IBM PS/2 Model 70 386
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Founded | June 2, 1988 |
| Headquarters | Boca Raton, Florida (development) , United States |
| Products | Desktop computer systems (Model 70 386, Model 70 486) |
The Personal System/2 Model 70 386 and Model 70 486 represent mid-tier desktop systems within IBM's Personal System/2 lineup. Introduced in June 1988, the Model 70 386 is equipped with an Intel 386 processor operating at speeds up to 25 MHz, paired with a 32-bit Micro Channel architecture (MCA) bus. The subsequent Model 70 486, which debuted in December 1989, upgraded to a 25 MHz i486 CPU while retaining the same MCA bus architecture. Essentially, this model is a Model 70 386 outfitted with the 486/25 Power Platform CPU upgrade card from the factory, marking it as the first commercial system to incorporate the Intel 486 processor. Both iterations utilize the identical chassis design initially introduced with the IBM PS/2 Model 50 in 1987.
Development and release
Development of both models took place at IBM's Boca Raton, Florida facility. The Model 70 386 was officially launched on June 2, 1988, under the leadership of chief engineer Mark Dean, who previously spearheaded projects such as the IBM PS/2 Model 80, the IBM Personal Computer AT, and the ISA bus. Work on these systems began in 1986 concurrently with other early PS/2 models. Although prototypes were circulating among industry insiders as early as April 1987, IBM formally announced the product line in May 1988. Prior to this, IBM had marketed the PS/2 Model 80 as a tower workstation featuring multiple MCA slots; however, that model was later repositioned towards server applications, leaving the Model 70 to serve as a high-performance workstation option.
Both versions share the same tool-free chassis design found in the earlier Model 50. Initial manufacturing occurred in Boca Raton alongside other PS/2 units before production shifted to Raleigh, North Carolina in early 1989 following IBM’s decision to close its Florida assembly lines to focus on other product ranges. Hard disk drives for these systems were manufactured at IBM Japan’s Fujisawa facility.
At launch, the Model 70 experienced several technical challenges. The Model 70 386-A21 suffered from faulty processor complex slots that led to system instability and failures, resulting in a temporary halt of production and subsequent motherboard redesigns in early 1989. Additionally, in June of that year, IBM issued a recall for approximately 25,000 units equipped with specific hard drives due to leaks of oil lubricant that caused drive malfunctions—this problem was traced back to errors during manufacturing at Fujisawa. Although no data loss was reported, this recall negatively impacted customer trust and required swift remedial measures from IBM.
486/25 Power Platform
In June 1989, IBM introduced the 486/25 Power Platform, an upgrade kit designed for the Model 70 386-A21 which incorporated a CPU daughtercard (referred to as a complex) featuring a 25-MHz Intel 486 microprocessor that replaced the original 386 processor complex. This enhancement effectively doubled processing speed compared to typical 33 MHz 386 configurations and included an integrated floating-point unit inherent to the i486 architecture. Notably, it was the first commercially available system utilizing Intel’s new 486 processor, arriving just two months after Intel’s official launch and shipping began in early October of that year.
Shortly after release, a calculation flaw was identified in initial batches of the i486 processors less than a month later, leading IBM to suspend shipments until December 1989 when Intel addressed and corrected the defect. During this interruption, Apricot Computers launched the VX FT—the world’s first preassembled computer powered by an i486 processor—in early December 1989. Similar to IBM’s Model 70 series, the VX FT also employed Micro Channel architecture.
On December 19, 1989, IBM unveiled the PS/2 Model 70 486 as its inaugural prebuilt system featuring an i486 CPU. This model closely mirrored the earlier Model 70 386 but came standard with the preinstalled 486/25 Power Platform and updated branding elements. Select units were delivered to enterprise customers late in December 1989, with larger-scale distribution scheduled for mid-January of the following year.
Specifications
Every Model 70 variant is equipped with three Micro Channel expansion slots: two 32-bit and one 16-bit slot. The 16-bit slot is compatible with select MCA graphics adapters, including the 8514/A.
