However my main question is really, why should the same query now run slower on a dual-core system than on a single-core?

然而我的主要问题是，为什么同一个查询在双核系统上比在单核上运行得慢？

youdao

It can be run on up to two dual-core CPU servers, with up to 4 GB of memory, any storage system setup, and no database size restrictions — or any other types of artificial restrictions.

它可以运行多达两个双核CPU服务器、多达4 GB的内存、任何存储系统设置，而且无任何数据库大小限制和其他人为限制。

youdao

A check that I do quite often is to ascertain the quantity of processors on the system. So, if I have purchased a dual processor quad-core server, I can run.

我经常做的检查是确定系统中处理器的数量。

youdao

Obligingly, Samsung have provided a handy comparison chart by shipping its first wave of Galaxy S III devices to the US with a dual-core Snapdragon S4 processor and internationally with a quad-core Samsung Exynos system-on-chip.

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HP's newest 11.6-inch not-quite-a-netbook (or a notbook as we like to call it) is the first Fusion system to hit the market, and with a dual-core 1.6GHz E350 Zacate processor and AMD Radeon HD 6310 GPU on the same chip it promises... well, everything AMD has promised for so long.

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It will be a sleek 9mm wide (.35 inches), a hair wider than the iPhone 5's 7.6mm (.3 inches), and run the latest version of Google's Android operating system, Jelly Bean, with a 1.7 Ghz dual-core processor.

CNN: Samsung to make a mini version of its Galaxy S4