A lot has changed since the first Macintosh. Apple no longer uses a phone connector for its keyboard or DE-9 serial ports for its mouse, printer, and modem. As others have recently pointed out, the only connector still in use from 1984 through today is the analog headphone jack.
Macs have always had some form of serial port, and through much of the Macintosh Era there have been parallel ports as well, most notably SCSI and IDE/ATA, which have been primarily used for hard drives and removable media drives (SyQuest, Zip, CDs, DVDs, etc.). And prior to the 1998 introduction of the first iMac, they all had floppy drives with connectors on the system board.
Peripheral Ports
The original Macintosh and the memory-enhanced 512K have one DE-9 mouse port and two 9-pin RS-422 serial ports on the rear, along with a DB-19 floppy drive port and a headphone jack. There is an RJ11 phone jack on the front for the keyboard.
Keyboard and Mouse Ports
1984-1986, DE-9 Mouse Port
The DE-9 serial mouse port was introduced with the Apple Lisa in 1983, and mice can be freely swapped between Lisas and Macs.
1984-1986, RJ11 Keyboard Port
The early Mac keyboards used the same RJ11 connector as a telephone handset. However, the wiring was reversed, so you couldn’t replace the keyboard cable with a handset cable.
1987-1999, Mini-DIN 4 Apple Desktop Bus
The Apple Desktop Bus (ADB) was introduced with the Apple IIGS in 1986 and came to the Mac in 1987 with the introduction of the Mac SE and Mac II. ADB make provision for turning on the computer using a Power key on the keyboard (right), something Apple also implemented in early USB keyboards. ADB uses the same 4-pin mini-DIN connector (left) as S-video, and most Macs with ADB have two ports.
In theory, ADB can support 16 devices, in the real world up to five, but the Mac OS only supports three. Although ADB can support speeds to 125 Kbps, it generally operates at about 10 Kbps, which is all a mouse, keyboard, or trackball needs. Because of the way the Mac implements ADB, you can have two mice or two keyboards plugged in at the same time.
ADB was used primarily for keyboards, mice, trackballs, and graphics tablets. It was sometimes used as a hardware key for software protection, and there was at least one ADB modem, the 2400 bps Teleport ADB.
ADB was also used in NeXT Computers, the company founded by Steve Jobs after he was ousted from Apple. The last Mac with a built-in ADB port was the 1999 Blue and White Power Mac G3, which was also the first Power Mac with built-in USB ports.
1998-present, USB
With the Rev. A iMac, Apple adopted 12 Mbps USB 1.1 in 1998, retiring Apple Serial Ports (below), SCSI (for the most part), and ADB, except that it appeared on the January 1999 Blue & White Power Mac G3. We’ll cover USB in greater depth after the section on Drive Ports.
Printer and Modem Ports
1984, DE-9 RS-422 Serial Port
Apple’s serial port implementation did not support hardware hand shaking, a decision that would later limit throughput, although it was not a limitation at the time. Apple chose to use the Zilog 8530 chip to manage serial communication; speed was controlled using an external clock signal and could go as high as 1 Mbps. The maximum speed Apple supported was 230.4 kbps, although external hardware could drive it to 1 Mbps.
The serial port was used for AppleTalk networking as well as devices such as modems and printers. AppleTalk networking made it easy to share Apple’s breakthrough and very expensive (nearly $7,000 in 1985) LaserWriter printer among several Macs.
Only the earliest Macs used the DE-9 port. With the 1986 Mac Plus, Apple moved to a DIN-8 port that would remain in use until 1998.
1986-1998, DIN-8 RS-422 Serial Port
Although Apple changed the connector, the electronics remained the same, and the hardware Apple used still supported speeds to 230.4 kbps. Again, it could be externally clocked as high as 1 Mbps. Most Macs had two serial ports.
GeoPort
In July 1993, Apple introduced the Centris 660av and Quadra 840av, the first Macs with built-in digital signal processors (DSP) and an updated serial connector known as GeoPort. Apple used the AT&T 3210 “Hobbit” DSP to manage serial communication, adding a 9th pin to the serial connector to provide additional power for GeoPort devices, such as Apple’s GeoPort Telecom Adapter, which functioned as a modem but could also be integrated to business phone systems.
