Monday, September 06, 2004

Intech SpeedTools Utilites for MacOS X - Problems with Firewire!

Intech Software Online:Product Info:SpeedTools Utilites

After my firewire debacle (see prior posts) I have a renewed interest in this sort of product. This does a lot of different things, including allowing one to create huge FAT32 drives from OS X.

It's not cheap at $90, but it may be bundled with some drives.

It includes the very interesting SpeedTools Device Tuner (for Oxford chipset bridged firewire enclosures)
DeviceTuner was initially created to solve the problems of a particular FireWire device’s ability to transfer data reliably over a FireWire bus. Being unable to copy files to or from a FireWire hard disk, for example, is a common symptom of a larger problem: less than optimal signal quality on the FireWire bus. This can be caused by a myriad of factors, but regardless of why it happens, DeviceTuner can likely help.

FireWire troubleshooting education can quickly become quite complex. Therefore, if you have interest in the "nuts and bolts" of how this product works, Intech strongly recommends that you download the Device Tuner User's guide from the link near the bottom of this page.


Controls FireWire payload sizes on an individual or global basis
FireWire "Safe Mode" for maximum compatibility

Data is exchanged between FireWire devices in discrete packets of various size. Currently, these packet sizes (called payload) can vary from as little as 4 bytes to as much as 4096 bytes. Most FireWire devices default to anywhere between 1024 to 4096 bytes per packet to achieve maximum speed. This works well for most devices connected to Macintosh computers. However, as more devices get added to a FireWire bus, signal quality can degrade below the threshold that will allow larger data packets to transfer reliably. Furthermore, older Macs (like first generation PCI Power Macs) using older PCI FireWIre host adapters seem to also frequently have marginal signal quality which result in data transfer errors with larger packets.

In situations like these, DeviceTuner can make the difference between data transfer errors and perfect data transfer. Device Tuner allows you to restrict the maximum size of a data packet that a given supported device will use. It works by overriding the payload sizes negotiated between the MacOS and the device. Unfortunately, this tactic does not work with all devices, especially early FireWire disk drives. Note: Be aware that there is always a tradeoff: the lower the packet size, the slower the maximum speed, and visa versa. In a very real sense, Device Tuner does NOT solve the bus's underlying signal quality degradation problem. It just allows you to reduce a device’s FireWire bus payload by reducing packet sizes below the levels which manifest data transfer problems.

This reminds me all too much of my ancient PowerBook 165 SCSI bus experiences. Sigh. One needs the very best cables -- all from one vendor. The very best devices. The very best patience ...

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