor it also allows cable lengths previously known only to LAN technologies such as Ethernet. But although Lucent announced an IEEE 1394b chipset back in November 1999, it took until 2004 before IEEE 1394b finally became available - with chips from Texas Instruments. The reason was that the U.S. standardization committee IEEE only approved the final 1394b specification at the end of 2003.
Apple launched the first 1394b-capable products onto the market just over half a year ago: Besides its G5 computers and the new successor generations of i- and e-Macs, as well as in the current i-Books and Power Books, the first high-speed FireWire cards for (Windows) PCs are at last available. Trust and Unibrain are already delivering their cards based on the same Texas Instruments chip. Although announced in April 2004, Adaptec's is due in the coming weeks.
FireWire cards are generally delivered without drivers as Windows already provides its own. At Microsoft, IEEE1394 is a component of the Serial Bus Protocol 2 (SPB-2), while the driver is part of the OHCI Protocol Stack (Open Host Controller Interface).
The Microsoft Windows XP operating system currently contains no dedicated drivers for IEEE 1394b. A Microsoft employee provided us with the following statement:
"We have never supported 1394b. It ran under certain conditions on Windows XP and Windows XP SP1. The problem we are confronted with is that OHCI 1.0 and OHCI 1.1 do not support the speed code (0x3). This is a reserved value in the OHCI specification we support that cannot be used."
The Microsoft employee [whose name is known to us] thus confirms the claim of Unibrain that whenever an IEEE 1394b device is connected the throughput sinks to the minimum allowed by the 1394 bus: In the IEEE1394 standard the speed classes such as S100 and S800 are synonymous for signaling rates in MBit/s.
Microsoft maintains its Windows XP Service Pack 2 includes drivers for IEEE 1394b. But according to our tests using the Release Candidate 2 prior to the Service Pack 2's launch earlier this month, a 1394b device's speed dips to a measly 100 MBit/s.
Our source told us: "What are we doing? Things become problematic when you start mixing 1394a and 1394b devices. If we ignore OHCI conformity and bump up the speed to 800 MBit/s the old devices down tools. If we set the speed to S100, all devices start enumerating and working. It was a tough decision but we have little room for maneuver if we don't want to dispense with 1394b support."