PA-RISC Processors

PA-7100LC (PCX-L) processor

Overview

The PA-7100LC is a 32-bit PA-RISC processor from HP introduced in 1994, designed as a single-chip solution for low-cost systems with the performance of comparable workstations and servers. The CPU core is close to the earlier PA-7100 processor and was integrated with FPU, MIOC, first-level cache, onto a single chip with direct GSC main bus attachment.

HP added support for bi-endian byte ordering for the first time to PA-RISC with the PA-7100LC, ostensibly for supporting a wider range of (non-Unix) operating systems. The successor of the PA-7100LC is the similar and improved PA-7300LC processor, released two years later.

Details

PA-RISC version 1.1c, 32-bit architecture, 2-way superscalar
Three functional units: 2 integer ALUs, 1 FPU
Five-stage pipeline
3-instruction queue
Hardware static branch prediction
TLB: 64-entry fully associative; BTLB: 8-entry
Cache L1 1 KB on-chip I L1 instruction cache, prefetch from off-chip cache
Cache L1 up to 2 MB off-chip, direct mapped, 480-600 MB/s bandwidth
Memory and I/O controller MIOC integrated on die, direct memory interface
Support for bi-endian load-store operations
MAX-1 multimedia extensions for multimedia applications, like MPEG decoding
GSC bus interface
Up to to 100 MHz, clock speed
14.2×14.2 mm² die, 900,000 FETs, 0.75µ, 3-layer aluminium process packaged in a 432-pin PGA

Only one of the two integer ALUs is able to handle loads, stores and shifts, these operations can only be paired with simple math operations, like integer addition or multiplication. Both units can handle branch operations.

Used in

HP 9000 712, 715, 725, 743i, 748i VME workstations and V743 VXI workstation
HP 9000 D200, D210, D300, D310 servers
HP 9000 E25, E35, E45, E55 servers
Hitachi 3050RX 225, 235, 255, 535, e9000V V715, V715Tiny, VE25, VE35, VE45, VE55 workstations
SAIC Galaxy 1100 portable workstations

References

PA7100LC ERS (External Reference Specification) (.pdf) Hewlett-Packard Company (1999)
The PA 7100LC Microprocessor: A Case Study of IC Design Decisions in a Competitive Environment Mick Bass et al (April 1995: Hewlett-Packard Journal. Accessed May 2009)
Design methodologies for the PA 7100LC microprocessor (.pdf) Mick Bass et al (April 1995: Hewlett-Packard Journal. Accessed May 2009)

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