Mac Plus
 |
|
| Also known as | M0001A |
|---|---|
| Release date | January 16, 1986 |
| Introductory price | US$2,599 (equivalent to $5,679 in 2016) |
| Discontinued | October 15, 1990 |
| Operating system | 3.0–6.0.8, 7.0-7.5.5 |
| CPU | Motorola 68000 @ 8 MHz |
| Memory | 1 MB RAM (150 ns 30-pin SIMM), expandable to 4 MB |
| Predecessor |
Macintosh 512K Macintosh XL |
| Successor |
Macintosh SE Macintosh Classic |
The Macintosh Plus computer is the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2599. As an evolutionary improvement over the 512K, it shipped with 1 MB of RAM standard, expandable to 4 MB, and an external SCSI peripheral bus, among smaller improvements. It originally had the same generally beige-colored case as the original Macintosh ("Pantone 453"), but in 1987, the case color was changed to the long-lived, warm gray "Platinum" color. It is the earliest Macintosh model able to run System 7 OS.
Introduced as the Macintosh Plus, it was the first Macintosh model to include a SCSI port, which launched the popularity of external SCSI devices for Macs, including hard disks, tape drives, CD-ROM drives, printers, and even monitors. The SCSI implementation of the Plus was engineered shortly before the initial SCSI spec was finalized and, as such, is not 100% SCSI-compliant. SCSI ports remained standard equipment for all Macs until the introduction of the iMac in 1998, which replaced most of Apple's "legacy ports" with USB.
The Macintosh Plus was the last classic Mac to have a phone cord-like port on the front of the unit for the keyboard, as well as the DE-9 connector for the mouse; models released after the Macintosh Plus would use ADB ports.
The Mac Plus was the first Apple computer to utilize SIMM memory instead of single DIP DRAMs. Four slots were provided and the computer shipped with four 256k SIMMs for 1MB total. By replacing them with 1MB SIMMs, it was possible to have 4MB of RAM. Although 30-pin SIMMs could support up to 16MB total RAM, the motherboard had only 22 address lines connected for 4MB.
It has what was then a new 3.5-inch double-sided 800 KB floppy drive, offering double the capacity of floppy disks for previous Macs, along with backward compatibility. The then-new drive is controlled by the same IWM chip as in previous models, implementing variable speed GCR. The drive was still completely incompatible with PC drives. The 800 KB drive has two read/write heads, enabling it to simultaneously use both sides of the floppy disk and thereby double storage capacity. Like the 400 KB drive before it, a companion Macintosh 800K External Drive was an available option. However, with the increased storage capacity combined with 2-4x the available RAM, the external drive was less of a necessity than it had been with the 128K and 512K.
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Wikipedia