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FireWire 800 under Windows XP SP2
Information on reduced bus speed

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»Update: MS SP2 Patch available

Note

Prior to the release of new hardware, RME carry out extensive tests not onlyof the hardware itself, but also of its compatibility to other hardware. When testing theFireface 800, we found hardware errors of several manufacturers. More information is found inthe Tech Info FireWire 800 Hardware - Compatibility Problems.

FireWire 800 under Windows XP SP2

Windows XP SP1 did not support FireWire800 (1394b). Nevertheless, it worked, although the fullperformance of FireWire 800 wasn't achieved in some cases. With the release of Service Pack 2,Microsoft decided to no longer 'ignore' FireWire 800, but to treat it correctly according to thecurrent OHCI specifications (Open Host Controller Interface). For Microsoft, at this time'correctly' means switching to the slowest transfer mode S100, equalling 100 Mbit per second,for reasons of safety and compatibility.
Microsoft quotes unclear OHCI specifications as the reason for this slow down. Indeed OHCI doesnot clearly define 1394b. Current FireWire 800 chips send a 2-bit speed code of 0x3 (instead of0x2 = S400) in the Self-ID-Packet 0. But OHCI only knows this code as 'reserved'. At a secondglance, however, it becomes obvious that Microsoft have simply not looked closely enough,because there are additional Self-ID-Packets being sent. Self-ID-packet 8 correctly specifiesthe speed with the three-bit code 0x3 = S800. Packet 8 had been already defined in the '1394asupplement', and is therefore not an innovation of FireWire 800.
Microsoft's proceeding is thus at least controversial. In any case, it's a prime example of asomewhat unworldly bureaucratic-mindedness. Since there are no devices that only support S100,the need to throttle the bus speed does not actually exist. At least we do not know of anysuch devices, and as it seems Microsoft did not make this change because of actual complaintsabout incompatibilities. One is simply left wondering...

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Saving the Fireface

This case once again proves the great advantages of a freely configurablehardware. RME has been using FPGAs (Field Programmable Gate Arrays) for years. These can beturned into completely different circuitries by simple flash updates. A combined update offirmware and driver made the Fireface 800 compatible to SP2. For now, the device shows thefollowing behaviour:

• At 1394b interfaces, the Fireface will work with FireWire 800 (800 Mbit/s)
  
• If SP2 is detected, the speed does not decrease to S100, but in one directiononly to S400. In the other direction, S800 stays active. With this, theFireface 800 is still fully operational, just as if it were connected to aFireWire 400 interface (1394a).

This behaviour is introduced with firmware 1.38 and driver version 1.1. The fix will besuccessful for most users, since FireWire 800 is still relatively rare at the moment. If,however, an external FireWire 800 harddisk is to be used successfully alongside the Fireface,FireWire 800 becomes a necessity. This of course can already create a problem, since our fixonly works for the Fireface. An external harddisk would therefore still be operated with S100*under SP2.

*Under SP1, the typical transfer rate of external FireWire 800 harddisks is almostthe same as when using PCI, and when using an internal IDE controller. Our testdrive, a somewhat older IBM, reaches 39 Mbyte/s. With SP2, the value drops to 10Mbyte/s.

Other Manufacturers

Special adaptations from other manufacturers are possible as well. For example, LaCie alreadyprovides a firmwareupdatefor their FireWire 800 harddisks, which brings full performance under SP2. At a closer look,this 'firmware update' seems to install a FireWire filter driver, which knocks out MicrosoftsS800 detection. Since October,Macpower also provides anupdate. Although all external FireWire 800 drives use the same Oxford chip (922), a fix likethis is limited to products of one company. Therefore, owners of no-name PCI cards and no-namedrive cases will probably never get an update or fix...

Back to SP1?

So is it necessary to uninstall SP2 to get back the previously achieved performance? No. It issufficient to install the operating system's old FireWire driver. In fact it is already enoughto exchange two files [1]. Here's how to do it:

• Go to the the hidden WindowsInf directory and copy 1394.inf to anew directory, like 1394_fix.

Before updating to SP2:

• Go to Windowssystem32drivers and copy ohci1394.sys and 1394bus.systo 1394_fix. These files have a date around august 2002, and say SP1 intheir file properties.

If you already updated to SP2: the old ohci1394.sys and 1394bus.sys are found in WindowsDriverCachei386sp1.cab.Copy the files from this archive into the directory 1394_fix.
If you had not installed SP1: the files are found in driver.cab, but this archiveincludes older files that we did not test.

