PA-7300LC
| Industry | Computer hardware |
|---|---|
| Founded | January 1, 1939 |
| Products | Microprocessors, computers, printers, software |
The PA-7100LC is a microprocessor that executes the PA-RISC 1.1 instruction set architecture created by Hewlett-Packard (HP). Also referred to as the PCX-L and internally known as Hummingbird, this processor was engineered as an affordable solution for entry-level computing systems. The initial systems utilizing the PA-7100LC debuted in January 1994, operating at clock speeds of 60 and 80 MHz, with a 100 MHz variant introduced in June 1994. It was notable for being the first PA-RISC processor to incorporate MAX-1 multimedia instructions, an early form of SIMD technology designed to improve MPEG video decoding efficiency.
Based on the design of the PA-7100, the PA-7100LC enhanced superscalar performance by incorporating an additional integer execution unit and revising control logic to enable multiple instruction dispatches per cycle, including simultaneous integer and load/store operations. Architectural improvements also encompassed MAX-1 multimedia instructions, support for uncacheable memory regions, and bi-endian capability.
To reduce chip area, the floating-point unit’s multiplier was simplified, preserving a two-cycle latency for single-precision multiplication while extending double-precision multiplies to three cycles—an acceptable trade-off given the processor’s orientation toward mid-range multimedia applications favoring single precision. The processor integrated an on-chip memory controller capable of addressing up to 2 GB of memory alongside an I/O controller, thereby lowering overall system expenses.
Unlike other HP PA-RISC processors that relied on large off-chip instruction and data caches, this model featured a modest 1 KB on-die instruction cache combined with a substantial external unified cache ranging from 8 KB to 2 MB servicing both instructions and data.
The PA-7100LC contains approximately 900,000 transistors within a die measuring 14.2 by 14.2 mm (201.64 mm2). Its fabrication utilized HP’s 0.8 μm CMOS26B process with three metal layers. The processor is packaged in a ceramic pin grid array with 432 pins.
PA-7300LC
Launched in mid-1996, the PA-7300LC served as a low- to mid-tier microprocessor complementing HP’s high-performance PA-8000 in workstation and server platforms. It integrated an enhanced version of the PA-7100LC core along with separate 64 KB instruction and data caches, an L2 cache controller, memory controller, and a GSC bus controller onto a single die. This processor represented the first instance within the PA-RISC family to feature significant on-chip cache memory. The optional L2 unified cache could be configured with parity protection and constructed from register-to-register, flow-through, or asynchronous SRAM technologies.
The PA-7300LC incorporated roughly 9.2 million transistors—of which about 1.2 million were dedicated to logic circuits and approximately 8 million to cache memory—and measured 15.3 by 17.0 mm (260.1 mm2). HP manufactured it using their CMOS14C process, a 0.5 μm CMOS technology operating at 3.3 V with four metal layers.
A distinctive feature of this die is a "silicon doodle" depicting a velociraptor dinosaur located in the upper right corner of the die photograph.
External links
Hummingbird: A Low-Cost Superscaler PA_RISC Processor, lecture by Stephen Undy