PA-RISC information - since 1999

PA-RISC Performance and CPU History

Overview

HP developed three generations of PA-RISC processors between the 1980s and 2000s. Processors of the Precision Architecture, also called HP-PA, were used in many HP Unix technical computers, competing with other contemporary RISC architectures.

  1. PA-RISC 1.0 32-bit, implemented in early 1980s processors and used in first PA-RISC servers: NS-1, NS-2 and PCX, plus the TTL TS-1 and maybe others.
  2. PA-RISC 1.1 32-bit, used in popular HP 9000 servers and workstations from the late-1980s to 90s: PA‑7000 and PA‑7100 and integrated PA‑7100LC and PA‑7300LC.
  3. PA-RISC 2.0 64-bit, used in many 1990s/2000s HP computers: PA‑8000/PA‑8200 and the updated PA‑8500, PA‑8600 and PA‑8700 with large on-chip caches. PA‑8800 and PA‑8900 are dual-core, with the final PA‑9000 never implemented.
HP PA
© HP 1986

HP Precision Architecture is an offspring from HP research and development in the 1980s to replace 16-bit stack-based CPUs in HP 3000 servers and Motorola CPUs in Unix systems with a common system architecture. PA-RISC platform and ISA were built from the ground up by HP engineers.

PA-RISC was implemented almost exlusively in HP processors in its VLSI Technology Center (VTC) and Systems & VLSI Technology Operation (SVTO), from early version in TTL and NMOS in the 1980s to integrated 32-bit and 64-bit RISC processors in the early 2000s with modern technologies.

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PA-RISC 32-bit in the 1990s

PA-7000

HP PA-7000 PA-RISC processors (1991) were average RISC performers of the early 1990s with roughly the same performance as MIPS R3000A (1992), Motorola 88100 (1988) and SPARC (1991 implementations) but slightly slower than IBM POWER1 (1990), Sun SuperSPARC (1992) and MIPS R4000 (1991) at similar clocks.

Compared to personal computers in that era, PA-7000 were faster than Intel 486DX2 (1992) and level with later Pentium P5 (1993) at the same frequencies, but significantly stronger in floating point than both.

PA-7100

HP PA-7100 PA-RISC processors were rather fast microprocessors for their time in 1992, on par with their RISC competition and beating even newer processors in floating point. At the same clock, PA-7100 were almost level with Pentium P54C (1994) and MIPS R4400SC (1992) but significantly faster in floating point, SPEC95.

They were significantly faster than DEC Alpha 21064 (1992), slightly faster than IBM PowerPC 604 (1994) but beaten by higher-clocked Intel Pentium Pro (1995).

PA-7100LC

HP PA-7100LC PA-RISC were fast, integrated low-cost microprocessors in 1994, on par with RISC and PC architectures of the time. At the same clock, PA-7100LC were in the ballpark of IBM PowerPC 604 (1994) and beat Pentium P54C (1994) and MIPS R4400SC (1992) in SPEC92 scores. They were much stronger in floating point.

As MPR put it, PA-7100LC were significantly faster than the PowerPC 601 and dramatically faster than the TI microSPARC, and had far better FP performance than Sun’s microSPARC II and outran the fastest SuperSPARC chip in SPEC92 scores.

PA-7200

HP PA-7200 PA-RISC were very strong microprocessors for 1995, usually above their RISC competition in technical computing. PA-7200 were much faster than IBM PowerPC 604 (1994), Pentium P54C (1994) and MIPS R5000 (1996) at similar frequencies with almost twice the performance in floating point.

PA-7200 were almost equal to higher-clocker Pentium Pro (1995) and UltraSPARC (1995) and not far from Digital Alpha 21164 (1996) at significantly higher clock.

PA-7300LC

HP PA-7300LC PA-RISC were solid low-cost RISC processors, on par with competing microarchitectures in 1996. At the same clock, PA-7300LC were slightly faster than Sun UltraSPARC (1995), Pentium Pro (1995) and PowerPC 604e (1996), in SPEC95 scores. Floating point results were weaker.

In comparison, MIPS R10000 (1996) and Pentium II (1997) processors beat PA-7300LC only at higher clock rates. The 64-bit PA-8000 follow-on PA-RISC processors from HP were about 30% faster, at the same clock.

PA-RISC 64-bit (90s/2000s)

PA-8000

PA-8000 performance
PA-8000 performance, © HP 1996

HP PA-8000 PA-RISC were very fast 64-bit microprocessors in 1996, above their RISC competition for technical computing. PA-8000 were faster than IBM PowerPC 604e (1996), Pentium Pro (1995), Pentium II (1997) and MIPS R10000 (1996) at similar to higher clockspeeds, and much stronger (almost twice) in floating point.

