ECMWF Cray XC40

Also known as ECMWF Reading Cray HPCF; Cray XC40 (Reading)

Operated by ECMWF at ECMWF Data Centre (Reading) .

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: 3.94 PFlop/s
Rpeak: 4.25 PFlop/s
Rmax ÷ Rpeak: 92.7%
Cores: 126,468
Power: 1.90 MW
Per watt: 2.1 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	- Cray XC40	Cray HPENYSE rolls up to Hewlett Packard Enterprise	-	Reported	top500.org
CPU	Intel Xeon E5-2695 v4 CPUs x86-64 · 18C · 2.1 GHz · 14 nm · 120 W Intel Xeon E5-2695v4 18C 2.1 GHz	Intel INTCNASDAQ	-	Reported	top500.org
Interconnect	Cray Aries Interconnect Dragonfly · About 10 GB/s per direction · Around 1 microsecond Cray Aries interconnect	Cray HPENYSE rolls up to Hewlett Packard Enterprise	-	Reported	top500.org
Operating system	Cray Linux Environment Operating systems Linux, Cray-customised · Proprietary layer over open-source Linux Cray Linux Environment	Cray HPENYSE rolls up to Hewlett Packard Enterprise	-	Reported	top500.org

The read

ECMWF's Cray high-performance computing facility in its Reading data centre, listed on TOP500 as a Cray XC40 with Xeon E5-2695v4 18C 2.1 GHz and the Aries interconnect: 126,468 cores, 3.94 PFlop/s Rmax, 4.25 PFlop/s Rpeak and 1,897 kW, ranked 18 in June 2016 and 137 in November 2022 (the same TOP500 entry also carries earlier 2014 to 2015 rankings from an XC30-era configuration with 83,160 cores). ECMWF's migration notice says all operational forecasting moved from Reading to the new Bologna data centre on 18 October 2022, after which the Cray HPCF and its filesystems were unavailable from 1 November 2022 and shut down by the vendor. Its successor is the Atos system recorded as ECMWF HPCF-AA. A twin XC40 cluster in the same facility is not recorded separately.

Timeline

2016 First operational source
2016-06 List debut at #18 (June 2016) source
2022-11-01 Decommissioned source

Public list appearances

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

#18: TOP500, June 2016 →

Site & facility

ECMWF Data Centre (Reading)

Location: Reading, United Kingdom

top500.org confluence.ecmwf.int

Change history

2026-10-02 Added ECMWF Cray XC40

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
confluence.ecmwf.int	names system only	-
top500.org	names system and part	Intel Xeon E5-2695 v4, Cray Aries, Cray Linux Environment

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