Sep 97 - Getting Started
Volume Number: 13
Issue Number: 9
Column Tag: Viewpoint
A Cool Rhapsody Web Site & Navigating the
OPENSTEP Doc
by Dave Mark, ©1997, All Rights Reserved
Hopefully, by the time you read this column, you've got a brand-spanking-new
version of Rhapsody humming along on your Power Macintosh. My fingers are crossed!
Either way, be sure to check out John Norstad's excellent Rhapsody web site at
http://charlotte.acns.nwu.edu/jln/wwdc97.html.
The name of the site is the "1997 Apple Worldwide Developers Conference (WWDC)
NUMUG Trip Report, A Rhapsodic Adventure". Don't let the name fool you. This site is
much more than a WWDC rehash. First, it does an excellent job of reviewing the
conference from a technical perspective, but it goes further than that. It presents a
truly understandable picture of Rhapsody from soup to nuts.
The site starts off with a brief introduction, then launches into a discusssion of Apple's
dual OS strategy (Mac OS lives!) and delivery schedules. This is followed by John's
"good news, bad news, good news" perspective on Apple's problems. Next is a detailed
Rhapsody Architecture Overview, complete with architecture diagrams to help you
keep things straight and a discussion of Apple's cross platform strategy.
John graciously allowed me to include some of the material from his site in this
column. Obviously, by the time you read this, the story will have changed somewhat. I
encourage you to visit John's site and get the latest and greatest. And, if you see John at
a conference (he goes to all of them), be sure to thank him for a job well done.
John Norstad on the Blue Box
As you know by now, Apple's new Macintosh architecture includes a Blue Box, which
represents the classic Mac OS rehosted on the Rhapsody core OS, and a Yellow Box,
which represents the new, OPENSTEP based technology, also hosted on the Rhapsody
core OS. Here's some of what John had to say about the Blue Box:
"Blue provides much better compatibility than Copland. For example, almost all
extensions work fine in Blue. Copland would have broken all extensions.
Playing with Blue in the lab was actually quite boring, since it was almost
indistinguishable from a plain Mac running Tempo. That's the whole point, but it was
still boring!
In terms of compatibility for old Mac OS software, the transition from Mac OS to
Rhapsody should be very similar to the very successful transition from 68K to
PowerPC several years ago. Most software will "just work". There will be a few
problems and exceptions, but they should be minor.
The only old software that will break under Blue are programs which talk directly to
hardware without going through the Device Manager, some kinds of extensions which
patch File Manager traps and expect to be able to intercept all file system I/O (Yellow
Box file I/O to shared disk volumes will not be intercepted by these kinds of Blue Box
patches), and any other software that modifies or relies on the internals of shared
system services.
Blue is not an emulator of any kind. It is mostly an exact copy of today's Mac OS,
bug-for-bug, feature-for-feature, just rehosted on the new core OS. Most programs
should run just as fast as they do on Mac OS, or perhaps only a little bit slower. Some
operations will even run faster, due to performance improvements in the core OS.
Blue is very similar to MAE (the "Macintosh Application Environment"), an Apple
product which lets you run Mac software on unix systems. Blue is simpler than MAE
because it does not require a PowerPC emulator. Blue uses a RAM-based ROM image.
There's no hardware ROM.
There is no preemptive multitasking or protected memory inside the Blue Box. A Blue
application that crashes can still take down the entire Blue Box, just like an errant
application on Mac OS can take down the entire Mac. An errant Blue application,
however, cannot crash the core OS or Yellow Box. In Rhapsody, if a Blue crash occurs,
you can easily and quickly reboot just the Blue Box, without having to restart the
entire computer.
To the Mac OS running inside Blue, it appears as if virtual memory is turned off on a
Mac with 1 gigabyte of memory! The core OS does virtual memory operations behind
the scenes, but this is mostly transparent to the Blue Box. There are two important
benefits of this new scheme:
• No more worries about memory fragmentation!
• You can set memory partition sizes very large with no ill-effects for
most applications.