NuBus is a 32-bit parallel computer bus developed at MIT and standardized in 1987 as a part of the NuMachine workstation project. The first complete implementation of the NuBus was done by Western Digital for their NuMachine, for the Lisp Machines Inc. LMI Lambda; the NuBus was incorporated in Lisp products by Texas Instruments, used as the main expansion bus by Apple Computer and NeXT. It is no longer used outside the embedded market. Early microcomputer buses like S-100 were just connections to the pins of the microprocessor and to the power rails; this meant that a change in the computer's architecture led to a new bus as well. Looking to avoid such problems in the future, NuBus was designed to be independent of the processor, its general architecture and any details of its I/O handling. Among its many advanced features for the era, NuBus used a 32-bit backplane when 8- or 16-bit busses were common; this was seen as making the bus "future-proof", as it was believed that 32-bit systems would arrive in the near future while 64-bit buses and beyond would remain impractical and excessive.
In addition, NuBus was agnostic about the processor itself. Most buses up to this point conformed to the signalling and data standards of the machine they were plugged into. NuBus made no such assumptions, which meant that any NuBus card could be plugged into any NuBus machine, as long as there was an appropriate device driver. In order to select the proper device driver, NuBus included an ID scheme that allowed the cards to identify themselves to the host computer during startup; this meant that the user didn't have to configure the system, the bane of bus systems up to that point. For instance, with ISA the driver had to be configured not only for the card, but for any memory it required, the interrupts it used, so on. NuBus required no such configuration, making it one of the first examples of plug-and-play architecture. On the downside, while this flexibility made NuBus much simpler for the user and device driver authors, it made things more difficult for the designers of the cards themselves.
Whereas most "simple" bus systems were supported with a handful of input/output chips designed to be used with that CPU in mind, with NuBus every card and computer had to convert everything to a platform-agnostic "NuBus world". This meant adding a NuBus controller chip between the bus and any I/O chips on the card, increasing costs. While this is a trivial exercise today, one that all newer buses require, in the 1980s NuBus was considered complex and expensive; the NuBus became a standard in 1987 as IEEE 1196. This version used a standard 96-pin three-row connector, running the system on a 10 MHz clock for a maximum burst throughput of 40 MB/s and average speeds of 10 to 20 MB/s. A addition, NuBus 90, increased the clock rate to 20 MHz for better throughput, burst increasing to about 70 MB/s, average to about 30 MB/s; the NuBus was first developed commercially in the Western Digital NuMachine, first used in a production product by their licensee, Lisp Machines, Inc. in the LMI-Lambda, a Lisp Machine.
The project and the development group was sold by Western Digital to Texas Instruments in 1984. The technology was incorporated into their TI Explorer a Lisp Machine. In 1986, Texas Instruments used the NuBus in the S1500 multiprocessor UNIX system. Both Texas Instruments and Symbolics developed Lisp Machine NuBus boards based on their Lisp supporting microprocessors; these NuBus boards were co-processor Lisp Machines for the Apple Macintosh line. NuBus was selected by Apple Computer for use in their Macintosh II project, where its plug-n-play nature fit well with the Mac philosophy of ease-of-use, it was used in most of the Macintosh II series that made up the professional-level Mac lineup from the late 1980s. It was used into the mid-1990s. Early Quadras only supported the 20 MHz rate when two cards were talking to each other, since the motherboard controller was not upgraded; this was addressed in the NuBus implementation on the 660AV and 840AV models. This improved NuBus controller was used in the first generation Power Macintosh 6100, 7100 and 8100 models.