The new technology supported higher speeds, up to 2 Mbps without the need for an external clock. The GeoPort Telecom Adapter initially supported modem speeds to 9600 bps but over time was updated through software to reach 33.6 kbps. Unfortunately the GeoPort Telecom Adapter tied up a lot of the computer’s resources, much as later WinModems would do in the PC world.
Some Macintosh models had a Communication Slot, which was an internal version of the GeoPort bus. One disadvantage of the Comm Slot is that if a modem was installed in it, the modem port on the back of the computer no longer worked. (The later Comm Slot II found on some PowerPC Macs was a superset of this. On some models, including the Performa 5200, installing a network adapter to the Comm Slot II disabled the printer port.)
GeoPort serial ports made their way into PowerPC Macs and remained in use until Apple adopted USB in 1998.
1998-present, USB
RS-422 serial ports gave way to the much faster USB 1.1 protocol with the release of the iMac in 1998. USB 1.1 supports speeds to 12 Mbps, six times as fast as the GeoPort. We will look more closely at USB in the section on Drive Ports.
Drive Ports
1986-1998, 25-pin external SCSI
When Apple was designing the Mac Plus, it chose to abandon the parallel port use for hard drives on Apple II, ///, and Lisa computers in favor of a newly emerging industry standard, SCSI. SCSI stands for Small Computer System Interface and includes commands, protocols, and electrical standards for connecting devices (mostly hard drives) to “small” computers, which included both personal computers and mini computers, and it was later implemented on “big iron” computers as well.
The original SCSI bus supports up to 8 devices, of which the computer or add-on SCSI card counts as one. There were quite a few revisions of the SCSI standard over time, including some that had a 16-bit interface. Since Apple didn’t use Wide SCSI, we will ignore it here:
- SCSI-1, 1986, 5 MBps, although early Macs came no where near to this level
- Fast SCSI/SCI-2, 1994, 10 MBps
- Ultra SCSI, 2003, 20 MBps
- Ultra2 SCSI, 2003, 40 MBps
- Ultra3 SCSI and beyond are 16-bit protocols
Apple, Amiga, Atari ST, and Sun Microsystems were among the early adopters, and Apple included external SCSI ports on desktop Macs through 1997. Apple also offered an optional SCSI card for the Blue & White Power Mac G3 and its Power Mac G4 line.
1986-Parallel ATA
Apple chose SCSI because it is an intelligent protocol that doesn’t require a great deal of overhead from the CPU. Most of the PC world, were cost was always a factor, had adopted Parallel ATA (also known as IDE and later Ultra ATA). Its origins go back to 1986, the same year SCSI was ratified. It was a much simpler system that originally supported just two devices per bus, known as Master and Slave.
Unlike SCSI, which often supports external devices, Parallel ATA was rarely used for external devices, in part because it has a maximum cable length of 18″ (457mm). Here are the maximum throughput rates and capacities for various implementations:
- IDE, 3.3 MBps, 2.1 GB maximum
- ATA-1, 8.3 MBps, 127 GB maximum
- ATA-2, 16.7 MBps
- ATA-3, added SMART
- ATA-4/Ultra ATA/33, 33.3 MBps
- ATA-5/Ultra ATA/66, 66.7 MBps
- ATA-6/Ultra ATA/100, 100 MBps, 144 PB maximum
- ATA-7/Ultra ATA/133, 133 MBps
- Ultra ATA/166, 166 MBps
In 1994, Apple began using the ATA bus on its consumer models, starting with the 33 MHz 68040-based Quadra/Performa/LC 630 and the 33 MHz 68030-based PowerBook 150. The Quadra 630 used SCSI for its CD-ROM drive and also had an external SCSI port. The PB 150 was the first PowerBook without an ADB port; it also had no SCSI port, so SCSI Disk Mode was not an option.
Going ATA was a cost saving factor that let Apple offer a PowerBook for as little as US$1,450, although PB 150 users will warn you that it has a horrid passive matrix 2-bit grayscale display. And that built-in SCSI? It used an older SCSI controller with a maximum 3 MBps throughput, 60% as fast as the original SCSI standard. That said, the desktop 630 started at US$1,99 and provided a decent level of performance for the time and for its intended market – home and classroom use.
