PA-RISC information - since 1999

HP N4000 (rp7400)

Quick Facts
Introduced 1999-2001
Period Maturity (III)
CPU 1-8 PA-8500/
1-8 PA-8600/
1-8 PA-8700
360-750 MHz
Caches 1.5-2.25 MB L1
Design Stretch
Drives 2 SCSI
Expansion 12 PCI
Bandwidth System 4.2 GB/s
CPU 17 GB/s
Mem 8.5 GB/s
I/O 6.4 GB/s
XBAR 15.3 GB/s
3 serial
100E console

The HP 9000 rp7400 were mid-range PA-RISC servers and the original HP 9000 N-Class N4000 from the turn of the century. The original N4000 (rp7400) is based the Stretch system architecture, also used in the L1500 and L3000 (rp5430/rp5470) servers. Later rp7405 and rp7410 servers were also labeled N4000 and feature a similar set of I/O options and expandability in basically the same chassis, with a completely different system architecture, the Cell.

N4000s were shipped in two models with different system boards: A3639A and A3639B. The N4000 that was later renamed as rp7400 was shipped with an even different mainboard with the model number A3639C.

Model rp Product Introduced Price
N4000 A3639A
1999 $48,000
rp7400 A3639C 2001

The original N4000 (A3639A and A3639B) and later rp7400 (A3639C) are in fact different products, based on the same basic architecture but with differences relating to the type and number of processors.

System architecture


The rp7400 N4000 supports one to eight processors, designated by the [-36, -44, …, -7X] suffix. Not all of the earlier N4000 support the later processors and the maximum number of CPUs.

Model Suffix CPU Speed L1 Cache
N4000 A3639A -36
1-? PA-8500
1-? PA-8500
360 MHz
440 MHz
512/1024 KB on-chip
512/1024 KB on-chip
N4000 A3639B -36
1-? PA-8500
1-? PA-8500
1-? PA-8600
360 MHz
440 MHz
550 MHz
512/1024 KB on-chip
512/1024 KB on-chip
512/1024 KB on-chip
rp7400 A3639C -36
1-8 PA-8500
1-8 PA-8500
1-8 PA-8600
1-8 PA-8700
1-8 PA-8700
360 MHz
440 MHz
550 MHz
650 MHz
750 MHz
512/1024 KB on-chip
512/1024 KB on-chip
512/1024 KB on-chip
768/1536 KB on-chip
768/1536 KB on-chip

Itanium 2/IA64 processors were planned on the N4000 but apparently never offered.


The rp7400 system is based on the Stretch chipset, used in the L1500 and L3000 (rp5430/rp5470) servers as well. Stretch has four main components:

  1. Prelude memory controller, is the main crossbar of the system
  2. Four DEW Runway converters, attach the processors to the main buses
  3. Two IKE I/O controllers connect the PCI bridges via I/O channels
  4. 14 Elroy PCI bridges (LBAs) convert the IKE I/O to PCI buses

The rest of the system is implemented with common parts:

» View a system-level illustration (ASCII) of the N4000’s system/bus architecture.

System buses

The system bus architecture provides more bandwidth than could be used under practical circumstances. The designers probably counted on future CPU upgrades, such as Itanium.


Expansion slots


External ports

Operating systems


Model SPEC2000, int SPEC2000, fp SPEC2000
rate, int
rate, fp
493 489 5.7
2-CPU: 11.3
4-CPU: 22.1
8-CPU: 42.6
2-CPU: 10.4
4-CPU: 19.3
8-CPU: 30.5
551 524 6.4
2-CPU: 12.5
4-CPU: 24.6
8-CPU: 46.7
2-CPU: 11.0
4-CPU: 20.5
8-CPU: 32.1



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