The HP Superdome is a high-end server computer developed and produced by Hewlett-Packard. The latest version of product, "Superdome 2" was introduced in 2010. Superdome 2 scales from 2 to 32 sockets (up to 128 cores) and 4 TB of memory. When introduced in 2000, the Superdome used PA-RISC processors. Since 2002, there has been another version of the machine based on Itanium 2 processors, marketed in parallel as the HP Integrity Superdome. The classic PA-RISC Superdome was subsequently rebranded to HP 9000 Superdome. The predecessor to the Superdome was the HP V-Class (which was based on a design acquired from Convex).
The new HP Integrity Superdome 2 utilizes the Intel Itanium 93xx-series microprocessor, otherwise known as "Tukwila" and is totally redesigned with parts from the HP BladeSystem C7000 enclosure. Since 2012 Intel Itanium 95xx microprocessor Poulson are available too.
Superdome usually runs the HP-UX operating system, although the Itanium 2 version is also compatible with many other systems, for example with Microsoft Windows Server 2008 R2, SUSE Linux Enterprise Server, Red Hat Enterprise Linux, Debian Squeeze, and OpenVMS V8.2-1.
The Superdome comes in four different generations :
- Legacy (Only PA-RISC cells)
- SX1000 (Can mix both Itanium and PA-RISC cells, but not in the same partition)
- SX2000 (Can mix both Itanium and PA-RISC cells, but not in the same partition)
- SX3000 (Blade based with only Itanium 93xx-series blades)
Architecture (SX1000 version)
A building block is a cell, a card holding 4 processors and memory. Superdome has a ccNUMA architecture, which means that processors have shorter access times for their cell's memory but longer access times for other cell's memories, and data items are allowed to be replicated across individual cache memories but are kept coherent with one another by cache coherence hardware mechanisms. In this case, a directory-based coherency mechanism is employed. 
A center of each cell is an ASIC called cell controller (CC), that connects to four processor sockets (providing an average of 1.6 GB/s of bandwidth per socket), to four local memory subsystems, and to the backplane. The CC itself contains a crossbar, and four CCs interconnect via a second-level crossbar. In maximum machine's configuration four second-level crossbars interconnect with each other, supporting in total 64 processor sockets.
Each socket may hold either a single-core PA-RISC processor (PA-8600 or PA-8700), or a dual-core PA-RISC processor (PA-8800 or PA-8900), a single-core Itanium 2 processor, two Itanium 2 processors (using the mx2 module), or one dual-core Itanium 2 processor. There are almost no architectural differences between PA-RISC and Itanium versions of Superdome.
Each CC connects to one local I/O controller (an SBA), which in turn may connect to a single I/O card cage (also called I/O chassis) with 12 PCI-X slots. Maximum 192 slots[clarification needed] are possible for the Legacy and SX1000. It is not possible to expand the number of I/O slots for a cell.
Superdome is not mounted on a standard rack, it is instead shipped as either one or two dedicated cabinets. One cabinet scales up to 8 cells.
Architecture (SX2000 version)
The architecture of the SX2000 is highly similar at first glance compared to the SX1000, however it has quite a few design differences.
- The hardware clock has been moved from the power-board to the backplane and doubled up for redundancy and greater quality.
- The SX2000 introduced PCI-Express card cages (retaining support for PCI-X 2.0). Maximum of 192[clarification needed] external slots are possible.
- All connections have been changed to high speed serial (HSS) connections for greater speed and greater redundancy.
- Three crossbars compared to two crossbars in each quadrant (per four cells) for greater speed.
Similarly to both Legacy and SX1000 setups, SX2000 can be:
- 16-way (four cellboards and two IO-cages can be used)
- 32-way (eight cellboards and four IO-cages can be used)
- 64-way (expands the one cabinet to two-cabinet complex, with 16 cells and eight IO-cages)
Superdome supports nPars (hard partitions), that are granular on the level of a whole cell (and its I/O card cage), this means that a maximum of 16 cells can be part of a nPar.
The Superdome also supports vPars (virtual partitions), granular on a single core level and a single PCI slot level, this means that a top level nPar can house several vPars to better utilize the hardware in the Superdome.
Architecture (SX3000 version)
The currently available options for SX3000 are:
- 8s (maximum 8 blades, max 4 blades per partition)
- 16s (maximum 8 blades, max 8 blades per partition)
- 32s starter (maximum 16 blades, max 16 blades per partition, shipped as double 16s enclosures that can be configured as a SX3000 32s using the starter package upgrade kit)
- 32s (maximum 16 blades, max 16 blades per partition)
For the SX3000 there are four integrated 10 Gbit ethernets per blade. In addition, maximum of 96 external PCI-e ports are available. It is unsupported to install any mezzanine cards, although three free slots exist on each blade.
- "HP Showcasing Itanium-based Superdome Server". HP. Dec 9, 2002. Retrieved 2008-03-29.
- "Windows Server 2008 R2: System Requirements". Microsoft.com. Retrieved 2011-06-15.
- Certification – Integrity Superdome https://hardware.redhat.com/show.cgi?id=166854
- "HP Showcasing Itanium-based Superdome Server Running HP-UX, Windows and Linux Concurrently" (Press release). The Hewlett-Packard Company. 2005-01-17. Archived from the original on 2008-10-02. Retrieved 2008-10-02. "The full line of HP Integrity servers featuring the new Intel Itanium 2 processors is now available with support for HP-UX 11i v2, Microsoft Windows Server 2003, OpenVMS and Linux operating systems."
- "1 Introduction" (pdf). HP OpenVMS Version 8.2–1 for Integrity Servers New Features and Release Notes. Palo Alto, CA, USA: Hewlett-Packard. September 2005. pp. 1–1. HP Order Number BA322-90033. Archived from the original on 2008-10-02. Retrieved 2008-10-02. "Major new features include: • Support for the following Integrity server platforms: — HP Integrity rx7620 server — HP Integrity rx8620 server — HP Integrity Superdome server"
- van der Steen, Aad J.; Jack J. Dongarra. "Overview of Recent Supercomputers" (14 ed.). Retrieved 2008-03-29.
- Asghar, Ghori (2007). HP Certified Systems Administrator (2nd Edition). pp. 132–136. ISBN 1-4243-4231-7.