486/25 Power Platform
| File:IBM Logo 1986.svg IBM logo used during the late 1980s and early 1990s | |
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Founded | June 2, 1988 |
| Headquarters | Boca Raton, Florida (development) , United States |
Area served | Worldwide |
Key people | Mark Dean (chief engineer) |
| Products | Personal computers (desktop and portable) |
| Parent | IBM |
The Personal System/2 Model 70 386 and Personal System/2 Model 70 486 represent mid-tier desktop computers within IBM's Personal System/2 series. The Model 70 386 debuted in June 1988, equipped with an Intel 386 CPU running between 16 and 25 MHz and utilizing a 32-bit Micro Channel architecture (MCA) bus. Following this, the Model 70 486 was released in December 1989, featuring a 25 MHz i486 processor on the same MCA bus. Essentially, the Model 70 486 is an upgraded version of the Model 70 386 with the 486/25 Power Platform CPU daughtercard integrated—the first commercial system to incorporate the Intel 486 processor. Both models share the chassis design introduced with the earlier IBM PS/2 Model 50 from 1987.
Development and release
The development of both Model 70 variants took place at IBM’s facility in Boca Raton, Florida. The original Model 70 386 was launched on June 2, 1988, led by chief engineer Mark Dean, who had previously overseen projects such as the IBM PS/2 Model 80, the IBM Personal Computer AT, and the ISA bus architecture. Work on these systems began in 1986 concurrently with the initial PS/2 product lineup. Although prototypes had circulated among industry insiders since April 1987, the official announcement did not occur until May 1988. Initially, IBM marketed the PS/2 Model 80 as a workstation suited for multiple users but later repositioned it as a server solution, promoting the Model 70 as their high-performance workstation alternative.
Both models utilize the same chassis and tool-less assembly design found in the earlier Model 50. Production started at Boca Raton alongside other PS/2 units but was transferred to Raleigh, North Carolina in early 1989 after IBM ceased Florida manufacturing to concentrate on other product lines. Hard disk drives were manufactured at IBM Japan’s Fujisawa plant.
At launch, the Model 70 encountered several design challenges. The Model 70 386-A21 experienced failures due to a defective processor complex slot, leading to halted production and motherboard redesigns in early 1989. Additionally, in June of that year, IBM issued a recall for certain submodels equipped with faulty 120-MB hard drives suffering from oil lubricant leaks caused by manufacturing defects at Fujisawa. Although these leaks did not result in data loss, roughly 25,000 units were recalled to address potential reliability issues.
486/25 Power Platform
In June 1989, IBM introduced the 486/25 Power Platform, an upgrade kit for the Model 70 386-A21 that included a CPU daughtercard housing a 25-MHz Intel 486 microprocessor (referred to as a complex). This daughtercard replaced the original processor complex running at 25 MHz and allowed the Model 70 386 to operate at speeds double those of typical 33 MHz 386 systems while also incorporating the i486’s integrated floating-point unit. The 486/25 Power Platform marked the first commercial use of Intel’s 486 processor, announced two months following Intel’s own release and shipped starting in early October 1989.
Shortly after its release, a minor calculation error was discovered in early batches of the i486 processors. Though this flaw seldom impacted practical applications, IBM suspended shipments until December 1989 when Intel provided a corrected version. During this interval, Apricot Computers launched their VX FT system in early December—the world’s first preassembled computer featuring an i486 processor and Micro Channel architecture similar to that of IBM’s Model 70.
On December 19, 1989, IBM unveiled the PS/2 Model 70 486—its inaugural factory-built system equipped with an i486 processor. This model was virtually identical to the earlier Model 70 386 but came with the 486/25 Power Platform already installed and refreshed branding. Initial units were delivered to corporate customers late that month with mass distribution slated for mid-January of the following year.
Specifications
Every Model 70 variant includes three Micro Channel expansion slots: two are 32-bit, and one is 16-bit. The 16-bit slot is compatible with certain MCA graphics adapters such as the 8514/A.
Model 70 386
The Model 70 386 series debuted in June 1988 with two configurations: the Model 70 386-E61 featuring a 16 MHz Intel 386 processor, and the Model 70-121 equipped with a 20 MHz Intel 386. The E61 came standard with 1 MB of RAM and a 60-MB ESDI hard disk, whereas the 70-121 doubled both memory and storage capacity. Both models allowed memory expansion up to 16 MB and included a socket for an i387 math coprocessor.