The Power Mac line remained 100% SCSI until November 1997, when Apple introduced the first Power Mac G3 with a 16.7 MBps ATA-2 hard drive bus. At the time, that provided reasonable performance, and the model also included SCSI support, both internal and external, for more demanding users. (Oddly, the internal SCSI bus was 10 MBps, but the external bus topped out at 5 MBps.) It was the last Power Mac with built-in SCSI and the last with a floppy drive.
Parallel ATA began to give way to Serial ATA (SATA) with the introduction of the Power Mac G5 in 2003, something we will cover in the next article.
1998-present, USB
As already mentioned, when Apple introduced the iMac, it replaced ADB, serial ports, and SCSI with one protocol, USB. The iMac used a 16.7 MBps ATA bus for its hard drive and CD-ROM. External connections included 100 Base-T ethernet, a 56 kbps modem, and two USB 1.1 ports.
Compared to ADB and GeoPort, USB was significantly faster with a bandwidth of 12 Mbps (1.5 MBps). That means it was great for keyboards and mice and also good for printers and scanners. But compared to SCSI, well let’s just say that the 1997 Mac SE SCSI bus was faster than USB 1.1. External CD-ROM burners are limited to 4x operation on USB 1.1, and any USB hard drive is horribly hobbled by USB 1.1.
On top of it being rated at 12 Mbps, in the real world no single USB device could use more than about 8 Mbps of bandwidth. (USB 2.0 arrived in 2000, but Apple didn’t adopt it until 2003, so we will cover it in the next article.) There’s a good reason Apple sold a SCSI card for G3 Power Macs once the model with USB shipped. Oh, and that Power Mac G3 had one more thing – FireWire.
1999-2011, FireWire
Apple had developed a new standard to replace aging SCSI with its thick cables and huge connectors. Believe it or not, Apple first conceived of FireWire in 1986, but it wasn’t implemented on a Mac until the Blue & White Power Mac G3 arrived in January 1999, although Apple had offered PCI cards with FireWire since 1997.
It’s fast, as the name implies. The first version used on Macs was 400 Mbps (50 MBps) and came to be known as FireWire 400. Apple added FireWire 800 in January 2003 with the Power Mac G4 (FireWire 800), and over time the FireWire 400 port would disappear from the Mac line. (Yes, 400 and 800 had different connectors.)
Sony used FireWire 400 on some of its digital video cameras, calling it i.LINK and using a different and smaller connector than Apple’s standard FireWire 400 connector.
Living up to its name, FireWire was fast for its day – much, much faster than 12 Mbps USB 1.1 and with higher throughput than 480 Mbps USB 2.0. FireWire even made its way into some PCs, but it was an expensive option that never caught on in the PC market.
2011-present, Thunderbolt
We will look at Thunderbolt in an upcoming article.
Network Ports
1984, DE-9 RS-422 Serial Port
As covered above, the serial port in the earliest Macs topped out at 230.4 kbps, although an external clock could push it to 1 Mbps.
1986-1998, DIN-8 RS-422 Serial Port
The same goes for the DIN-8 serial port used in Macs until the iMac arrived in 1998.
AAUI
There was some question as to which connector was going to becone the norm for ethernet (thick coaxial, thin coaxial, or twisted pair), so Apple hedged its bets by not building a BNC connector or an RJ45 jack into its Quadra, pre-G3 PowerBook, and pre-G3 Power Mac computers, giving them an AAUI port instead. This required the purchase of an expensive AAUI transceiver, and once RJ45 became the norm (circa 1997), Apple dropped AAUI for the much less costly connector.
RJ45 Ethernet Port
The Beige Power Mac G3, introduced in late 1997, was the first Mac with a built-in RJ45 10Base-T ethernet port, which ran at 10 Mbps. Starting with the iMac in 1998, Apple moved to the faster 100Base-T protocol using the same adapter. The Mid 2000 Power Mac G4 was the first Mac with 1000Base-T “gigabit” ethernet.
RJ45 remains the standard ethernet connector, which is a remarkable consistency. The 10Base-T specification was ratified in 1990, and ethernet continues to use the same connector today, although at much higher speeds.
Editor’s note: This was a previously complete article pulled out of our draft archives from 2016.
