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Tech Specs

Mac Plus

LEM Staff - 1986.01.16

Introduced in January 1986, two years after the original Macintosh, the Mac Plus shipped with 1 MB of RAM, a new double-sided 800 KB floppy drive, and a built-in SCSI port (the first Mac so equipped). Not only was 1 MB more RAM than PC-class machines could handle, but the Plus could be expanded to 4 MB total RAM! (Earlier Macs came with a fixed amount of memory with no upgrade path.)

Mac Plus with LaserWriter

Macintosh Plus

The SCSI bus on the Mac Plus is officially rated at 1.25 MBps/10 Mbps by Apple, although real world testing shows it to be barely over 0.26 MBps/2.1 Mbps – which is still 4x the speed of Apple’s earlier floppy port hard drive.

The Plus does not support high density floppies, but it can be used with an external high density floppy drive as long as the disks used are 800K floppies.

Macintosh PlusThe original Plus came in Apple beige; during 1987 the case color was changed to platinum, the same color used for almost all post-1986 desktop Macs until the iMac arrived in 1998 (there were a couple black Macs). There are persistent rumors that the power supply in the beige Plus was less reliable and more prone to failure with 4 MB configurations, a problem addressed with an improved power supply in the “platinum” Plus.

The Mac Plus was bundled with MacWrite and MacPaint, and Apple began to bundle HyperCard and MultiFinder in August 1987.

Macintosh PlusUntil the air cooled iMacs came out, all desktop Macs following the Plus and 512Ke up until the slot-loading iMacs have included a fan to reduce internal heat. Because the Mac Plus is convection cooled, you should never block the vents on the side or top of the computer.

Those used to newer Macs will find several keys missing from the keyboard: Esc and Ctrl, along with the Cmd and Option keys to the right of the space bar are simply not there. Neither is the power key, which existed on all Apple ADB keyboards and the first-generation USB keyboard.

The Plus and 512Ke were the last Macs not to use ADB ports for the keyboard and mouse – and the first to use mini DIN-8 serial ports. Discontinued in 1990, the Mac Plus had the longest product life of any Macintosh.

Mac Plus in Star Trek IV

Mac Plus in Star Trek IV

The Mac Plus had a minor role in Star Trek IV: The Voyage Home.

On March 17, 1987, Apple pulled six units and declared them “the one millionth Macintosh”, giving these to Jef Raskin, Steve Wozniak, and others. (Apple Confidential 2.0, p. 98)

The Plus can become a reasonable Web server, as the Macintosh Plus Web Server demonstrated until it was retired in October 2001.

You can convert a non-working compact Mac into a Macquarium. (Please, don’t even think of converting a working one – you can always find someone interested on the Classic Macs or Vintage Macs lists.)

Tips

  • If you have less than 4 MB installed, upgrade to 4 MB. You can often find pulled 1 MB SIMMs (removed from other Macs during upgrade) inexpensively.
  • The Plus cannot use 2-chip 1 MB SIMMs.
  • Memory permitting, set the disk cache to 128k.
  • When a Plus is started-up, it loads the first system it finds in this order: floppy; SCSI ID 6, 5, 4, 3, 2, 1, 0. If you have a drive partitioned, and both partitions have a System Folder, it loads the partition that comes first alphabetically.
  • To use HD floppies, look into the Applied Engineering AE HD+ external floppy drive. They are sometimes available on the used market. Note that the “plus” is important – the AE HD will not do the job.
    You can download drivers for the HD+ drive from the Mac Driver Museum.
  • Rapport, a device called by Kennect Technology, allows you to access 720K DOS disks on a Plus. It attached to the drive port.
  • Because of limited SCSI throughput, older hard drives with no buffer should normally be formatted with a 3:1 interleave for use with the Plus. (Unfortunately, other Macs may find it difficult or impossible to work with this interleave.) This is not an issue for newer drives with data buffers.
  • If you use FWB Hard Disk Toolkit to format your hard drive, be sure to turn off command linking. “The Plus can go a little daft with it on.”

