The Codex is a list of quickly jotted-down notes related to less widely-known computer systems – especially Japanese systems – and may help provide context for posts on Kira Ops.



  • GS21 is Fujitsu’s line of S/390 clone mainframes. These consist of inhouse-designed /390-compatible processors and custom operating systems. The processors appear to have very similar specs to Fujitsu’s SPARC64 VII chips, with four cores and 6MB of L2 cache, and were released around the same time; they also appear together on roadmaps. This leads me to believe that it’s possible that they’re both layers on top of a similar underlying core. These also appear to be the same processors that are used in Fujitsu’s BS2000 mainframes for the German market. These systems run a choice of two operating systems. MSP is Fujitsu’s equivalent to MVS, while XSP is similar to VSE. As far as I can tell, the GS21 line is marketed primarily to the Japanese market, although it may have a few customers in Australia. GS21 is probably a 31-bit system, with application address spaces limited to 2GB each. The lower-end operating system – XSP – also runs on Xeon-based Primequest 1000 systems.
  • BS2000 is a mainframe operating system for the German market. It originated at RCA in the early 70′s, and has passed through the hands of Siemens, Fujitsu-Siemens, and finally Fujitsu. It runs on S/390 compatible hardware, probably identical to the GS21 mainframes mentioned above, but is substantially different at the software level; while GS21 systems are highly similar to IBM OS’s, BS2000 is completely distinct. BS2000 is commonly used among German companies and government agencies, and in the past has had very good software support, including regular releases of Oracle for BS2000. It also has the dubious distinction of running on more platforms than perhaps any other mainframe operating system, with hardware built on S/390 (S-series mainframes, currently produced), x64 (SQ-series mainframes, currently produced), SPARC (SX-series mainframes, probably EOL in late 2010), and MIPS (SR-series mainframes, probably EOL’d between 2004 and 2006.) All of these systems support some degree of logical partitioning, including support for Windows or Linux (on the SQ series), Reliant UNIX (on the SR-series), and Solaris (on the SX-series) as operating systems in partitions. There’s also a virtual machine platform called VM2000 that seems to purely work with BS2000 guests, and is probably similar to IBM VM. Like GS21, BS2000 hardware appears to be 31-bit, with application address spaces limited to 2GB each.
  • VME is a mainframe operating system formerly owned by ICL, almost exclusively (but widely) used in the UK. During the early 2000′s, it was gradually shifted from a standalone mainframe product to an emulator running on specially-designed x86 “mainframes,” then again to a pure software product licensed for use on certified third-party servers. Although VME is unlikely to get new customers or new hardware, it retains a large installed base, and Fujitsu has announced that it intends to continue VME support for several years.
  • SXO is a high-reliability mainframe-like system for Fujitsu’s SureSystem 7000 telecom computers. It’s derived from the TRON Project‘s CTRON operating system. Fujitsu categorizes SureSystem as a GS21-family mainframe, but it’s distinct in both CPU architecture and operating system.


  • VOSK and VOS1 are Hitachi’s low-end mainframe systems. Details on these are spotty, but they’re probably roughly equivalent to VSE. They run on a mainframe called the AP7000, which is based on IBM Power processors, but neither OS apparently supports SMP, and both have highly limited address space (512MB for VOS1, 2GB for VOSK.) These are exclusively for the Japanese market, and probably only for legacy customers.
  • VOS3 is Hitachi’s high-end S/390-compatible 64-bit mainframe operating system cloned from MVS, running on a system called the AP8800E and utilizing custom processors. The AP8800 appears to support up to 8 instruction processors and 8 I/O processors. These appear to use a custom (non-z/Architecture) 64-bit extension, specific to Hitachi, and support up to 64GB of memory. Hitachi also appears to offer another line of mainframes, the MP5600, which supports both VOS3 and VOS1 workloads, but it’s a legacy model.


  • ACOS-2 is NEC’s low-end mainframe OS; it’s supposedly derived from GCOS 4, which was a minicomputer OS developed by Honeywell in the 80′s. The modern ACOS-2 mainframe – the i-PX7300W – uses Intel Xeon processors, and probably reasonably fast ones (although no specific model is specified), but appears to have an address-space limitation of 256MB. This is obviously a legacy operating system.
  • ACOS-4 is NEC’s higher-end mainframe line, derived from GCOS 7 (a Honeywell mainframe system.) Until recently, ACOS-4 ran on Itanium-based hardware, apparently with up to 48 cores; it’s not clear whether this indicates a 24-socket or 48-socket system, although I suspect the former. Only 32 processors are supported in a single OS instance, with LPAR’s required in order to use more than 32 processors. These machines support up to 32GB of RAM. Additionally, they can run HP-UX, which implies that they may consist of a certain amount of rebranded HP Integrity hardware. In mid 2012, NEC announced a return from IA64 to the previous NOAH line of proprietary mainframe processors, now produced in a quad-core variant on 40nm, called NOAH-6.
  • ACOS-6 was a high-end GCOS 8 derivative, EOL’d a few years ago. It only ever ran on proprietary NEC processors.