Power Mac models adopted Intel's PCI bus. Apple's NuBus implementation used pin and socket connectors on the back of the card rather than edge connectors with Phillips screws inside the case that most cards use, making it much easier to install cards. Apple's computers supplied an always-on +5 V "trickle" power supply for tasks such as watching the phone line while the computer was turned off; this was part of an unapproved NuBus standard. NuBus was selected by NeXT Computer for their line of machines, but used a different physical PCB layout. NuBus appears to have seen little use outside these roles, when Apple switched to PCI in the mid 1990s, NuBus disappeared. Amiga Zorro II Industry Standard Architecture Extended Industry Standard Architecture Micro Channel architecture VESA Local Bus Peripheral Component Interconnect Accelerated Graphics Port PCI Express List of device bandwidths NuBus specs Developing for the Macintosh NuBus Pictures of several NuBus cards at applefritter
The Apple III is a business-oriented personal computer produced and released by Apple Computer in 1980. It was intended as the successor to the Apple II series, but was considered a failure in the market. Development work on the Apple III started in late 1978 under the guidance of Dr. Wendell Sander, it had the internal code name of "Sara", named after Sander's daughter. The machine was first announced and released on May 19, 1980, but due to serious stability issues that required a design overhaul and a recall of existing machines, it was formally reintroduced in the second half of 1981. Development stopped and the Apple III was discontinued on April 24, 1984, its last successor, the III Plus, was dropped from the Apple product line in September 1985; the Apple III could be viewed as an enhanced Apple II – the newest heir to a line of 8-bit machines dating back to 1976. However, the Apple III was not part of the Apple II line, but rather a close cousin; the key features business users wanted in a personal computer were a true typewriter-style upper/lowercase keyboard and an 80-column display.
In addition, the machine had to pass U. S. Federal Communications Commission radio frequency interference qualifications for business equipment. In 1981, International Business Machines unveiled the IBM Personal Computer – a new 16-bit design soon available in a wide range of inexpensive clones; the business market moved towards the PC DOS/MS-DOS platform pulling away from the Apple 8-bit computer line. After numerous stability issues and a recall that included the first 14,000 units from the assembly line, Apple was able to produce a reliable version of the machine. However, damage to the computer's reputation had been done and it failed to do well commercially as a direct result. In the end, an estimated 65,000–75,000 Apple III computers were sold; the Apple III Plus brought this up to 120,000. Apple co-founder Steve Wozniak stated that the primary reason for the Apple III's failure was that the system was designed by Apple's marketing department, unlike Apple's previous engineering-driven projects.
The Apple III's failure led Apple to reevaluate its plan to phase out the Apple II, prompting the eventual continuation of development of the older machine. As a result Apple II models incorporated some hardware, such as the thermal Apple Scribe printer, software technologies of the Apple III. Steve Wozniak and Steve Jobs expected hobbyists to purchase the Apple II, but because of VisiCalc and Disk II, small businesses purchased 90% of the computers; the Apple III was designed to be a successor. While the Apple II contributed to the inspirations of several important business products, such as VisiCalc and Apple Writer, the computer's hardware architecture, operating system, developer environment were limited. Apple management intended to establish market segmentation by designing the Apple III to appeal to the 90% business market, leaving the Apple II to home and education users. Management believed that "once the Apple III was out, the Apple II would stop selling in six months", Wozniak said.
The Apple III is powered by a 1.8 MHz Synertek 6502A or B 8-bit CPU and, like some of the machines in the Apple II family, uses bank switching techniques to address memory beyond the 6502's traditional 64KB limit, up to 256 K in the IIIs case. Third-party vendors produced memory upgrade kits that allow the Apple III to reach up to 512 KB. Other Apple III built-in features include an 80-column, 24-line display with upper and lowercase characters, a numeric keypad, dual-speed cursor control keys, 6-bit audio, a built-in 140 KB 5.25" floppy disk drive. Graphics modes include 560x192 in black and white, 280x192 with 16 colors or shades of gray. Unlike the Apple II, the Disk III controller is part of the logic board; the Apple III is the first Apple product to allow the user to choose both a screen font and a keyboard layout: either QWERTY or Dvorak. These choices cannot be changed while programs were running, unlike the Apple IIc, which has a keyboard switch directly above the keyboard, allowing the user to switch on the fly.
