Hitachi SR2201/1024

Also known as SR2201/1024

Operated by University of Tokyo at University of Tokyo Computer Centre .

Phase 1 seed dataset, compiled by hand. These rows were built from public operator, laboratory and vendor sources. A mechanical second-reader pass has since fetched every cited source: 1092 of 1153 systems have a readable citation that names them, and 40 are genuinely weakly sourced. Every claim carries its source and a confidence tier. Treat anything below verified as a lead, not a citation.

Measured performance

Rmax: 220.4 GFlop/s
Rpeak: 307.2 GFlop/s
Rmax ÷ Rpeak: 71.7%
Cores: 1,024
Power: -
Per watt: - GF/W

Figures are as last publicly reported for the configuration described below, not a live measurement. Where a system was upgraded in place, the post-upgrade configuration is shown and the earlier one appears in the timeline.

What this machine is made of

One row per supplier relationship. “Supplier at build” is the company that shipped the part at the time; where that company has since been acquired, the parent it rolls up to today is shown beside it. That distinction is what makes ticker-level aggregation possible across a thirty-year dataset.

Role	Part	Supplier at build	Quantity	Confidence	Source
Integrator	- Hitachi SR2201	Hitachi 6501TSE	-	Reported	top500.org top500.org
CPU	Hitachi SR2201 processing unit CPUs PA-RISC 1.1 · 1C · 0.15 GHz Hitachi SR2201 PU (HARP-1E 150MHz)	Hitachi 6501TSE	1,024 reported	Reported	top500.org top500.org
Interconnect	Hitachi 3D hyper-crossbar Interconnect 3D hyper-crossbar · 300 MB/s point to point Hyper crossbar	Hitachi 6501TSE	-	Reported	top500.org top500.org
Operating system	Hitachi HI-UX/MPP Operating systems Unix (Mach 3.0 microkernel), Hitachi-customised · Proprietary HI-UX/MPP	Hitachi 6501TSE	-	Reported	top500.org top500.org

The read

The second Japanese university, after none before it, to hold the outright top position: Tokyo led the June 1996 list six months before Tsukuba's CP-PACS, built on the same Hitachi SR2201 line, took over in November 1996. Both machines ran the same processor, HARP-1E at 150MHz, and the same hyper-crossbar fabric; the difference was scale, 1,024 nodes against 2,048. Reading the two together says something the ranking alone does not: a single vendor's product line, sold to two different academic buyers within one calendar year, briefly held the top of the world's list twice in succession. No public source states when the University of Tokyo retired this system, so the field is left blank rather than guessed.

Timeline

1996 First operational source
1996-06 List debut at #1 (June 1996) source

Public list appearances

Pointers only: rank and edition, linking to the canonical entry. We do not reproduce list tables. See sourcing policy.

#1: TOP500, June 1996 →

Site & facility

University of Tokyo Computer Centre

Location: Tokyo, Japan
Commissioned: 1996

top500.org top500.org

Source check

We fetched this system's own citations and recorded whether each page actually mentions it. This is a corroboration signal, not a fact check, and it is published so you can see how well the sourcing holds up rather than take it on trust.

Cited source	Result	Found on the page
top500.org	names system, part and count	Hitachi SR2201 processing unit, Hitachi 3D hyper-crossbar, Hitachi HI-UX/MPP · counts: 1024
top500.org	names system, part and count	Hitachi SR2201 processing unit, Hitachi 3D hyper-crossbar, Hitachi HI-UX/MPP · counts: 1024

Checked 2026-10-09 by pnpm verify. Re-run it and the table changes with the web.