Vectronic's Macintosh SE
Originally Published: Oct. 7, 2009
Like the Macintosh Plus, the Macintosh SE has a built-in 9-inch monochrome monitor capable of a single resolution of 512 x 342. The monitor displays black and white pixels only. True gray scale is not possible without significant modification through a third-party hack. The video circuits in the Plus and earlier compact Macs spend 50 percent of the RAM access time available during display of a horizontal line, leaving the other 50 percent of that time for doing everything else. The earlier Macs spend all of the time for normal computation during the vertical and horizontal retrace intervals, when the screen is not drawing anything.
The redesigned Macintosh SE motherboard integrates 19 discrete chips found on the Macintosh Plus motherboard into one custom gate array and a PAL. Because this gate can transfer twice as much data at a time into the video circuitry, the Macintosh SE spends only one quarter of the RAM access time servicing the video display. This provides a significant performance boost over the Plus for running applications in RAM. Real world tests show that this arrangement gives the SE a 10 to 20 percent performance boost over the Plus.
The cooling vents found on the top of the older Macintosh Plus have been moved to the front of the machine. The power supply has been beefed up: it has a maximum output of 100 watts and a fan has been added to keep the system cool. The boosted power and fan on the SE allows for the introduction of an internal SCSI hard drive, a feature sorely missing on the fan-less Macintosh Plus.
Internally, the Macintosh SE basically resembles a Macintosh Plus. The SE uses the same 8 MHz 68000 processor. It also has the same SIMM (single in-line memory module) slots as the Plus. The SE has the same sound-generation circuitry as the Macintosh Plus. Many of the discrete components that populated the Macintosh Plus motherboard have been combined into a large gate-array chip on the SE's motherboard.
Apple added a new set of 256K system ROM chips. The amount of code and data in ROM has doubled over the 128K found in the Macintosh Plus. About 160K of this is actual code and resources, comprising the code from the Plus ROM, considerable enhancements to that code, and some of the code libraries that were formerly stored in RAM. The rest of the space is taken up by the Macintosh System fonts. The SE's ROM chips share some of the same code found in the Macintosh II's ROM chips. Some of the identical routines include AppleTalk, TextEdit routines, SCSI Manager, ADB drivers, and the Script Manager.
SE stands for "System Expansion". The Macintosh Plus and all other earlier compact Macs have no means for internal expansion. The Macintosh SE has a single 96-pin slot using a Euro-card type C connector. The slot is mounted on the side of the motherboard. This connector makes un-buffered processor signals and power available to vendor cards that can be plugged into the slot. Due to the cramped interior, the card must be plugged in parallel to the motherboard at the bottom of the Macintosh SE. Cards that require a port use a horizontal access panel located on the back of the computer. One of the first cards Apple made available for the SE was a 5.25-inch floppy disk controller card, with software to translate Macintosh text files to an MS-DOS file format and back again. Apple sold a compatible external 5.25-inch floppy disk drive to use with the card. Other cards available through Apple and third party vendors included coprocessor cards, network cards, 8086-based cards to run IBM-compatible software, monitor cards, and accelerator cards.
The Macintosh SE has the following built-in ports: two ADB (Apple Desktop Bus) ports, one DB-19 floppy drive port, one DB-25 SCSI port, one serial modem port, one serial printer port, and one sound-out jack. The SE does not have a built-in microphone, nor does it have a sound-in jack. The DB-9 mouse port and front plug-in jack for the keyboard found on the Macintosh Plus have been replaced with the Apple Desktop Bus ports on the Macintosh SE. The Apple Desktop Bus decreases the amount of time the 68000 must take to service input devices and makes the design of new input devices much easier. ADB makes it possible to daisy chain up to 16-input devices. Apple would go on to use ADB until the introduction of USB with the iMac in 1998.
The Macintosh SE has two internal drive bays. The Macintosh SE can support up two internal 800K floppy disk drives, one in each bay or one hard drive in the upper bay and one 800K floppy disk drive in the lower bay. The motherboard has two floppy drive connectors and one SCSI connector for use with internal drives. Our Macintosh SE has a special adaptation. It actually has two internal 800K floppy disk drives and one internal 40 MB hard drive that is mounted on top of the upper 800K disk drive. This leaves just enough room to squeeze the hard drive under the CRT circuit board. This configuration is unusual and requires a special drive sled.
Apple initially offered a plethora of configuration options. They even attempted to "brand" the SE with each combination of RAM and drives in each particular configuration. Our Macintosh SE is branded "1 Mbyte RAM, Two 800K Drives". The extra internal hard drive was added later by the former owner. Apple later dropped this confusing branding scheme and simply labeled all configurations "Macintosh SE". Apple initially offered a 20 MB internal SCSI hard drive as an option. Later models could be configured with a 40 MB or 80 MB internal hard drive. The original Macintosh SE did not support 1.4 MB HD disks. Apple later upgraded the motherboard with an FDHD controller and sold this version as the Macintosh SE FDHD.
The Macintosh SE has four RAM slots that support 30-pin SIMMs with a minimum speed of 150 ns. RAM must be installed in groups of two. The minimum RAM offered on the SE was 1 MB and it supports up to 4 MB. RAM sizes can be 256K or 1 MB. The SE does not have any built-in RAM. The system cannot use two-chip 1 MB SIMMs. Our Macintosh SE has 1 MB RAM.
Apple removed the user-accessible compartment for the clock/calendar battery found on the Macintosh Plus. The clock/calendar or PRAM battery on the original SE is powered by a seven-year lithium battery, soldered to the motherboard. Later SEs have a battery mount that uses a standard replaceable 3.6V lithium battery. Our SE's battery still works. We are not sure if it has been replaced sometime in the past, but if it goes out, the only way to replace it is to get out a soldering gun, provided you can find a new battery of this type.
The Macintosh SE originally shipped with System 4.1 (System 4.0 and Finder 5.4) and it supports up to Mac OS 7.5.5. Due to its RAM limitation of only 4 MB, we advise that you don't go any further than Mac OS 7.1. Our Macintosh SE is currently using Mac OS System 6.0.5.
Click to view screen capture 2 - Note the two floppy disks
The Macintosh SE is a highly polished machine that fully addressed the "quirkiness" of previous compact Macs. It is truly modern in many ways. It supports an internal hard drive, has a manageable scheme for adding input devices through the use of ADB, it supports expandability with its internal expansion slot, and it can use a wide variety of SCSI peripherals through its fast SCSI port. Apple replaced the Macintosh SE on August 1, 1989 with the introduction of the Macintosh SE FDHD. The SE FDHD gave the SE the ability to use 1.4 MB floppy disks, but before the SE FDHD hit the market, Apple introduced the Macintosh SE/30 on January 19, 1989. The SE/30 is a significantly upgraded and significantly more expensive variant of the Macintosh SE that uses the Macintosh IIx architecture. Apple sold the SE/30 alongside the SE FDHD until October 1990. The SE line was retired in favor of the low-cost and very popular Macintosh Classic.