A major limitation of the Apple II and DOS 3.3 is the way it addresses resources, which makes it desirable for peripherals to be installed in standardized locations This forces the user to identify a peripheral by its physical location, such as PR#6, CATALOG, D1, so on. The Apple III introduced an advanced operating system called Apple SOS, pronounced "apple sauce", its ability to address resources by name instead of a physical location allows the Apple III to be more scalable than the Apple II. Apple SOS allows the full capacity of a storage device to be used as a single volume, such as the Apple ProFile hard disk drive. Apple SOS supports a hierarchical file system; some of the features and code base of Apple SOS were migrated into the Apple II's ProDOS and GS/OS operating systems, as well as Lisa 7/7 and Macintosh system software. With a starting price between $4,340 to $7,800 US, the Apple III was more expensive than many of the CP/M-based business computers that were available at the time.
Few software titles besides VisiCalc were available for the computer. Because Apple did not view the Apple III as suitable for hobbyists, it did not provide much of the technical software information that accompanied the Apple II
The Macintosh IIvi is a personal computer designed and sold by Apple Computer, Inc. from September 1992 to February 1993. The IIvi was introduced alongside the Macintosh IIvx, using a slower processor and no floating point unit; the Performa 600 models, are the IIvi with the IIvx's 32 MHz CPU. The IIvi was, on some benchmarks, faster than the IIvx, it is the only model in the Macintosh II family to be branded as a Performa. This was a short-lived Macintosh model, it was discontinued four months after its introduction, when the Centris 650 was introduced at a similar price point. The Performa 600 was featured in the 1994 Disney movie Blank Check. All models include three NuBus slots and a PDS; the Performa 600 models were formally introduced on September 14. Introduced September 14, 1992: Macintosh Performa 600: 4 or 5 MB RAM, 512 KB VRAM, 160 MB HDD, Apple Extended Keyboard II, a microphone. Macintosh Performa 600CD: 5 MB RAM, 1MB VRAM, 160 MB HDD, 2x AppleCD CD-ROM, Apple Extended Keyboard II, a microphone.
Introduced October 19, 1992: Macintosh IIvi: Sold in South America and Japan, but not the United States. Could be configured with 40, 80, 160 or 400 MB HDD. Mac IIvi at lowendmac.com
Apple II series
The Apple II series is a family of home computers, one of the first successful mass-produced microcomputer products, designed by Steve Wozniak, manufactured by Apple Computer, launched in 1977 with the original Apple II. In terms of ease of use and expandability, the Apple II was a major advancement over its predecessor, the Apple I, a limited-production bare circuit board computer for electronics hobbyists. Through 1988, a number of models were introduced, with the most popular, the Apple IIe, remaining changed little into the 1990s. A 16-bit model with much more advanced graphics and sound, the Apple IIGS, was added in 1986. While compatible with earlier Apple II systems, the IIGS was in closer competition with the Atari ST and Amiga; the Apple II was first sold on June 10, 1977. By the end of production in 1993, somewhere between five and six million Apple II series computers had been produced; the Apple II was one of the longest running mass-produced home computer series, with models in production for just under 17 years.
The Apple II became one of several recognizable and successful computers during the 1980s and early 1990s, although this was limited to the USA. It was aggressively marketed through volume discounts and manufacturing arrangements to educational institutions, which made it the first computer in widespread use in American secondary schools, displacing the early leader Commodore PET; the effort to develop educational and business software for the Apple II, including the 1979 release of the popular VisiCalc spreadsheet, made the computer popular with business users and families. The original Apple II operating system was in ROM along with Integer BASIC. Programs were entered saved and loaded on cassette tape; when the Disk II was implemented in 1978 by Steve Wozniak, a Disk Operating System or DOS was commissioned from the company Shepardson Microsystems where its development was done by Paul Laughton. The final and most popular version of this software was Apple DOS 3.3. Some commercial Apple II software did not use standard DOS formats.