Details

  • introduced 1986.01.16 at $2,600; discontinued 1990.10.15 – at 4 years and 10 months, Apple’s longest lived Macintosh
  • code name: Mr. T
  • Gestalt ID: 4
  • Order no.: M0001A

Mac OS

  • requires System 3.2 (System 3.0 and Finder 5.1) to 7.5.5
  • addressing: 24-bit only

Core System

  • CPU: 8 MHz 68000 CPU
  • ROM: 128 KB
  • RAM: 1 MB, expandable to 4 MB using pairs of 256 KB or 1 MB 150ns 30-pin SIMMs (memory upgrade requires clipping one or two resistors – details online at mia.net; cannot use two-chip 1 MB SIMMs)

Performance

  • Performance: 0.87, Speedometer 3 ; 0.7 MIPS (see benchmarks)

Graphics

  • 9″ b&w screen, 512 x 342 pixels

Drives

  • floppy drive: 800 KB double-sided
  • floppy connector on back of computer
  • Hard drive: external SCSI

Expansion

  • last Mac with keyboard attached via coiled telephone-like cable
  • last Mac with mouse attached via DB-9 connector
  • serial ports: 2 mini DIN-8 RS-422 ports for printer and modem
  • SCSI ports: 1 DB-25 connector on back of computer, slow implementation limited to 2,104 kbps

Physical

  • size (HxWxD): 13.6″ x 9.6″ x 10.9″
  • Weight: 16.5 lb.
  • PRAM battery: 4.5V PX 21 (a.k.a. Eveready 523, ANSI 1306AP, IEC 3LR50)
  • power supply: 60W

Accelerators

  • MicroMac Multispeed (16, 25, or 32 MHz 68030), optional 32 MHz 68882 FPU
  • MicroMac Performer (16 MHz 68030), optional 25 MHz 68882 FPU
  • MicroMac Performer Pro (32 MHz 68030), 64 KB cache, optional 32 MHz 68882 FPU
  • Radius Accelerator 16 (16 MHz 68020 with 68881)

Some accelerators have onboard SIMM slots, allowing them to use more than 4 MB of RAM.

Discontinued accelerators (68030 unless otherwise noted) include the Brainstorm Accelerator Plus (16 MHz 68000), Dove Marathon Racer 030 Plus (16 MHz), MacProducts Railgun (33 MHz), and Novy ImagePro (16, 25, 33 MHz).

Color display? Aura Systems made ScuzzyGraph II, a SCSI peripheral that provided 8-color video for people who didn’t want to buy (or couldn’t afford) a Mac II. 1989 cost was $995 to $2,495, depending on resolution.

Online Resources

Cautions

  • Never connect an Apple II 5.25″ floppy drive to the Mac’s floppy port. Doing so can ruin the floppy controller, meaning you can’t even use the internal drive any longer.
  • That monitor packs a lot of voltage. Read Compact Mac CRT Energy before working inside.
  • The Mac Plus does not provide SCSI termination power, depending on external SCSI devices to provide it. For more details, see SCSI Termination Power.
  • Macs with black-and-white only displays (1-bit, no grays) may find Netscape Navigator 3 makes it impossible to view some pages and sites. The workaround is to use Navigator 2.
  • Reliably supports serial speeds to 19.2 kbps, although default is 9600 bps. May have better throughput at 28.8 kbps despite some dropped and retransmitted packets. Throughput with a 56k modem may be limited. See 56k modem page. For more information on Mac serial ports, read Macintosh Serial Throughput.
  • Zip drives can be used with a Mac Plus, but you have to use Iomega Driver 4.2. Anything newer will not load properly.
  • Apple discontinued support and parts orders for the Plus on 1998.08.31. You may be able to find dealers with parts inventory either locally or on our parts and service list.

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