Tandem NonStop II

The Tandem NonStop II modernised the original NonStop architecture while preserving its modular, fault-tolerant design and software compatibility. It replaced magnetic-core memory with protected battery-backed dynamic RAM and extended the instruction set to address larger memory spaces.

Customers could expand a running installation by adding processor and I/O modules. Guardian coordinated process pairs, message passing, mirrored storage and recovery so that online transaction applications could survive individual failures.

Notable Features

• Extended addressing increased the usable memory space while retaining the established TNS instruction set.
• Battery-backed DRAM replaced the earlier generation’s core-memory technology.
• Two to sixteen processors could cooperate through duplicated Dynabus connections.

Historical Significance

• NonStop II maintained application compatibility while giving Tandem customers more memory and capacity for growing transaction workloads.
• It became the installed base from which the faster TXP systems and fibre-linked clusters developed.

Collector’s Notes

• NonStop II installations were assembled to order and may contain later storage, communications or processor upgrades.
• Boards and cabinets should be documented together because Tandem systems depended on paired and redundant components.

Specifications

Technical Information
Name	Tandem NonStop II
Manufacturer	Tandem Computers
Launched	Thursday, January 1, 1981
Discontinued	Late 1980s
Country	United States
CPU	Tandem proprietary TNS processor
Units Sold
Power	Redundant, serviceable system power supplies; requirements depended on cabinet configuration
Fault Tolerance	Process pairs, dual buses, battery-backed memory, mirrored storage and online component replacement
Architecture	Extended-address TNS stack architecture in a shared-nothing multiprocessor
Networking	Expand networking; later systems could participate in FOX-linked clusters
Operating System	Guardian / Guardian 90
Expansion / I/O	Dual Dynabus with redundant processor and I/O paths
Keyboard	External operator console terminal keyboard
Storage	Mirrored hard disks, removable disks and magnetic tape through dual controllers
Sound	No general-purpose sound hardware
Graphics	Terminal-oriented text output; no integrated graphics subsystem
Display	External operator console terminal; no integrated display
ROM	Boot, diagnostic and processor microcode storage; capacity varied by generation and configuration
RAM	Battery-backed DRAM; up to approximately 2MB per processor
CPU Speed	100 ns processor cycle; approximately 0.8 MIPS per processor