This discouraged the modifying of the software on the disks and improved loading speed. Apple DOS was superseded by ProDOS, which supported a hierarchical filesystem and larger storage devices. With an optional third-party Z80-based expansion card, the Apple II could boot into the CP/M operating system and run WordStar, dBase II, other CP/M software. With the release of MousePaint in 1984 and the Apple IIGS in 1986, the platform took on the look of the Macintosh user interface, including a mouse. Despite the introduction of the Motorola 68000-based Macintosh in 1984, the Apple II series still accounted for 85% of the company's hardware sales in the first quarter of fiscal 1985. Apple continued to sell Apple II systems alongside the Macintosh until terminating the IIGS in December 1992 and the IIe in November 1993; the last II-series Apple in production, the IIe card for Macintoshes, was discontinued on October 15, 1993. The total Apple II sales of all of its models during its 16-year production run were about 6 million units, with the peak occurring in 1983 when 1 million were sold.
The Apple II was designed to look more like a home appliance than a piece of electronic equipment. The lid popped off the beige plastic case without the use of tools, allowing access to the computer's internals, including the motherboard with eight expansion slots, an array of random access memory sockets that could hold up to 48 kilobytes worth of memory chips; the Apple II had color and high-resolution graphics modes, sound capabilities and one of two built-in BASIC programming languages. The Apple II was targeted for the masses rather than just engineers. Unlike preceding home microcomputers, it was sold as a finished consumer appliance rather than as a kit. VanLOVEs Apple Handbook and The Apple Educators Guide by Gerald VanDiver and Rolland Love reviewed more than 1,500 software programs that the Apple II series could use; the Apple dealer network used this book to emphasize the growing software developer base in education and personal use. The Apple II series had a keyboard built into the motherboard shell, with the exception of the Apple IIGS which featured an external keyboard.
The Apple II case was durable enough, according to a 1981 Apple ad, to protect an Apple II from a fire started when a cat belonging to one early user knocked over a lamp. Early II-series models were designated "Apple ]["; the first Apple II computers went on sale on June 10, 1977 with a MOS Technology 6502 microprocessor running at 1.023 MHz, 4 KB of RAM, an audio cassette interface for loading programs and storing data, the Integer BASIC programming language built into the ROMs. The video controller displayed 40 columns by 24 lines of monochrome, upper-case-only text on the screen, with NTSC composite video output suitable for display on a TV monitor, or on a regular TV set by way of a separate RF modulator; the original retail price of the computer was US$1298 and US$2638. To reflect the computer's color graphics capability, the Apple logo on the casing was represented using rainbow stripes, which remained a part of Apple's corporate logo until early 1998; the earliest Apple IIs were assembled in Silicon Valley, in Texas.
The Macintosh IIsi is a personal computer designed and sold by Apple Computer, Inc. from October 1990 to March 1993. Introduced as a lower-cost alternative to the other Macintosh II family of desktop models, it was popular for home use, as it offered more expandability and performance than the Macintosh LC, introduced at the same time. Like the LC, it has built-in sound support, as well as support for color displays, with a maximum screen resolution of 640×480 in eight-bit color; the IIsi remained on the market for two and a half years, was discontinued shortly after the introduction of its replacement, the Centris 610. The IIsi's case design is a compact three-box desktop unit used for no other Macintosh model, one of the only Macintosh models of which this is true. Positioned below the Macintosh IIci as Apple's entry-level professional model, the IIsi's price was lowered by the redesign of the motherboard substituting a different memory controller and the deletion of all but one of the expansion card slots and removal of the level 2 cache slot.
It shipped with either a 40-MB or 80-MB internal hard disk, a 1.44-MB floppy disk drive. The MC 68882 FPU was an optional upgrade, mounted on a special plug-in card. Ports included SCSI, two serial ports, an ADB port, a floppy drive port, 3.5mm stereo headphone sound output and microphone sound input sockets. A bridge card was available for the IIsi to convert the Processor Direct slot to a standard internal NuBus card slot, compatible with other machines in the Macintosh II family; the bridge card included a math co-processor to improve floating-point performance. The NuBus card was mounted horizontally above the motherboard. To cut costs, the IIsi's video shared the main system memory, which had the effect of slowing down video especially as the IIsi had 1 MB of slow RAM soldered to the motherboard. David Pogue's book Macworld Macintosh Secrets observed that one could speed up video if one set the disk cache size large enough to force the computer to draw video RAM from faster RAM installed in the SIMM banks.