  • GCOS 7 is the lower-end of Bull’s two operating systems. It was developed by Honeywell in the 70′s and 80′s, and probably bears some filial relationship to Multics. Recently moved from a mix of Itanium and low-end x86 hardware to new Xeon-E7-based servers. GCOS 7 can only address 1GB of RAM.
  • GCOS 8 is the higher-end Bull mainframe operating system. It’s based on General Electric’s GECOS system, which slightly predated Multics, and bears roughly no relation to GCOS 7. GCOS 8′s hardware is considerably more robust than the options for GCOS 7; Bull’s Novascale GCOS 8 machines support up to 32 Itanium 9500 cores, divided into up to four logical partitions (at least one has to be Linux.) GCOS 8 can address up to 28GB of RAM per partition. Like GCOS 7, it can use an external database as a backend for GCOS applications.


  • Clearpath Libra 48-bit, runs the MCP operating system, performance-competitive with IBM in some segments. Low-end systems are Intel-based, high-end systems are custom CMOS. Custom CMOS systems are being phased out in the near future – Unisys claims that Xeon machines have reached performance parity.
  • Clearpath Dorado 36-bit, runs the old Sperry/Univac OS 2200 system, commonly used by airlines and by the US government (the IRS operates at least two maxed-out Dorado systems.) Similar performance characteristics to the Libra. CMOS processors are probably microcoded and architecturally very similar between Libra and Dorado. Entry boxes are Intel-based. Multiple Dorado systems, regardless of architecture, can be clustered with the XPC-L record lock processor.


Note that for Japanese systems, the term “Office Computer” is more common than “minicomputer.”

  • Mitsubishi Centrage is Mitsubishi’s minicomputer line, and it appears to be a distant relative of the MELCOM-81 mini from the late 60′s. The current iteration is Centrage II, which is a rebranded Stratus/NEC ftServer. It runs a minicomputer OS called DP-UX that implements minicomputer features such as a record-based filesystem on top of a UNIX core.
  • Fujitsu ASP is Fujitsu’s minicomputer operating system, running on an x64-based server line called Primergy 6000. Additionally, ASP is supported on the Xeon-based PrimeQuest 1000, along with Fujitsu’s VSE and VM equivalents (XSP and AVM, respectively.) It appears strongly similar to IBM i and has a BSD-based POSIX subsystem called UXF. Previously, this OS ran on the brilliantly named GRANPOWER 6000.
  • NEC A-VX02 is a really great name for an operating system, and runs on a whole range of NEC PC-compatible servers from tiny Celeron systems to cabinets. It seems to run only as an emulated platform on top of Windows, but in the early 90′s also ran on custom NEC CPU’s.


  • SPARC64 fx is the designation for a family of Fujitsu SPARC-derived parts with no SMP support (only using a custom cluster interconnect) and an emphasis on wide vector processing using custom Fujitsu-only extensions. Without the extensions, the cores themselves resemble underclocked versions of the SPARC64 VII with a significantly shrunken L2 cache and no SMT. Historically, due to the extensions and the heavily custom nature of these parts, I’ve been reluctant to designate them as actual SPARC; however, the extensions (HPC-ACE) have now been incorporated into a bona fide commercial SPARC64 chip, the SPARC64 X. As far as I know, they remain Fujitsu-specific and not part of an official SPARC ISA spec. Future SPARC64fx platforms will use Micron’s Hybrid Memory Cube high-bandwidth memory technology.
  • NEC SX is NEC’s family of high-performance vector computers. SX-9 (single core, 3.2GHz, 32 FLOPS/core/cycle, 102.4GFLOPS per socket) has been superseded by the SX-ACE, also designated NGV (“Next Generation Vector”), which has 4 cores, runs at 1GHz, and executes 64 FLOPS/core/cycle for a cumulative 256GFLOPS per socket. Notably, memory bandwidth remains at 256GB/s in SX-10 as in SX-9, but NEC apparently expects the negative effects of increasing core performance without increasing bandwidth to be minimized by the combination of lower clock and a larger cache (increased from 256KB per core in SX-9 to 1MB per core in SX-10.)