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IBM 308X

From Alfawiki
IBM 308X series
IndustryComputer hardware
PredecessorIBM 3033
FoundedNovember 12, 1980; 45 years ago (1980-11-12)
DefunctAugust 4, 1987 (1987-08-04)
ProductsMainframe computers (3081, 3083, 3084)
ParentIBM

The IBM 308X series consists of mainframe computers built on the IBM System/370 architecture, and starting in 1983, incorporated the upgraded System/370 Extended Architecture (S/370-XA). This enhancement extended addressing capabilities from 24-bit to 31-bit, allowing access to significantly larger datasets.[1] This architectural improvement was designed to support IBM's MVS/SP V2 operating system and introduced the Start Interpretive Execution (SIE) instruction, which enabled virtualization through the Virtual Machine/eXtended Architecture Migration Aid.[2]

The first model, known as the Model 3081 Processor Complex, was released on November 12, 1980,[3] and included a processor unit along with its auxiliary components. Later additions to the lineup were the 3083, unveiled on March 31, 1982,[4] and the 3084, announced on September 3, 1982.[5] IBM promoted these machines under the label "System/370-Compatibles."[6] Production of all three models ceased on August 4, 1987.

During the early 1980s, the IBM 308X series was instrumental in enhancing mainframe technology by delivering improved processing power and expanded memory addressing to meet enterprise computing requirements.

IBM 3081

The original IBM 3081 model, designated as the 3081D, provided a processing speed of 5 MIPS. This was succeeded by the faster 7 MIPS 3081K and subsequently by the 5 MIPS 3081G, which debuted on September 3, 1982, replacing the earlier 3081D.[5] The 3081 family offered scalable growth options within the broader 308X range, bridging performance levels between the 3083 and the higher-end 3084 models.[3]

The 3081 incorporated two processors within a single chassis; however, it lacked the capability to partition these processors for independent operation.[7] Both the 3081 and 3083 shared identical physical dimensions, components, and layout—including their CPUs (either 3081 or 3083), service processors with channels (model 3082), and water pump/cooling units (model 3087). The Processor Complex operated on a frequency of 400 Hz power supply, which could be sourced from an optional motor/generator set (model 3089) or an external power input.

Advancement over IBM 3033

Significant technological improvements of the IBM 3081 compared to its predecessor, the IBM 3033, included:

  • Approximately 800,000 integrated circuits realized through large scale integration technology, with individual chips containing up to 704 logic circuits to boost speed and reliability
  • Removal of card-level packaging layers[8]
  • Implementation of water cooling systems for enhanced thermal management beyond traditional air-based cooling
  • A machine cycle duration of just 26 nanoseconds (equivalent to a clock speed of about 38 MHz)
  • Lower power consumption—23 kW for a model 3081-D16 compared to the IBM 3033-U16’s usage of approximately 68 kW
  • Nearly double the rate of instruction execution
  • Two central processing units sharing access to as many as 24 channels and supporting up to 32 MB of main memory[8]

A key packaging breakthrough involved the Thermal Conduction Module (TCM), a flat ceramic substrate containing roughly 30,000 logic circuits distributed over as many as 118 specialized TTL chips. These chips were mounted face-down using a "flip chip" technique onto the TCM's surface with an intricate network of solder pads connecting signals and power across thirty-three metallized layers. Each module interfaced through approximately 1800 pins that handled signal transmission, power delivery, and redundancy.[8]

Heat dissipation was managed by enclosing each chip under a helium-filled metal cap equipped with pistons that pressed firmly against their backsides to efficiently transfer heat. Water-cooled cold plates attached externally maintained chip temperatures near 24 °C, enabling heat fluxes roughly ten times greater than those achieved by the IBM 3033.[8]

Internally, the IBM 3081 project was codenamed Adirondack.[9]

IBM 3083

The IBM 3083 was engineered chiefly to serve the ACP and TPF sectors, focusing on delivering a high-speed uniprocessor solution. Originally, the 308X lineup was intended to comprise only the 3081 and 3084 models; however, the 3083 was introduced later to address this particular market demand.

IBM produced multiple variants of the 3083, each differing in instruction throughput: the CX variant offered the lowest speed, followed by E and EX; B and BX models provided enhanced performance; while J and JX represented the fastest options. Specifically:

  • The CX model operates at roughly 75% of the instruction rate of the EX model.
  • The B and BX variants perform between 1.4 and 1.5 times faster than the E and EX models.
  • The J and JX models execute instructions at approximately 1.8 to 2 times the speed of E and EX.

In total, the highest-performing 3083 model achieves nearly 2.67 times the speed of the slowest version.

IBM 3084

Introduced in September 1982 and discontinued by August 1987, the IBM 3084 supported expanded main memory configurations, scaling from an initial 32 million bytes up to 128 million bytes in later iterations. The premium 3084QX model reached processing capabilities of up to 31 MIPS.

Essentially, the 3084 combined two IBM 3081 units into a symmetric multiprocessing (SMP) system with four processors. It could be configured either as two separate dual-processor systems (PP-mode) or as a unified four-processor system (SI-mode). The physical design doubled the size of previous models by integrating two CPUs along with two cache units (3082) and two floating-point units (3087); when outfitted with optional 3089 processors, two of those were also included.

This architecture provided versatile deployment options suitable for enterprise transaction workloads as well as demanding high-performance computing tasks.

See also

Further reading

  • — Chapter 9 (pp. 241–254) covers detailed architecture information on the 308X series.

Photos

  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named S370-XA
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIE
  3. ↑ 3.0 3.1 Cite error: Invalid <ref> tag; no text was provided for refs named PP3081
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named PP3083
  5. ↑ 5.0 5.1 Cite error: Invalid <ref> tag; no text was provided for refs named PP3084
  6. ↑ IBM Archives
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named GAR.99
  8. ↑ 8.0 8.1 8.2 8.3 Cite error: Invalid <ref> tag; no text was provided for refs named PitPoS
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named CongRec
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