IBM System/370 Model 148
| Company type | Computer systems |
|---|---|
| Industry | Computing / Mainframe computers |
| Founded | June 30, 1976 |
| Defunct | November 1, 1983 |
| Products | Mainframe computers |
The IBM System/370 Model 148 and Model 138 were introduced on June 30, 1976. These systems delivered enhanced processing power and better cost-efficiency when compared to the IBM System/370 Model 145 (3145-3 CPU) and Model 135 (3135-3 CPU), respectively, while being offered at considerably reduced prices—$350,000 for a Model 138 equipped with 500K memory versus $721,500 for a Model 135-3 with the same memory capacity.
Positioned as mid-range System/370 computers, the 148 and 138 were designed to upgrade users of the 370/145 and 370/135 models. Both units were discontinued on November 1, 1983.
Expanded capabilities
The Model 148 provided four times the reloadable control storage compared to the 145 (128K instead of 32K), which allowed for advanced features such as:
- APL Assist, a microcode-driven enhancement that sped up APL program execution beyond purely software-based approaches.
- Extended Control Program Support, which improved efficiency by lowering CPU cycle requirements for operating systems—resulting in up to a 20% performance boost for OS/VS1 and as much as a 55% increase for VM/CMS.
Both the 3148 and 3138 models incorporated an integrated service processor (IOC) that could directly connect an IBM 3203 printer and operate an IBM 3277 display console, replacing the older IBM 3215 console, which was typewriter-style and used with the 3145.
Furthermore, IBM launched the Model 4 within the 3203 printer series, offering compact form factor and rapid printing capabilities at a rate of 1200 lines per minute (LPM).
Field upgrades
Known as in-the-field upgrades, this feature was not universally applicable. IBM notably succeeded in upgrading a 370/145 first to a 145-2 and subsequently to a 145-3—a noteworthy accomplishment compared to conventional "forklift upgrades," which require complete system replacements and often lead to significant operational downtime.
Marketing considerations
An industry analyst characterized some units as "early 380s programmed to act like 370s," reflecting IBM’s approach of utilizing existing platform designs while enhancing system functionalities.