PA-8000 were almost par with Pentium II (1997) and UltraSPARC IIi (1997) that were sold at significantly (twice) higher clocks. They were more than ⅓ faster at the same clock than their 32-bit PA-7200 and PA-7300LC predecessors.

PA-8200

PA-8200 Performance
RISC Performance in ’97 © MPR Conference

HP PA-8200 PA-RISC were again very fast 64-bit microprocessors in 1997, and above much of the RISC competition in technical computing. They were significantly faster than Pentium II (1997), UltraSPARC IIi (1997) and Digital Alpha 21164A (1996) that had twice the clockspeed.

Newer MIPS R10000 CPUs (1996/1997) with large caches were only slightly slower than PA-8200. PA-8200 in turn were a bit faster than the core 64-bit PA-8000, released a year earlier (1996) at lower frequencies.

PA-8500

HP PA-8500
© MPR 1999

HP PA-8500 PA-RISC were some of the fastest 64-bit microprocessors in 1998. They were significantly faster than Pentium II (1997), Pentium III (1999) and Digital Alpha 21264 (1998) at the same or higher clock speed. IBM POWER3 (1998) and UltraSPARC IIi (1997) were almost on par at the same clock. SGI MIPS R12000 (1998) was slower than PA-8500 and only sold at lower frequencies.

PA-8500 was shipped with higher clock speeds than earlier 64-bit PA-8200 (1997) and a bit faster in integer and significantly faster in floating point. Notably, it won the Microprocessor Report’s Best RISC Processor in 1999, when it is destined for the scrap heap. (i.e. decommissioned for Itanium)

PA-8600

HP PA-8600 PA-RISC were fast 64-bit microprocessors of the early millenium (2000) and followed the PA-8500 performance-wise with slightly higher frequencies. The PA-8600 were in the same ballpark as higher clocked UltraSPARC III (2001), Pentium III Xeon (1999) and faster than (slightly outdated) Digital Alpha 21264 (1998).

Performance was even with IBM RS64-VI (2000) and MIPS R14000 (2001) RISC processors at similar clock, while the newer Digital Alpha 21364 (2001) was faster at higher frequencies.

PA-8600 was notably faster than the first Itanium Merced (2001) from HP and Intel at higher clockrates, which in turn were much stronger in floating point (50%).

PA-8700

HP PA-8700 PA-RISC (2001) were still fast 64-bit CPUs in the early 2000s when competitors started increasing clock speeds for more performance. PA-8700 were in the same ballpark as higher clocked UltraSPARC III (2001), Alpha 21364 (2001) and IBM POWER4+ (2003), faster than Pentium III Xeon (1999) and almost even with MIPS R14000 (2001).

The first Itanium Merced (2001) from HP and Intel was notably much slower than PA-8700 in integer but on par in floating point, while the second generation Itanium McKinley (2002) was faster with more than double the floating point performance.

PA-8800

When it became clear in the late-1990s Itanium Merced processors will be significantly delayed until the early 2000s, HP decided to extend the life of PA-RISC for a few more years. HP’s plan by 1998 was to integrate two PA-8x00 64-bit cores onto a single processor with large caches: enter the PA-8800 and PA-8900 CPUs.

With this development, HP could offer performant PA-RISC processors in parallel to Itanium for four years to ease transition to the new IA64 architecture.

HP PA-8800 PA-RISC were last of the line of 64-bit PA-RISC processors, released in 2004. The dual-core integration was the last development step to increase the performance of the original PA-8000 core. Few formal SPEC benchmark scores exist and PA-8800 was offered in only some niche PA-RISC systems in the mid-2000s.

PA-8800 was a very fast RISC processor when released in 2004 and much faster at the same clockspeed than Alpha 21364 (2001), IBM POWER4+ (2003), Itanium McKinley (2002). It was in the same ballpark as AMD Athlon XP (2002), Intel Xeon DP (2003) and Pentium 4 Prescott (2003) at much higher (more than double) the frequencies.

PA-8900

HP PA-8900 PA-RISC were the pinnacle of 64-bit PA-RISC processor design (2005), but improved on the PA-8800 only slightly. No formal SPEC benchmark scores exist and PA-8900 were sold only really as a slightly enhanced upgrade to PA-8800-based 64-bit PA-RISC systems. This way, PA-RISC stayed competitive for a few more years.

Based on PA-8800 performance, PA-8900 was still pretty quick in 2005, faster at the same clockspeed than Alpha 21364 (2001), IBM POWER4+ (2003) and Itanium McKinley (2002). Contemporaries such as AMD Athlon XP (2002) and Intel Xeon (2003) had similar performance at much higher frequencies, AMD Opteron (2005) was faster.

