主题：【文摘】E3 PS3和Xbox360机能深度对比分析 -- 大卫

转载自XBOX-360.cn,作者：叉包饭斯DKCK

中文独家首发：XBOX-360.cn

　　(时间比较仓促，涉及硬件专业领域的术语如有误译，请各位包涵、指正！)

　　中央处理器CPU

　　Cell (1个PowerPC核心 + 7个以 3.2 GHz 频率运作的协同处理器) |X360 Cpu (3个PowerPC核心)

　　X360核心的优势和不足

　　- 为三个同步核心编程要比对一个处理器编程容易许多

　　- 强劲的单线程表现，但只能运行在受限制的线程数下

　　- 多线程编程比较困难，但远远没有为Cell编程困难

　　- 最好的概括就是：是个“条条大路通罗马”的解决方案。

　　Cell核心的优势和不足

　　- Cell是一颗强劲的平行向量处理器

　　- 在运行多重浮点运算任务时表现出色(如游戏引擎、视频编码解码等)

　　- 编程困难――所有的软件必须做特别优化

　　- 单线程表现糟糕

　　- 没有硬件的分支预警结构，在运行复杂的分支运算时表现尤其糟糕(如人工智能代码)

　　- 高度专业化的解决方案，Cell是第一颗也是最重要的一颗多媒体处理器，非常适合HDTV和游戏主机的应用。是个两极分化的核心――在运行游戏引擎方面非常强；但在人工智能编码方面非常弱。

　　显示核心GPU

　　参考：今天最高端的6800ultra级显示核心拥有16条像素渲染管线，和6条阴影渲染管线，总共222百万个晶体管。

　　X360的优势和不足

　　- ATI的下一代GPU (即R500) 拥有独特的架构――统一的顶点、阴影和像素渲染引擎。拥有48条统一的引擎，会自动分配具体的功能。

　　- 更容易编程，不过理论上峰值较独立的渲染管线有所降低。

　　- 10MB的帧缓冲，允许“自由的”反锯齿效果，但限定在720p的分辨率上。

　　- 晶体管数量未知

　　PS3 GPU的优势和不足

　　- 官方声称拥有300百万个晶体管，和改进的像素和顶点渲染管线。具体数目未知。从6600GT的160白万个晶体管到6800ultra的222百万个――可以推测，PS3的GPU拥有24条像素渲染管线和大约10～12条阴影渲染管道。有理由相信PS3的GPU将两倍强大于6800Ultra的能力。

　　- 独立的渲染管线运行更快但难以编程。

　　内存Memory

　　X360

　　512MB统一的DDR3内存，GPU和CPU共享。 灵活性是其显著的优势。缺点是两者不得不共享。游戏开发者可以按照爱好自由地分配，如五五开或三七开等等。

　　PS3

　　Cell有256MB XRD

　　GPU有256MB DDR3

　　优势在于每个核心都有独立的内存，速度更快，但都限制在256MB。而X360最大可以达到512MB，但Cell只能止步于256MB。

　　带宽Bandwidth

　　X360

　　• 22.4 GB/s 内存界面带宽

　　• 256 GB/s EDRAM 内存带宽

　　• 21.6 GB/s 前端总线

　　10MB的帧缓冲，256GB/s的带宽是X360GPU的主要优势；这意味着R500不会被带宽所限制，允许自由的反锯齿和其他影像特效。但代价就是写实般的画面只能限定在720p。再向上只能减帧

　　开发者应该有变通的办法。就像原来的PS2限制在4MB帧缓冲上；而NGC则只有2MB帧缓冲。

　　PS3

　　主内存 25.6GB/s

　　VRAM 22.4GB/s

　　RSX 20GB/s (写) + 15GB/s (读)

　　SB< 2.5GB/s (写) + 2.5GB/s (读)

　　相当标准。

　　视频输出Video Output

　　X360

　　一个DVI输出端口，支持所有的HD(高清晰)分辨率(包括1080p和1080i)。注意大部分游戏很可能都运行于720p下，减帧运行于1080p下。就像GT4在PS2上那样。

　　PS3

　　两个HDMI端口 (写保护DVI、音频联合接口) ，因此可以连接两台HDTV。HDMI是个全新的接口。

　　但是，如果你真的想这么做，那么不得不让同一款游戏在1080p下运行于一台电视上，另一台电视的分辨率只能达到720p。

　　其他的都是浮云……The rest are extras

　　以下所有的功能只会增加成本，对游戏本身的提升毫无帮助。PS3这方面显得尤其臃肿：

　　两个以太网接口

　　内建Wi-Fi

　　蓝牙

　　多种闪存接口(SD、记忆棒等)

