前にもアップデートされたと思ったんですが、またアップデートされていますね。
ver1.56になりました。
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> VERSION 1.56 HIGHLIGHTS
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> ========================================================
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> *1291300062* Arma 2: Private Military Company Lite - all units, vehicles and weapons from Arma 2: Private Military Company are included in this patch with lower quality textures and audio files. The full version of Arma 2: Private Military Company with high resolution textures and packed with a new campaign is available for purchase; see http://www.arma2.com/pmc for more information about the content of Arma 2: Private Military Company.
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> *1291300063* ARMEX - The Multiplayer Armory - enables you to try out all weapons and every single vehicle model from Arma 2 in dynamically generated missions with up to eight friends online or over LAN!
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> Version 1.55-1.56 Changelog
>
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> Data
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> ----
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> *1291300064* Add: more camo (replaceable textures) selection for OA vehicles.
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> *1291300065* Fixed: missing shadows and heads in distance LODs for some OA characters.
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> *1291300066* Added: MP Armory.
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> Engine
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> ------
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> *1291300067* Improved: -exThreads=3 now default for dual cores.
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> *1291300068* Improved: -cpuCount defaults improved for 6 or more than 8 CPUs.
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> *1291300069* Fixed: No more LOD blending issues (esp. with vegetation).
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> *1291300070* Fixed: Ignored collision with some vehicles.
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> *1291300071* Improved: AI cover selection improved a bit.
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> *1291300072* New: Video options VSync selection.
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> *1291300073* Fixed: Character collisions with stones often resulted in flying or being stuck. ([http://dev-heaven.net/issues/12043](http://dev-heaven.net/issues/12043))
デュアルコアCPUに最適化されたりとかされてるみたいですね。英語は苦手なので参ります。なんか某所では1.56にすると軽くなったという話もありますし、アップデート終わったら試してみましょう。めちゃくちゃでかくてなかなか進みません。