Comments on: Blue Gene/L tops its own supercomputer record

Blue Gene/L already is the world's fastest supercomputer, according to the Top500 list that ranks such machines.

[multimediavt]

Wrong processor count ...

I believe this article is in error if the system has reached it's
complete 64 compute rack size.

BlueGene/L has 1024 dual processor nodes per rack, or 2048
processors per rack. The article states this incorrectly as '1024
processors per rack'. The total processor count should be
131,072, if this is the full 64 rack system.

Please feel free to verify this with IBM.

Jason Lockhart
Assoc. Director,
Virginia Tech Terascale Computing Facility

[alpha754293]

Wrong Processor Count

The processor count IS correct - it's the number of cores per die that is in question.

Each of the PowerPC 400 700 MHz processors are dual-core, with a shared 4MB L3 cache architecture, so it is 65,536 processors, and 131,072 cores.

The dual-core architecture also implies that single core PowerPC 400 processors are NOT available.

[Shankland]

Reporter responds: it's a definitional issue

Most server makers these days define a processor as that which plugs into a socket, not as a processor core. There are significant exceptions, and IBM is one of them, though it's not consistent.

IBM, which led the server world to the dual-core world with its Power4, says a dual-core chip has two processors. Sun, Hewlett-Packard, Intel, AMD, Microsoft, BEA Systems, VMware and others say a dual-core chip is one processor. News.com goes with the socket definition (though we, too, were in flux for some time). So if you were to buy a new PC with a dual-core Pentium or Athlon, for example, you wouldn't call it a dual-procesor system even though of course it behaves as such in many ways.

The issue gets particularly complicated with some more radical multicore approaches. For example, Sun's Niagara chip has eight cores, and each core can execute four threads, so from a software point of view it looks like 32 processors. Do you call Niagara a single processor, or eight, or 32? And how about Azul Systems' Vega, which has 24 cores but runs Java code rather than a conventional operating system--is it a single processor or 24?

Worse, many software companies charge per processor, but the definitions vary. IBM itself is conflicted; when describing the dual-core Power4 and Power5 chips, it calls each chip two processor--but it labels the dual-core Xeon and Opteron one processor (see http://news.com.com/IBM+shifts+software+price+for+dual-core+x86+chips/2100-1006_3-5679679.html). Oracle counts each core on a multicore chip as three quarters of a processor for softwre licensing purposes, so software for a dual-core chip would cost 1.5 times that for a single-core chip.

Regarding Blue Gene, the computer has 65,536 nodes, each node with a single chip. Each chip has two PowerPC 440 processor cores. So if you're counting by chips, it's 65,536, by cores, twice that. IBM tends to use the "processor = core" definition in its literature, which accounts for the discrepancy with the story.

[multimediavt]

Wrong processor count ...

I believe this article is in error if the system has reached it's
complete 64 compute rack size.

BlueGene/L has 1024 dual processor nodes per rack, or 2048
processors per rack. The article states this incorrectly as '1024
processors per rack'. The total processor count should be
131,072, if this is the full 64 rack system.

Please feel free to verify this with IBM.

Jason Lockhart
Assoc. Director,
Virginia Tech Terascale Computing Facility

[alpha754293]

Wrong Processor Count

The processor count IS correct - it's the number of cores per die that is in question.

Each of the PowerPC 400 700 MHz processors are dual-core, with a shared 4MB L3 cache architecture, so it is 65,536 processors, and 131,072 cores.

The dual-core architecture also implies that single core PowerPC 400 processors are NOT available.

[Shankland]

Reporter responds: it's a definitional issue

Most server makers these days define a processor as that which plugs into a socket, not as a processor core. There are significant exceptions, and IBM is one of them, though it's not consistent.

IBM, which led the server world to the dual-core world with its Power4, says a dual-core chip has two processors. Sun, Hewlett-Packard, Intel, AMD, Microsoft, BEA Systems, VMware and others say a dual-core chip is one processor. News.com goes with the socket definition (though we, too, were in flux for some time). So if you were to buy a new PC with a dual-core Pentium or Athlon, for example, you wouldn't call it a dual-procesor system even though of course it behaves as such in many ways.

The issue gets particularly complicated with some more radical multicore approaches. For example, Sun's Niagara chip has eight cores, and each core can execute four threads, so from a software point of view it looks like 32 processors. Do you call Niagara a single processor, or eight, or 32? And how about Azul Systems' Vega, which has 24 cores but runs Java code rather than a conventional operating system--is it a single processor or 24?

Worse, many software companies charge per processor, but the definitions vary. IBM itself is conflicted; when describing the dual-core Power4 and Power5 chips, it calls each chip two processor--but it labels the dual-core Xeon and Opteron one processor (see http://news.com.com/IBM+shifts+software+price+for+dual-core+x86+chips/2100-1006_3-5679679.html). Oracle counts each core on a multicore chip as three quarters of a processor for softwre licensing purposes, so software for a dual-core chip would cost 1.5 times that for a single-core chip.

Regarding Blue Gene, the computer has 65,536 nodes, each node with a single chip. Each chip has two PowerPC 440 processor cores. So if you're counting by chips, it's 65,536, by cores, twice that. IBM tends to use the "processor = core" definition in its literature, which accounts for the discrepancy with the story.

[Lolo Gecko]

my abacus has 128K beads ...

go figure :)

[Lolo Gecko]

my abacus has 128K beads ...

go figure :)

[56455734]

Blue Gene/L ASIC

Why don't they upgrade the L1 D-cache & L1 I-cache of the 440 core ?

or "Can they upgrade the... ?"

[56455734]

Blue Gene/L ASIC

Why don't they upgrade the L1 D-cache & L1 I-cache of the 440 core ?

or "Can they upgrade the... ?"