• Install the SP2 update
  
• Go to Windowssystem32drivers and copy these files to 1394_fix:arp1394.sys, enum1394.sys, nic1394.sys

These files are the ones from SP2. There is no need to reinstall all old FireWire drivers. Someof them haven't changed, others are for network use only.
These files are now also found in the sp2.cab, location see above.

• Rename sp2.cab to sp2_dead.cab.

This is necessary, as Windows includes a nice security mechanism, which preventsworst-case-users from accidentally overwriting important driver files with older versions, oreven worse, deleting them completely. So if you try to install the mix of driver files in1394_fix, Windows will automatically install the newer files found in its sp2.cab!

• Make sure the Fireface is switched off and no other external FireWire device ispresent.
  
• Go to Device Manager, FireWire controller (OHCI xxx, 1394 or similar),Properties, Driver, Driver Update. Select 'No, only this time', 'Install from alist or specific location (advanced)', click 'Next', select 'Don't search Iwill choose the driver to install', click 'Next', then 'Have Disk'. Now pointto 1394_fix. Then continue.
  
• Windows will now ask for the path to the file ohci1394.sys and 1394bus.sys.It wants to install the newer ones (see above). Again point to 1394_fix.

That's it. You can now go to Driver Details, and verify that all driver files are from SP2except the ohci1394.sys and 1394bus.sys, which are from SP1. Next reboot, switch on theFireface, and check that the Fireface can perform record/playback.
Finally you can rename sp2_dead.cab back to sp2.cab. Windows will no longer try tocopy the newer driver file until you do a reinstall of the FireWire controller driver. So itmakes sense to activate the driver cache security mechanism again.

[1] In the first version of this Tech Info, only the file ohci1394.sys had been exchanged. Withthis, the throughput rises to good S400. But exchanging the 1394bus.sys as well will activatefull 800 Mbit/s.

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Last update: 10/12/2004

MS Patch available for FireWire 800 and SP2

On December 17, 2004, Microsoft published a Knowledge Base article about the FW800 slowdownproblem under SP2, confirming the behaviour to be a problem of SP2. At the same time MS releaseda file update, which has to be installed manually. The article says this update will not beincluded in later updates and hotfixes, so it must be installed manually whenever needed. Thelink to the article:
http://support.microsoft.com/kb/885222/en-us

Quote: After you install Windows XP Service Pack 2, some 1394 devices (such as digitalcameras that use S400 speed) may not perform as expected. Install this update to helpprevent this issue.

So does it fix the Firewire 800 problems?
Yes, it does. Almost...
The patch installs a new ohci1394.sys, and adds an entry SidSpeed to the OHCI controller in theregistry. The documentation from Microsoft on this patch is disappointing. Here's what we found out:

• After installing this patch, no-name FireWire devices which operate inasynchronous mode seem to be able to use S800, without any further firmwareupdates etc. The IBM disk in the noname drive enclosure that we use (SpeedStar)now reaches 51 MByte/s (38 at S400, 10 at S100). So this patch seems to givefull speed here. Note that the setting SidSpeed had no (in words: none) effecton the transfer rate. It stayed at 51 MB all the time.
  
• After installing this patch, FireWire devices which operate in isochronous modeand support higher speeds are no longer slowed down to S100, but to S400. Thisof course helps the Fireface too, but it still needs our own patch to reachS800 (in one direction). Note that the SidSpeed setting controls the transferrate. Isochronous devices will slow down to S100, S200 or S400 when changingthe reg entry to 0, 1 or 2. According to MS a setting of 3 is expected to givethe old behaviour of SP1 - which is not true. While SP1 enabled S800, SP2 withthis patch enables only S400.

What does this all mean?
RME recommends to install this patch. It will help you to stay compatible, and also delivers nearly thehighest speed possible when using the Fireface. Only users workingwith three Firefaces could gain a bit more performance by using theold SP1, but might run into trouble at other places. Usually thecombination of RME's (driver/firmware included) fix together withSP2 and this MS patch gives trouble-free operation of up to threeFirefaces, and with most other FW devices out there.

Last update: 01/31/2005

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Copyright © Matthias Carstens.
All entries in this Tech Infopaper have been thoroughly checked, howeverno guarantee for correctness can be given. RME cannot be held responsiblefor any misleading or incorrect information provided throughout this manual.Lending or copying any part or the complete document or its contents isonly possible with the written permission from RME.