Rhapsody Developer Release Copyright © 1997 by Apple Computer, Inc. All Rights Reserved.
This release note describes an important problem with file format compatibilities among Rhapsody for PowerPC, Rhapsody for Intel, and OPENSTEP for Mach (pre-Rhapsody) systems.
A fundamental file-system incompatibility exists between Rhapsody and OPENSTEP for Mach/NEXTSTEP (that is, pre-Rhapsody Mach) operating systems. Specifically, Rhapsody for Intel uses a different UFS file-system format than Rhapsody for PowerPC or OPENSTEP for Mach (or NEXTSTEP). There are several consequences to this. You cannot set up systems to dual-boot Rhapsody for Intel and OPENSTEP for Mach (on Intel) operating systems. In addition, you cannot exchange data on external hard disks and removable media between Rhapsody on Intel and earlier OPENSTEP or NEXTSTEP versions of Mach. Since read-write access to older media is not support, attempt this at your own risk.
There are several technical reasons for this situation. Rhapsody is built on the foundation of OPENSTEP for Mach, which uses the big-endian (m68k) UFS file format for all architectural variants (such as OPENSTEP for Mach on Intel). Where it is necessary (such as on Intel systems), OPENSTEP for Mach swaps bytes on file-system structures as it reads them from a disk. For the Developer Release, Rhapsody (in both PowerPC and Intel versions) does not have this byte-swapping code, so the two systems are using incompatible file-system formats. It so happens that Rhapsody on PowerPC uses the same byte sequence as that used by the original big-endian systems; thus Rhapsody on PowerPC can read OPENSTEP for Mach disks created on any architecture. But Rhapsody on Intel cannot read data on externally created UFS disks.
In addition, the native Rhapsody file system is based on the BSD4.4 file system whereas previous Mach versions used the BSD4.3 file-system format. The new file system supports huge (64-bit offset) files and includes other improvements.
In the Developer Release, Rhapsody on PowerPC supports mounting of BSD4.3 disks or partitions in read-only mode.