Firewire Enclosures and Support for 120+GB Drives?

smackthud asks: "I'm looking for an external firewire enclosure that works with a new 200GB Western Digital HD w/8mb cache. I tried putting the drive into my ADS pyro enclosure, however, the drive is seen by my G4 iMac as a 128GB drive, which is obviously incorrect. This is not a limitation of MacOSX 10.2 or the iMac, since the HFS+ filesystem supports 2TB+ file systems, and Firewire itself is device size agnostic. The enclosure simply isn't reporting the size of the drive properly. Some research has revealed that most enclosures that use the Oxford 911 bridge chipset do not support ATA100 drives larger than 120GB, while at least one supports up to160GB, but no more. My suspicion is that this is a limitation of the bridge controller's implementation of the ATA100 interface. I've heard that ATA100 had the optional ability to support 48bit address space rather than 32, which would mean that only those vendors who support the optional space would be able to address drives larger than 137GB. This may play a factor in Firewire chipsets which must bridge IDE to IEE1394. Existing products from both WD and Lacie prove that using this drive should be possible, and that any problems with large ATA100 drives have been solved by some vendors. Any helpful information or recommendations would be appreciated."

Comments

ATA/100 tops out at 128GB

[bluestar]

As I understand it, all IDE specs up to ATA/100 are limited to 128GB (or 137(?) if 1GB = 1 billion bytes) by the number of address bits. When the first 160GB IDE drives (from Maxtor) came out they included an ATA/133 controller since all systems at the time only included ATA/100 or lower. ATA/133 increased the number of address bits (I don't know the new limit).

So a FireWire bridge would need to support ATA/133 devices for it to see beyond 128GB on the larger drives.