MODE32 is a

software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

product originally developed by

Connectix Connectix Corporation was a software and hardware company that released innovative products that were either made obsolete as Apple Computer incorporated the ideas into system software, or were sold to other companies once they became popular. It ...

for certain models of the

Apple Macintosh Mac is a brand of personal computers designed and marketed by Apple Inc., Apple since 1984. The name is short for Macintosh (its official name until 1999), a reference to the McIntosh (apple), McIntosh apple. The current product lineup inclu ...

. It was published in June 1991 and originally cost

US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...

169; however, on September 5, 1991, the software was made available free to customers under licensing terms with

Apple Computer Apple Inc. is an American multinational corporation and technology company headquartered in Cupertino, California, in Silicon Valley. It is best known for its consumer electronics, software, and services. Founded in 1976 as Apple Computer Co ...

Overview

MODE32 patches the ROM code in certain models of early

68020 The Motorola 68020 is a 32-bit microprocessor from Motorola, released in 1984. A lower-cost version was also made available, known as the 68EC020. In keeping with naming practices common to Motorola designs, the 68020 is usually referred to as t ...

and

68030 The Motorola 68030 ("''sixty-eight-oh-thirty''") is a 32-bit microprocessor in the Motorola 68000 family. It was released in 1987. The 68030 was the successor to the Motorola 68020, and was followed by the Motorola 68040. In keeping with ge ...

computers (see "Affected models" below) which were advertised by Apple to support

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...

memory management. Despite the machines' hardware being designed to support 32-bit mode, the lack of a 32-bit Memory Manager in

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

forced these machines to run in

24-bit Notable 24-bit machines include the CDC 924 – a 24-bit version of the CDC 1604, CDC lower 3000 series, SDS 930 and SDS 940, the ICT 1900 series, the Elliott 4100 series, and the Datacraft minicomputers/ Harris H series. The term SWORD ...

mode, which crippled these otherwise high-end machines to support only 8 MB of

RAM Ram, ram, or RAM most commonly refers to: * A male sheep * Random-access memory, computer memory * Ram Trucks, US, since 2009 ** List of vehicles named Dodge Ram, trucks and vans ** Ram Pickup, produced by Ram Trucks Ram, ram, or RAM may also ref ...

. Prior to licensing MODE32, Apple had been subject to many complaints from individuals over the lack of 32-bit support. Versions of MODE32 prior to 7.5 include a control panel under Macintosh

System 7 System 7 (later named Mac OS 7) is the seventh major release of the classic Mac OS operating system for Macintosh computers, made by Apple Computer. It was launched on May 13, 1991, to succeed System 6 with virtual memory, personal file shari ...

that lets the user enable or disable MODE32. The option to enable 32-bit addressing can be found in the Memory control panel when MODE32 is enabled. Otherwise, the option is not displayed. For System 7.0 and 7.1, MODE32 version 1.2 was recommended. In the case of System 7.5 (and if Thread Manager was loaded), Connectix specifically recommends MODE32 7.5 in order to avoid problems with file corruption. If MODE32 1.2 was installed over 7.5, Connectix recommends a complete reinstall of the operating system. Generally, 32-bit addressing is only needed when large amounts of RAM are needed or when a piece of software requires it. Running non-32-bit-clean software in 32-bit mode on any Macintosh can cause crashes and

data corruption Data corruption refers to errors in computer data that occur during writing, reading, storage, transmission, or processing, which introduce unintended changes to the original data. Computer, transmission, and storage systems use a number of meas ...

. With MODE32 installed, holding down the Esc key on the keyboard as soon as the machine is powered on causes the system to run in 24-bit mode for the current session. Mac OS 7.6 and later require 32-bit "clean" ROMs and do not require this utility. MODE32 is a descendant of Connectix's earlier OPTIMA, which also enables 32-bit addressing but for System 6. Connectix also offered three similar products, MAXIMA, RAM Doubler, and Virtual; the former implemented a

RAM disk A RAM drive (also called a RAM disk) is a block of random-access memory ( primary storage or volatile memory) that a computer's software is treating as if the memory were a disk drive (secondary storage). RAM drives provide high-performance te ...

and latter two adding

virtual memory In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...

(with

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...

in RAM Doubler's case) in addition to allowing addressing 14 MB under 24-bit addressing.Daystar Archive, Mode32 FAQ - LowEndMac
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Affected models

* Macintosh SE/30 *

Macintosh II The Macintosh II is a personal computer designed, manufactured, and sold by Apple Computer from March 1987 to January 1990. Based on the Motorola 68020 32-bit CPU, it is the first Macintosh supporting color graphics. When introduced, a basic ...

* Macintosh IIx *

Macintosh IIcx The Macintosh IIcx is a personal computer designed, manufactured and sold by Apple Inc., Apple Computer, Inc. from March 1989 to March 1991. Introduced six months after the Macintosh IIx, the IIcx resembles the IIx and provides the same perform ...

Other models do not need MODE32 because they either do not support 32-bit addressing at all or support it exclusively.

References

External links

32-bit Addressing on Older Macs
a
Low End Mac

MODE32 7.5 download
at Apple Macintosh-only software