Model 70 386
The initial release of the Model 70 386 series occurred in June 1988, offering two configurations: the Model 70 386-E61 featuring a 16 MHz Intel 386 CPU, and the Model 70-121 with a 20 MHz processor. The E61 model came standard with 1 MB of RAM and a 60-MB ESDI hard disk, while the 70-121 doubled both memory and storage capacities. Both models supported RAM upgrades up to 16 MB and included a socket for an optional 387 math coprocessor.
In December 1988, IBM introduced the premium Model 70 386-A21, which featured a redesigned motherboard incorporating a daughtercard with a 25-MHz Intel 386 processor, a socket for the 387 coprocessor, and 64 KB of SRAM cache controlled by an Intel 82385 cache controller. This version was equipped with a larger 120-MB ESDI hard drive.
September 1989 saw the arrival of two cost-effective models: the Model 70-061, a budget-friendly alternative to the 70-121 with a 20-MHz processor and a 60-MB hard drive; and the Model 70-A61, which simplified the A21 by retaining its processor but reducing storage to a 60-MB hard disk.
Following a pause of two years, IBM expanded the Model 70 lineup in December 1991 by introducing four new configurations that offered increased storage options and varied clock speeds: the Model 70 386-A81 (25 MHz, 80 MB), Model 70 386-A16 (25 MHz, 160 MB), Model 70 386–081 (20 MHz, 80 MB), and Model 70 386–161 (20 MHz, 160 MB). Each of these shipped with a base memory of 4 MB RAM.
IBM officially discontinued the PS/2 Model 70 386 series in October of 1992.
Model 70 486
The Model 70 486 was launched in December of 1989, available in two versions: the 486-B21 equipped with a 120-MB ESDI hard drive and the smaller-capacity, 60-MB hard drive-equipped, 486-B61. Both models utilized a 25 MHz Intel 486 processor and were essentially rebranded versions of the earlier Model 70-121 and Model 70-061 but included the preinstalled Power Platform featuring the Intel486/25. IBM ceased production of the Model 70 486 in June of 1991, less than two years after its introduction.
Portable model
In May of 1989, IBM released the PS/2 Model P70, a portable iteration of the PS/2 Model 70 386. Weighing approximately the same as its desktop counterpart and sporting a carrying handle for mobility, it was powered by a single Intel 386 processor running at 20 MHz and came standard with four megabytes of RAM. The display was an amber-tinted monochrome gas plasma flat panel. This launch represented IBM's third attempt to penetrate the U.S. portable PC market following prior unsuccessful efforts.
Reception
The PS/2 Model 70 386 garnered favorable evaluations for its performance and cost-effectiveness. Stephen Satchell from InfoWorld described the Model 70 386-121 as "very good value," emphasizing that it outperformed the more expensive PS/2 Model 80 equipped with an identical processor. Christopher O'Malley from Personal Computing regarded the Model 70 386-A21 as the fastest among available machines running at a clock speed of 25 MHz when compared to competitors from Compaq and Advanced Logic Research, though he noted limited options for upgrading hard drives due to reliance on proprietary ESDI technology. Various reviewers from InfoWorld recommended this system for specialized technical tasks such as CAD/CAM but found it less ideal for use as a file server. Bruce Brown writing for PC Magazine highlighted its compact footprint, modular construction, and processing power while acknowledging restricted expandability; he also pointed out that these high-end models came well-equipped out of the box.
Submodels
| Model | IBM P/N | CPU | Clock Speed (MHz) |
Bus Type | Expansion Slots |
Drive Bays |
FDD | HDD | Base RAM |
Max. RAM |
Graphics Adapter | Display | Chassis Type | Release Date | Remarks |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 70 386 | 8570-061 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 60 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-081 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 60 MB (ESDI) | 4 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-121 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 120 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-161 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 160 MB (ESDI) | 4 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A16 | Intel 386 | 25 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 160 MB (ESDI) | 4 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A21 | Intel 386 | 25 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 120 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A61 | Intel 386 | 25 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 60 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A81 | i386 Intel 386 | 25 | Micro Channel architecture MCA,32-bit | 3 | 3 | single 1.44 MB | 80 MB (ESDI) | 4 MB | 6 MB | Video Graphics Array VGA | optional | Desktop | Template:Date table sorting 1991,06 | |