Low End Mac

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Second Class Macs

Mac LC, a Compromised Mac

Daniel Knight - 2014.03.12

Second Class Macs are Apple’s somewhat compromised hardware designs. For the most part, they’re not really bad – simply designs that didn’t meet their full potential. The Macintosh LC is the oldest Compromised Mac, one of four models sharing the same problems.

Macintosh LCDesigned specifically to be the cheapest color Macintosh to date, Apple cut some corners when designing the LC. It runs a 32-bit 68020 CPU on a 16-bit data bus, making memory access slower than it should have been – all to save the cost of a couple SIMM sockets and keep the motherboard a bit smaller.

Although Apple had moved from the 68020 CPU in the Mac II to the 68030 in the IIx in September 1988, it reintroduced the 68020 with the LC in November 1988. (At the time, the 68020 was considerably less expensive than the 68030.) The . This is because of the LC’s 16-bit data bus.

And where the 68030 can fully support virtual memory, the 68020 doesn’t have that capability built into the CPU.

To add insult to injury, Apple programmed the ASICs to support no more than 10 MB of RAM. With 2 MB on onboard memory and a pair of SIMM slots that support 4 MB modules, this wasn’t seen as much of a limitation at the time. After all, System 6 couldn’t use more than 10 MB, and it was limited to 8 MB on most Macs. With the introduction of the low cost troika (Classic, LC, and IIsi – each one a Second Class Mac), Apple wanted to position the LC specifically for the home and education markets. The company believed that allowing too much RAM might cut into sales of the more expenisve – and profitable – IIsi and IIci.

Of course, had Apple not somehow limited the LC, the IIsi, which supports 65 MB, might have had a very small market.

Apple introduced a new color video standard with the LC – 512 x 384 pixels – along with an inexpensive 12″ color monitor to support it. (In those days, Apple’s 13″ Trintron-based 640 x 480 display sold for about $800!) With a VRAM upgrade, the LC supports 16-bit video on the 12″ monitor and 8-bit video on a standard 640 x 480 screen. Because of the unusual video mode of the 12″ color screen, some programs refused to run with it.

Apple also introduced a low-cost black-and-white 12″ 640 x 480 monitor to complement the LC.

Apple’s one innovation on the LC was the availability of an Apple II emulator for the processor direct slot (PDS), which would help get LCs into schools alongside Apple IIs. This was the primary reason for the 512 x 384 video mode and cheap 12″ color monitor.

The LC was not a horrible Mac, just a compromised one. It was replaced with the 68030-based LC II in March 1992.

Details

  • introduced October 1990 at $2,400; discontinued March 1992
  • requires System 6.0.7 to 7.5.5
  • CPU: 16 MHz 68020
  • FPU: 68881 (optional, uses PDS slot)
  • Performance: 1.8 (relative to SE, compare to 2.4 for Mac II, 2.9 for 20 MHz 68030-based IIsi)
  • RAM: 2 MB on motherboard, expandable to 10 MB using a pair of 100ns 30-pin SIMMs; can use 1 MB, 2 MB, and 4 MB SIMMs
  • video: 256 KB VRAM, expandable to 512 KB; supports 512 x 382 and 640 x 480 resolutions (must have 512 KB VRAM for 8-bits at 640 x 480)
  • L2 cache: none
  • ADB: 2 ports for keyboard and mouse
  • serial: 2 DIN-8 RS-422 ports on back of computer
  • SCSI: DB-25 connector on back of computer
  • LC PDS slot

Keywords: #maclc #macintoshlc #compromisedmac

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