In December 1988, IBM introduced the premium Model 70 386-A21, which had a redesigned motherboard incorporating a daughtercard with a 25-MHz Intel 386 processor. This design also integrated a socket for the i387 coprocessor and featured 64 KB of SRAM cache managed by an Intel 82385 controller. This edition was equipped with a 120-MB ESDI hard drive.
September 1989 brought two new models: the budget-friendly Model 70-061, running at 20 MHz with a 60-MB drive, and the Model 70-A61, a cost-reduced variant of the A21 that retained the same processor speed but included a smaller 60-MB hard disk.
After a two-year pause, IBM released four final Model 70 386 versions in December 1991: the A81 (25 MHz, 80 MB), A16 (25 MHz, 160 MB), –081 (20 MHz, 80 MB), and –161 (20 MHz, 160 MB), all configured with standard 4 MB RAM. The PS/2 Model 70 386 line was discontinued by IBM in October 1992.
Model 70 486
Launched in December 1989, the Model 70 486 was available in two variants: the 486-B21 with a larger 120-MB ESDI hard drive and the 486-B61 featuring a smaller 60-MB ESDI drive. Both models utilized a 25 MHz Intel 486 processor and were essentially rebranded versions of the Model 70-121 and Model 70-061 respectively, but preinstalled with the 486/25 Power Platform. IBM ceased production of the Model 70 486 in June 1991 after less than two years on the market.
Portable model
In May of 1989, IBM introduced the PS/2 Model P70, a portable adaptation of the PS/2 Model 70 386. Weighing , it featured a carrying handle for mobility. This model was powered by a 20-MHz Intel 386 CPU, came with 4 MB of RAM, and included an amber-tinted monochrome gas plasma display. This represented IBM’s third effort at offering a portable PC in the United States following earlier less successful attempts.
Reception
The PS/2 Model 70 386 earned favorable reviews within business circles. Stephen Satchell from InfoWorld described the Model 70 386-121 as "a very good value," highlighting its superior performance compared to the pricier PS/2 Model 80 equipped with the same processor. Christopher O'Malley of Personal Computing commended the Model 70 386-A21 as the fastest among competitors at its clock speed of 25 MHz, including Compaq, though he noted that upgrading hard drives was limited due to its proprietary ESDI interface. Critics recognized its proficiency in technical fields such as CAD/CAM, while also mentioning subpar performance when deployed as a file server. Bruce Brown from PC Magazine summarized: "IBM's PS/2 Model 70s blend compactness, modular design, and robust performance across three premium-priced machines. Expansion options are limited but they come well-equipped."
Submodels
|70 386 |8570-E61 |i386 Intel 386 16 Micro Channel architecture MCA,32-bit 3 3 one1.44MB 60MB (ESDI) 1MB 6MB Video Graphics Array VGA optional Desktop Template:Date table sorting 1988 06 70 486 8570-B21 i486 Intel 486 25 Micro Channel architecture MCA,32-bit 3 3 one1.44MB 120MB (ESDI) 2MB 8MB Video Graphics Array VGA optional Desktop Template:Date table sorting 1989 12 70 486 8570-B61 [[i486 Intel 486]] 25 Micro Channel architecture MCA,32-bit 3 3 one1.44MB 60MB (ESDI) 2MB 8MB Video Graphics Array VGA optional Desktop {{date table sorting 1989 12}}| Model | IBM P/N | Processor | Clock speed (MHz) |
Bus | No. of slots |
No. of drive bays |
FDD | HDD | Stock RAM |
Maximum RAM |
Video adapter | Monitor | Form factor | Date introduced | Notes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 70 386 | 8570-061 | Intel 386 | 20 | MCA,32-bit | 3 | 3 | one1.44MB | 60MB (ESDI) | 2MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-081 | Intel 386 | 20 | MCA,32-bit | 3 | 3 | one1.44MB | 60MB (ESDI) | 4MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-121 | Intel 386 | 20 | MCA,32-bit | 3 | 3 | one1.44MB | 120MB (ESDI) | 2MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A16 | Intel 386 | 25 | MCA,32-bit | 3 | 3 | one1.44MB | 160MB (ESDI) | 4MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A21 | Intel 386 | 25 | MCA,32-bit | 3 | 3 | one1.44MB | 120MB (ESDI) | 2MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A61 | Intel 386 | 25 | MCA,32-bit | 3 | 3 | one1.44MB | 60MB (ESDI) | 2MB | 6MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-A81 | i386 Intel 386 | 25 | Micro Channel architecture MCA,32-bit | 3 | 3 | one1.44MB | 80MB (ESDI) | 4MB | 6MB | Video Graphics Array VGA | optional | Desktop | Template:Date table sorting 1991 06 | |