　　蓝光光驱

　　以上PS3增加的功能，全部加起来要有100美刀。

　　结论

　　X360和PS3的机能在同一水平上，只是在设计思想上的解决方案不同。

　　X360机能烧弱，但更加灵活，易于编程；PS3理论上更为强劲，但灵活性不佳，也难以编程。

　　原文如下：

　　引用:

　　----------------------------------------------------------------

　　CPU: Cell (1 PPC + 7 units) vs X360 Cpu (three PPC cores)

　　X360 advantages and disadvantages

　　- much easier to program for 3 symmetric processors than an asymmetric processor

　　- strong single thread performance, but can only run limited number of threads

　　- multithreading is difficult to program for but NO WAY near as hard as for the cell

　　- Best described as a jack of all trades approach

　　Cell Advantages and disadvantages

　　- The cell is a massively parallel vector processor

　　- excellent for running multiple floating point tasks such as (game engine, encoding and decoding video)

　　- Difficult to program for -- ALL software has to be optimized

　　- Poor single thread performance

　　- NO hardware Branch prediction, Extremely poor at running complicated branched code (like A.I. code)

　　- Highly specialized approach, the cell is first and foremost an MULTIMEDIA processor that is best suited for HDTVs and a gaming consoles processor second. It offers extremes -- very good at running game engine, very poor at A.I. code.

　　GPU:

　　Today's top of the line 6800ultra has 16 pixel pipelines and 6 shader pipelines and is made up of 222 Million Transistors

　　X360 advantages and disadvantages

　　- ATI's next gen GPU (the R500) has a as unique architecture -- UNIFIED vertex/shader and pixel pipelines. It has 48 of these units that are automatically assigned a function

　　- Easier to program for but has a less higher theoretical peek than independet pipelines

　　- 10MB framebuffer that allows for "Free" anti-aliasing but limited resolution to 720P. For higher resolutions you "upsample"

　　- Unknown number of transistors (look for this number in the future)

　　PS3 GPU:

　　- officially stated to have 300 Million transistors with fixed pixel and vertex pipelines. Numbers not disclosed. If 6600GT is about 160 Million transistors, the 6800ultra 222 Million -- it is very likely that the PS3 GPU has 24 pixel pipelines and about 10-12 shader pipelines. I find it very easy to believe that the this GPU will be about twice as powerful as a 6800Ultra

　　- independent pipelines are faster BUT are harder to program for

　　Memory:

　　X360

　　512Mb of unified DDR3 memory with is shared by BOTH the GPU and CPU. Flexiablity is the obvious advantage. Disadvantage is that they have to be shared. Game developers can split the memory any way they like 50:50, 30:70 etc

　　PS3

　　256MB XRD for the cell

　　256MB DDR3 for the GPU

　　advantage is that the each has its own faster memory but each is limited to 256mb. While the CPU in the X360 can have a max of 512mb, the cell is stuck with 256mb.

　　Bandwidth:

　　X360

　　&#8226; 22.4 GB/s memory interface bus bandwidth

　　&#8226; 256 GB/s memory bandwidth to EDRAM

　　&#8226; 21.6 GB/s front-side bus

　　256GB/s from the 10mb frame buffer gives the X360 GPU a major advantage; it means the R500 isn’t limited by bandwidth and allows for free Antialiasing and a host of other effects. But the cost is that internal resolution is realistically limited to 720P. They may find a way around it. The original PS2 had on-die 4mb frame buffer. The game cube had off-die 2mb frame buffer.

　　PS3

　　Main RAM 25.6GB/s

　　VRAM 22.4GB/s

　　RSX 20GB/s (write) + 15GB/s (read)

　　SB< 2.5GB/s (write) + 2.5GB/s (read)

　　Pretty standard.

　　Video Output:

　　X360

　　Single DVI-output support sall HD resolutions (including 1080P and 1080i). Note that most games will probably be rendered at 720P but upsampled to 1080P like GT4 did with the PS2.

　　PS3

　　Dual HDMI (copy-protected DVI that combines audio) so that you can hook up two HDTVs. HDMI is a new format.

　　BUT for those of you who tried doing this on your computer, if a game runs @ 1080P single TV, you have to drop the resolution down on each TV to 720P so that you can have both.

　　The rest are extras

　　That only increase costs and don’t make gamming any better. PS3 has a lot of fat

　　Dual eithernet

　　Built-in wi-fi

　　Bluetooth

　　Multi-types of flash memory slots (SD, memory stick etc)

　　blueray

　　The above probably adds $100 extra to PS3

　　Conclusion

　　X360 and PS3 are about the same in power but approach it with different philosophy. X360 is less powerful BUT more flexible and easier to program for. PS3 is theoretically more powerful but less flexible and harder to program.