IBM PS/2 Model 70 486
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Founded | June 1988 |
| Headquarters | Boca Raton, Florida , United States |
| Products | Personal computers (desktop and portable) |
The Personal System/2 Model 70 386 and Model 70 486 represent IBM's mid-tier desktop offerings within the IBM PS/2 lineup. Debuting in June 1988, the Model 70 386 is equipped with an Intel 386 CPU operating between 16 and 25 MHz, paired with a 32-bit Micro Channel architecture (MCA) bus. The Model 70 486 followed in December 1989, upgrading to a 25 MHz i486 CPU while retaining the same MCA bus architecture. This latter model essentially incorporates the 486/25 Power Platform CPU upgrade card, initially launched in October 1989 as the first commercial product to utilize the i486 processor. Both systems utilize the chassis design originally introduced with the IBM PS/2 Model 50 in 1987.
Development and release
Both versions were engineered at IBM’s Boca Raton, Florida facility. The initial Model 70 386 became available on June 2, 1988. The project was led by Mark Dean, who previously oversaw development of the IBM PS/2 Model 80, PC AT, and the Industry Standard Architecture bus. Development commenced in 1986 alongside other early PS/2 models. By April 1987, prototypes were demonstrated to select media and insiders, although the official announcement took place in May 1988. Before this release, IBM had introduced the PS/2 Model 80 as its first Intel-based PC featuring a full tower case, originally targeted at multiuser workstation environments but later repositioned for server use, allowing the Model 70 to focus on dedicated workstation roles.
The two models share the same enclosure and tool-free assembly design as the earlier Model 50 from April 1987. Initial production occurred in Boca Raton alongside other PS/2 systems before manufacturing shifted to Raleigh, North Carolina in early 1989 when Florida’s production lines were repurposed. Hard disk drives were manufactured at IBM Japan’s Fujisawa facility.
At launch, the Model 70 series encountered several design difficulties. The Model 70 386-A21 experienced failures due to a defective processor complex slot, prompting a two-month halt in production during early 1989 for motherboard redesigns. In June of that year, IBM issued a recall for specific submodels equipped with faulty 120-MB hard drives suffering from oil lubricant leaks caused by manufacturing flaws at Fujisawa. Although no data corruption was reported, approximately 25,000 units were recalled to rectify drive malfunctions and address error codes detected shortly after purchase.
486/25 Power Platform
In June 1989, IBM unveiled the 486/25 Power Platform upgrade for the Model 70 386-A21, featuring a CPU daughtercard—referred to as a complex—with a 25-MHz Intel 486 microprocessor. This daughtercard replaced the original 25-MHz 386 processor complex, effectively doubling performance compared to typical 33 MHz 386 systems and integrating a built-in floating point unit. Notably, the 486/25 Power Platform was the first commercially available product utilizing the i486 processor, announced just two months following Intel’s launch and shipping by early October 1989.
Shortly after release, a minor calculation flaw was identified in early batches of the i486 processor less than a month later. Although this bug was infrequent and seldom impacted real-world use, IBM suspended shipments of the 486/25 Power Platform until Intel issued a corrected version in December 1989. During this interval, Apricot Computers introduced the VX FT—the world’s first preassembled i486 computer—in early December of that year. Similar to IBM’s Model 70 series, Apricot’s VX FT employed Micro Channel architecture.
On December 19, 1989, IBM launched the PS/2 Model 70 486—the company’s first factory-built system featuring the i486 processor. This model was essentially identical to the Model 70 386 but came with the preinstalled 486/25 Power Platform and refreshed branding. Initial shipments reached enterprise customers in late December 1989, with broader distribution scheduled for mid-January 1990.
Specifications
Every Model 70 variant is equipped with three Micro Channel expansion slots: two 32-bit slots and one 16-bit slot, the latter compatible with select MCA graphics adapters such as the 8514/A.
Model 70 386
The Model 70 386 series debuted in June 1988, initially offering the Model 70 386-E61 (featuring a 16 MHz Intel 386 processor) and the Model 70-121 (with a 20 MHz Intel 386). The E61 came with 1 MB of RAM and a 60-MB ESDI hard disk, while the 70-121 doubled both memory and storage capacity. Both models supported up to 16 MB of RAM and could optionally include an 387 math coprocessor.
In December 1988, IBM unveiled the premium Model 70 386-A21, which featured a redesigned motherboard incorporating a daughtercard with a 25-MHz Intel 386 CPU, a socket for the 387 coprocessor, and a 64 KB SRAM cache managed by an Intel 82385 controller. This configuration included a larger 120-MB ESDI hard drive.
September 1989 saw IBM broaden the lineup with two additions: the Model 70-061, an affordable 20-MHz system equipped with a 60-MB hard drive, and the Model 70-A61, a budget-friendly variant of the A21 that maintained the same processor but offered reduced hard disk capacity.
Following a two-year pause in updates, IBM released four final models in December 1991: the Model 70 386-A81 (25 MHz, 80 MB), A16 (25 MHz, 160 MB), –081 (20 MHz, 80 MB), and –161 (20 MHz, 160 MB). Each of these came standard with 4 MB of RAM. The PS/2 Model 70 386 lineup was phased out in October 1992.
Model 70 486
Launched in December 1989, the Model 70 486 was available in two configurations: the 486-B21 featuring a 120-MB ESDI hard drive and the 486-B61 outfitted with a smaller, 60-MB ESDI drive. Both models utilized a 25 MHz Intel 486 processor and essentially represented rebranded versions of the Model 70-121 and Model 70–061 systems equipped with the preinstalled 486/25 Power Platform. IBM discontinued this series in June 1991, less than two years after its introduction.
Portable model
In May 1989, IBM introduced the PS/2 Model P70, a portable adaptation of the Model 70 386 that weighed , mirroring the desktop’s weight and incorporating a carrying handle for mobility. It was powered by a 20-MHz Intel 386 processor and included 4 MB of RAM alongside an amber-tinted monochrome gas plasma flat-panel display. This release marked IBM’s third effort to penetrate the U.S. portable PC market following earlier unsuccessful attempts with the Portable PC and PC Convertible.
Reception
The PS/2 Model 70 386 received favorable evaluations regarding its performance and cost-effectiveness. Stephen Satchell from InfoWorld described the Model 70 386-121 as "an excellent value," outperforming even the more expensive PS/2 Model 80 equipped with an identical processor. Christopher O'Malley of Personal Computing recognized the Model 70 386-A21 as the fastest among competing machines running at a comparable speed of 25 MHz from manufacturers like Compaq and Advanced Logic Research but pointed out that IBM’s proprietary ESDI interface limited options for upgrading hard drives. Critics praised its capabilities in technical fields such as CAD/CAM but noted it was less ideal for file server applications. Bruce Brown from PC Magazine summarized: "IBM's PS/2 Model 70s blend compact form factors, sophisticated modular engineering, and substantial power across three high-end computers. While expansion possibilities are limited, these systems come well-equipped out of the box."
Submodels
70 486 8570-B21 i486 Intel 486 25 Micro Channel architecture MCA, 32-bit 3 3 single 1.44 MB 120 MB (ESDI) 2 MB 8 MB Video Graphics Array VGA optional Desktop Template:Date table sorting1989,12 70486 8570-B61 i486 Intel486 25 Micro Channel architecture MCA,32-bit 3 3 single1.44MB 60MB(ESDI) 2MB 8MB Video Graphics Array VGA optional Desktop Template:Date table sorting1989,12| Model | IBM P/N | CPU | Operating Frequency (MHz) |
Bus Architecture | 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 | Intel 386 | 25 | 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 1989 09 | |