The Macintosh XL, or: A LISA Mac...
The Macintosh XL is really a modified version of the Apple Lisa computer. The change to this computer was that the computer ships with a Lisa program called MacWorks XL that allows for the emulation of the 64K Macintish ROM, thus enabling the computer to run Macintosh software. The machine is identical to an earlier Lisa 2/10 computer that did not have this software, but only came with the Lisa Operating System.
The Macintosh XL has the standard 400KByte 3.5" floppy drive, the 68000 CPU, 512KByte RAM and an internal 10MByte hard drive. However, unlike the other Macintosh computers, the Macintosh XL uses rectangular pixels for display, due to it's Apple Lisa origin. There was a Macintosh XL Screen kit upgrade available that changed the resulution to more square pixels using a 608x432 resolution instead of the original XL's resolution of 720x364 pixels. RAM could be upgraded to 2MByte using conventional add-in RAM modules.
Motorola 68000 CPU Family
The Motorola 68000 is a 16/32-bit microprocessor that was first released in 1979. It was widely used in computers and other electronic devices during the 1980s and early 1990s. The 68000 was known for its advanced architecture, which included a 32-bit internal bus and a 24-bit address bus, allowing it to access up to 16 megabytes of memory. This made it more powerful than many other processors of its time, such as the Intel 8086 and Zilog Z80. It was also designed to be highly modular and expandable, with a large number of on-chip and off-chip peripherals.
Some of the most famous and successful computers that used the 68000 was the Commodore Amiga and the Atari ST, both of which were popular in the home and personal computer markets. Additionally, it was also used in workstations, such as the Sun 3 and Apollo DN3000, and in a wide variety of embedded systems and industrial control systems. The 68000 was also used in the Macintosh, the first model of the Macintosh was powered by a Motorola 68000 CPU. The processor was eventually succeeded by the 68020 and 68030, which offered improved performance and additional features.
The 68000 has a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The address bus is 24-bit and does not use memory segmentation, making it easier to address memory. There are three ALU's (Arithmetic Logic Unit), two for calculating addresses, and one for data, and the chip has a 16-bit external address bus.
The 68000 architecture was expanded with 32-bit ALUs, and caches. Here is a list with some 680x0 versions and their major improvements:
- 68010 - Virtual memory support
- 68020 - 32-bit ALU & Instruction Cache
- 68030 - On-Chip MMU, 2x 256 byte cache
- 68040 - 2x 4K Cache, 6 stage pipeline, FPU
- 68LC040 - No Floating Point Unit (FPU)
- 68060 - 2x 8K Cache, 10 stage pipelinet