The PowerBook G3 is a line of laptop Macintosh computers produced by Apple Computer between 1997 and 2001. It was the first laptop to use the PowerPC G3 (PPC740/750) series of microprocessors. It was succeeded by the Titanium PowerBook G4 line in 2001, which used the PowerPC G4 (PPC74xx) series of microprocessors.
PowerBook G3 (Kanga)
The first Macintosh PowerBook G3, code-named "Kanga," was introduced in November 1997. At the time of its introduction, the PowerBook G3 was advertised as the fastest notebook computer available (a title formerly held by its predecessor, the 240MHz PPC-603ev-based PowerBook 3400c). This model was based on the PowerBook 3400c, and was unofficially known as the PowerBook 3500. It used the same case as the 3400c, and a very similar motherboard. The motherboard was upclocked from 40MHz to 50MHz, resulting in some incompatibility with older 3400 RAM modules. Other changes to the motherboard included doubling the on-board RAM from 16 MB to 32 MB, and a faster version of the on-board Chips and Technologies graphics controller. The G3 made the Kanga more than twice as fast as a 3400c, and the improved graphics controller allowed it to refresh the screen 74 percent faster.
Exec was a company based in San Francisco, USA, that provided companies and individuals access to on-demand personal assistants (for delivery, furniture assembly, research, etc.) and cleaning services. Started by Justin Kan, founder of Justin.tv, in February 2012 with co-founders Daniel Kan, his brother, and Amir Ghazvinian, Exec was backed by Y Combinator and other prominent investors. The company was acquired by Handy (company) in January 2014.
Exec received $3.3 million in seed funding. In September 2013, Exec shut down its errand service to focus on its cleaning service . In January 2014, Handybook, a company founded by Oisin Hanrahan, Umang Dua, Ignacio Leonhardt, and Weina Scott in 2012 announced that it had acquired Exec.
Exec’s errand service had no auction process, and was not an open marketplace. The jobs were dispatched to nearby individuals with the appropriate skills and good ratings, at a flat rate of $38 an hour .
Exec was nominated for Techcrunch's 2012 TechCrunchie Award for Fastest Rising Startup. Exec’s cleaning service garnered positive reviews from web publications such as TechCrunch praising their professionalism and efficiency. Exec also received positive coverage by other publications such as The New York Times, Huffington Post, Forbes, Inc., and Business Insider.
It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritized round-robin scheduling. Exec also provides access to other libraries and high-level inter-process communication via message passing. Other comparable microkernels have had performance problems because of the need to copy messages between address spaces. Since the Amiga has only one address space, Exec message passing is quite efficient. The only fixed memory address in the Amiga software (address 4) is a pointer to exec.library, which can then be used to access other libraries. Exec was designed and implemented by Carl Sassenrath.
Unlike newer modern operating systems, the exec kernel does not run "privileged". Contemporary operating systems for the 68000 such as Atari TOS and SunOS used trap instructions for invoking kernel functions. This made the kernel functions run in the 68000's supervisor mode, while user software ran in the unprivileged user mode. By contrast, exec function calls are made with the library jump table, and the kernel code normally executes in user mode. Whenever supervisor mode is needed, either by the kernel or user programs, the library functions Supervisor() or SuperState() are used.