The IIsi suffers from sound difficulties: over time, the speaker contacts can fail, causing the sound to periodically drop out. This problem was caused by the modular construction of the computer, where the mono loudspeaker is on a daughterboard under the motherboard, with springy contacts. Speaker vibrations led to fretting of the touching surfaces; the problem could be solved by removing the motherboard and using a pencil eraser to clean the contacts of the daughterboard holding the loudspeaker. As the IIsi is the only Macintosh to use this case design, these issues were never corrected in a subsequent model; the IIsi was designed to be and cheaply manufactured, such that no tools were required to put one together – everything is held in place with clips or latches. Because of its heritage as a cut-down IIci, it was a simple modification to substitute a new clock crystal to increase the system's clock rate to 25 MHz for a slight increase in performance. Charles Bukowski was an enthusiastic user of the IIsi.
Macintosh IIsi teardown at ifixit.com
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, an external SCSI peripheral bus, among smaller improvements, it had the same beige-colored case as the original Macintosh, 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. Bruce Webster of BYTE reported a rumor in December 1985: "Supposedly, Apple will be releasing a Big Mac by the time this column sees print: said Mac will come with 1 megabyte of RAM... the new 128K-byte ROM... and a double-sided disk drive, all in the standard Mac box". 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, Zip Drives, 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. The Mac Plus was the first Apple computer to utilize SIMM memory modules instead of single DIP DRAM chips. 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 a new 3 1⁄2-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 incompatible with PC drives; the 800 KB drive has two read/write heads, enabling it to 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; the Mac Plus has 128 KB of ROM on the motherboard, double the amount of ROM that's in previous Macs. For programmers, the fourth Inside Macintosh volume details how to use HFS and the rest of the Mac Plus's new system software; this new filing system allows it to use the first hard drive Apple developed for the 512K, the IWM floppy disk-based Hard Disk 20 and the then-new ROMs allow the Macintosh to use the drive as a startup disk for the first time.
The Plus still did not include provision for an internal hard drive and it would be over nine months before Apple would offer a SCSI drive replacement for the slow Hard Disk 20. It would be well over a year before Apple would offer the first internal hard disk drive in any Macintosh. A compact Mac, the Plus has a 9-inch 512×342 pixel monochrome display with a resolution of 72 PPI, identical to that of previous Macintosh models. Unlike earlier Macs, the Mac Plus's keyboard includes a numeric keypad and directional arrow keys and, as with previous Macs, it has a one-button mouse and no fan, making it quiet in operation; the lack of a cooling fan in the Mac Plus led to frequent problems with overheating and hardware malfunctions. The applications MacPaint and MacWrite were bundled with the Mac Plus. After August 1987, HyperCard and MultiFinder were bundled. Third-party software applications available included MacDraw, Microsoft Word and PowerPoint, as well as Aldus's PageMaker. Microsoft Excel and PowerPoint were developed and released first for the Macintosh, Microsoft Word 1 for Macintosh was the first time a GUI version of that software was introduced on any personal computer platform.
For a time, the exclusive availability of Excel and PageMaker on the Macintosh were noticeable drivers of sales for the platform. The case design is identical to the original Macintosh, it debuted in beige and was labeled Macintosh Plus on the front, but Macintosh Plus 1 MB on the back, to denote the 1 MB RAM configuration with which it shipped. In January 1987 it transitioned to Apple's long-lived platinum-gray color with the rest of the Apple product line, the keyboard's keycaps changed from brown to gray. In January 1988, with reduced RAM prices, Apple began shipping 2- and 4- MB configurations and rebranded it as "Macintosh Plus." Among other design changes, it included the same trademarked inlaid Apple logo and recessed port icons as the Apple IIc and IIGS before it, but it retained the original design. An upgrade kit was offered for the earlier Macintosh 128K and Macintosh 512K/enhanced, which includes a new motherboard, floppy disk drive and rear case; the owner retained the front case, monitor, a
Apple IIc Plus
The Apple IIc Plus is the sixth and final model in the Apple II series of personal computers, produced by Apple Computer. The "Plus" in the name was a reference to the additional features it offered over the original portable Apple IIc, such as greater storage capacity, increased processing speed, a general standardization of the system components. In a notable change of direction, the Apple IIc Plus, for the most part, did not introduce new technology or any further evolutionary contributions to the Apple II series, instead integrating existing peripherals into the original Apple IIc design; the development of the 8-bit machine was criticized by quarters more interested in the more advanced 16-bit Apple IIGS. The Apple IIc Plus was introduced on September 16, 1988, at the AppleFest conference in San Francisco, with less fanfare than the Apple IIc had received four years earlier. Described as little more than a "turbocharged version of the IIc with a high-capacity 3½ disk drive" by one magazine review of the time, some users were disappointed.
