Home - 2.1 Conservation strategies 2.1.3 From Emulation to Migration

2.1 Conservation strategies

2.1.3 From emulation to migration

Migration is a current strategy applied in the effort to preserve media artworks. Certain technologies at risk due to obsolescence can be replaced by new technologies that are both more efficient and available. However, in some cases, conducting such migrations can by dangerous, as technologies that are too recent may present conservation risks of their own. A lack of knowledge about their maintenance, functioning and installation could lead the restorer and/or conservator to think twice before upgrading this equipment.

 

Migration and emulation strategies share strong similarities in their impact on the integrity and authenticity of an artwork.

 

Migration and emulation are often closely linked to one another. The case of Nu•tka• is a good example of this relationship, with emulation a step in the migration process. The emulation of Nu•tka• will be abandoned in favour of migration once an appropriate technological alternative to the equipment becomes available. The information technology industry offers a fitting illustration of this close proximity between the two strategies. Apple (formerly Apple Computer) uses this emulation strategy often as a transition to technological migration. These successive emulations have allowed users to migrate effortlessly to new technology that is more advanced but less complete from a software point of view. Transitional emulation assures interoperability [1] as well as backward compatibility [2] for the user seeking to upgrade.

 

The table below illustrates the various transitional emulations that Apple has implemented during its hardware and software migrations.[3]


MIGRATION TRANSITIONAL EMULATION COMPLETED MIGRATION
1985

Migration of one line of computers to another. The hardware and software components were different and incompatible.

 

LISA line
------------------------------»
Macintosh line

The Lisa 2 was renamed Macintosh XL, which was delivered with a program that emulated the functioning of the Macintosh and thus made it compatible with programs written for the Macintosh. This emulator (called MacWorks) basically transformed the Lisa 2 into a Macintosh. This is was a software emulation of hardware and software.

The Macintosh XL (last in the LISA line of products) was removed from the Apple catalogue in April 1985.
1984 - 1998

Migration to a new completely different and incompatible processor technology.

 

680x0 to CISC architecture

----------------------------------»

PowerPC to RISC architecture

Transparent software (invisible to the user, as it was integrated into the operating system) that emulated the way the 680x0 CISC processors function on the PowerPC RISC platform.

 

This emulation allowed software written for 680x0 CISC processors to be launched on the new PowerPC RISC line of products. This was a software emulation of old hardware.

In 1998, Apple stopped supporting 680x0. The emulator was no longer included in its operating system.

 

The new operating system (8.5) was faster, as it was optimized for the PowerPC.

 

It was no longer possible to install this new operating system on the 680x0.
2001 - 2007

Migration to a new, completely different and incompatible operating system.

 

Mac OS (Classic) system

-----------------------------------»

UNIX Mac OS X system

The many Mac OS Classic applications were incompatible with Mac OS X.

 

Apple integrated a Mac OS Classic integrator into its new system that allowed the old applications to continue to work. This was a software emulation of a software application.

 

In 2007, a Mac OS X (10.5) update was released that no longer included the Mac OS Classic emulator. All applications were then optimized for Mac OS X.
2006 - 2009

Migration to a new, completely different and incompatible processor technology.

 

PowerPC to RISC architecture

---------------------------------»

x86 line to CISC architecture

An emulator (invisible to the user) was integrated into the system to allow applications written in PowerPC language to function on x86 processors.

 

This emulator, dubbed Rosetta, emulated the PowerPC processors on the x86 platform. This was a software emulation of old hardware.


Apple announced it would no longer support PowerPCs in 2009.

 

With the new update (10.6), it was no longer possible to install Mac OS X on PowerPC processor-based computers. The PowerPC emulator was not included in the 10.6 update. All of the applications were optimized for the x86. The applications became faster, as they were optimized for a specific system that was itself optimized for x86 processors.


 


[1] Interoperability: Capability of two or more functional units to process data cooperatively.

termium.com

[2] Backward compatibility: The ability of existing terminals to receive information from data bases established in future.

termium.com

[3] Apple, available from http://www.apple.com/, accessed 7 July 2009.

Apple-history.com, available from, http://www.apple-history.com/, accessed 7 July 2009.

L'Aventure Apple, available from http://www.aventure-apple.com/, accessed 7 July 2009.