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Performance

The main competitors of PA-RISC were other Unix platform vendors with their own RISC architectures: Sun SPARC (Solaris), Digital Alpha (Tru64 and OSF), SGI with MIPS (Irix), and IBM POWER (AIX and others). In the late 1990s, Intel Pentium and P6-based sucessors also became serious competitors (Windows and Linux).

While PA-RISC processors were usually faster than their competition at the same clock speed, they were expensive to fabricate. Their platform, HP 9000 with PA-RISC and HP-UX, was usually exclusively priced in the 1980s and 1990s, compared to other Unix vendor ecosystems.

Companies such as HP and IBM can justify developing very-high-end processor designs, even though the unit volume will be small, because the profits per system are far higher than the profits per microprocessor chip, as MPR put it in 1992.

PA-RISC was often used for specialized technical workloads that made use of their strengths in floating point and numerical processing, as part of an integrated HP 9000 and Unix ecosystem.

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SPEC comparisons

Relative performance between computers and architectures can be compared by benchmark scores like the SPEC suite, often for scoring CPU and instruction performance. For the Unix and RISC systems covered here, SPEC95 and SPEC2000 had the greatest match, using the CPU integer (CINT) and floating point (CFP) results.

PA-RISC traditionally was a fast architecture compared to other RISCs. When others like Alpha and Intel P6 derivates increased frequencies in the late 90s, PA-RISC stayed with comparatively lower clock speeds. The following results are synthetic benchmarks dependant on compilers and operating systems, scores were notably higher in HP-UX 11.00 than in 10.20, for example.

Typical SPEC scores on HP PA-RISC computers
Processor Clock Year SPEC95
int  fp		 SPEC2000
int  fp
PA-7000 50 MHz 1991 1.20 2.00
PA-7100 75 MHz 1992 1.53 2.46
PA-7150 125 MHz 1992 3.97 4.61
PA-7100LC 100 MHz 1994 3.76 4.06
PA-7200 120 MHz 1995 6.06 8.14
PA-7300LC 180 MHz 1996 9.22 9.43 87 60
PA-8000 180 MHz 1996 11.80 18.70
PA-8200 200 MHz 1997 14.20 21.40
PA-8500 440 MHz 1998 31.80 52.40 313 321
PA-8600 552 MHz 2000 42.10 64.00 432 433
PA-8700 750 MHz 2001 57.60 85.90 604 576
PA-8800 1 GHz 2004 1001 est.
PA-8900 1.1 GHz 2005
Comparison SPEC scores of other architectures
Processor Clock Year SPEC95
int  fp		 SPEC2000
int  fp
Sun SuperSPARC 40 MHz 1992 1.13 1.38
DEC Alpha 21064 100 MHz 1992 1.48 2.79
Sun SuperSPARC II 75 MHz 1994 3.11 3.10
IBM PowerPC 604 100 MHz 1992 3.59 3.20
MIPS R5000 150 MHz 1996 3.97 4.20
DEC Alpha 21064A 266 MHz 1993 4.18 6.27
Intel Pentium 100 MHz 1994 4.04 2.35
Intel Pentium Pro 166 MHz 1995 7.11 6.21
DEC Alpha 21164 300 MHz 1998 7.33 12.20 161 158
IBM PowerPC 604e 166 MHz 1996 7.52 8.52
MIPS R10000 196 MHz 1996 10.1 8.7
Intel Pentium II 333 MHz 1997 13.0 9.4
Sun UltraSPARC IIi 333 MHz 1997 14.1 18.3 133 126
Intel Pentium III 500 MHz 1999 20.7 14.7 231 191
MIPS R12000 400 MHz 1998 24.2 43.5? 320 319
DEC Alpha 21264 500 MHz 1998 27.3 57.7 311 382
MIPS R14000 600 MHz 2001 483 499
Sun UltraSPARC III 1 GHz 2001 511 688
IBM POWER4+ 1 GHz 2003 617 862
DEC Alpha 21364 1 GHz 2001 689 975
AMD Athlon XP 2.2 GHz 2002 1080 873
Intel Xeon 2.8 GHz 2003 1249 1081
AMD Opteron 250 2.5 GHz 2004 1619 1652
Typical SPEC scores on HP Itanium computers
Processor Clock Year SPEC95
int  fp		 SPEC2000
int  fp
Itanium Merced 800 MHz 2001 365 610
Itanium McKinley 1.0 GHz 2002 807 1422
Itanium Madison 1.5 GHz 2003 1315 2106

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Documentation

Most of the SPEC scores are from official SPEC results websites, now archived. Some scores are from vendor product pages, now also archived or lost.

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