Many IIc users had add-ons giving them something rather close to what the new model offered. Before the official release of the machine, it had been rumored to be a slotless version of the Apple IIGS squeezed into the portable case of the Apple IIc. Apple employee John Arkley, one of the engineers working on the Apple IIc Plus project, had devised rudimentary plans for an enhanced Apple IIGS motherboard that would fit in the IIc case, petitioned management for the go-ahead with such a project; when the project started the original plan was to just replace the 5.25-inch floppy drive with a 3.5-inch, without modifying the IIc design. Other features were added as the project progressed, it is believed the Apple IIc Plus design, its existence at all, was influenced by a third-party Apple IIc-compatible known as the Laser 128. It is not a coincidence that the Apple IIc Plus is similar in design to the Laser 128EX/2 model, released shortly before the Apple IIc Plus; as it was backwards-compatible, the Apple IIc Plus replaced the Apple IIc.
Codenames for the machine while under development included: Raisin and Adam Ant. The Apple IIc Plus had comprised three new features compared to the IIc; the first and most noticeable feature was the replacement of the 5.25-inch floppy drive with the new 3.5-inch drive. Besides offering nearly six times the storage capacity, the new drive had a much faster seek time and button-activated motorized ejection. To accommodate the increased data flow of the new drive, specialized chip circuitry called the MIG, an acronym for "Magic Interface Glue", was designed and added to the motherboard along with a dedicated 2 KB static RAM buffer; the second most important feature was a faster 65C02 processor. Running at 4 MHz, it made the computer faster than any other Apple II, including the IIGS. Apple licensed the Zip Chip Apple II accelerator from third-party developer Zip Technologies and added to the IIc Plus; the CPU acceleration was a last-minute feature addition, which in turn made the specialized circuitry for the use of a 3.5-inch drive unnecessary at full CPU speed as the machine was now fast enough to handle the data flow.
By default the machine ran at 4 MHz, but holding down the'ESC' key during a cold or warm boot disabled the acceleration so it could run at a standard 1 MHz operation — necessary for older software that depended on timing games. The third major change was the internalization of the power supply into the Apple IIc Plus's case, utilizing a new miniature design from Sony. Cosmetic changes were apparent as well; the keyboard layout and style now mirrored that of the Apple IIGS and Macintosh, including an enlarged "Return" key and updated modifier keys. Above the keyboard, the used "40/80" switch was replaced by a sliding volume control; the case housing and keyboard had been changed to the light-grey Apple platinum color, creating a seamless blend between keyboard and case, making them appear as one. The machine, a half pound lighter than the original IIc, weighed in at 7 pounds. In the rear of the machine the most obvious change was a three-prong AC plug connector and power switch where the voltage converter had once been, an Apple security port at the far left corner, the standardization of the serial port connectors.
All the same built-in Apple II peripheral equivalents and port functionality of the IIc remained, with the one exception being the floppy port. Whereas the previous IIc could only support one external 5.25-inch floppy drive and "intelligent" storage devices such as the UniDisk 3.5, the Apple IIc Plus offered backwards port compatibility and more. Support for the external Apple 3.5 Drive used by the Apple IIGS and Macintosh was now present, up to two external 5.25-inch floppy drives could be added as well. Internally, the new motherboard sported a pin connector for an internal modem.