iPhone Simulator = Intel
iPhone = ARM
区别很大,Intel目前的处理器主要为IA架构,IA-32即俗称x86,包括桌面处理器系列(赛扬,奔腾,酷睿等)以及服务器处理器志强(Xeon) 系列;IA-64是Intel独立开发得64位处理器,仅用于Itanium(安腾)以及后续产品Itanium 2,针对高端服务器市场。
ARM架构与IA架构本质上不同。在这里我们就简单比较一下IA32与ARM架构的不同。
IA-32处理器是基于CISC体系结构的,而ARM则是RISC的代表。RISC指令集与CISC指令集相比有以下特点:
1简单的指令集——RISC指令集只提供很有限的操作,基本上单周期执行每条指令,其指令长度也是固定的。
2Load-Store 结构——在RISC 中,CPU并不会对内存中的数据进行操作,所有的计算都要求在寄存器中完成。而寄存器和内存的通信则由单独的指令来完成。而在CSIC中,CPU是可以直接对内存进行操作的。
3更多的寄存器——和CISC 相比,基于RISC的处理器有更多的通用寄存器可以使用,且每个寄存器都可以进行数据存储或者寻址。
在应用方面,Intel的IA-32和IA-64架构处理器用于个人计算机和服务器,ARM处理器更多地用于嵌入式领域。
iphone vs gphone
Android 是运行Java的程式的。Java的程式是在JAVA的虚拟机内运行。所以Android 的模拟器是可运行的Android 的apk 文件;
iPhone的模拟器是运行x86机器代码,iPhone的真机是运行ARM的机器代码。ARM的机器代码的程式是不能在x86机器即iPhone的模拟器内运行的。
要有程式的源代码才可以在iPhone的模拟器编译x86机器代码及ARM的机器代码分别在iPhone的模拟器及iPhone的真机运行。
CISC vs RISC区别:
By Armin Gerritsen
- Which one is better? -
RISC vs CISC is a topic quite popular on the Net. Everytime Intel (CISC) or Apple (RISC) introduces a new CPU, the topic pops up again. But what are CISC and RISC exactly, and is one of them really better?
This article tries to explain in simple terms what RISC and CISC are and what the future might bring for the both of them. This article is by no means intended as an article pro-RISC or pro-CISC. You draw your own conclusions …
CISC
Pronounced sisk, and stands for Complex Instruction Set Computer. Most PC's use CPU based on this architecture. For instance Intel and AMD CPU's are based on CISC architectures.
Typically CISC chips have a large amount of different and complex instructions. The philosophy behind it is that hardware is always faster than software, therefore one should make a powerful instructionset, which provides programmers with assembly instructions to do a lot with short programs.
In common CISC chips are relatively slow (compared to RISC chips) per instruction, but use little (less than RISC) instructions.
RISC
Pronounced risk, and stands for Reduced Instruction Set Computer. RISC chips evolved around the mid-1980 as a reaction at CISC chips. The philosophy behind it is that almost no one uses complex assembly language instructions as used by CISC, and people mostly use compilers which never use complex instructions. Apple for instance uses RISC chips.
Therefore fewer, simpler and faster instructions would be better, than the large, complex and slower CISC instructions. However, more instructions are needed to accomplish a task.
An other advantage of RISC is that - in theory - because of the more simple instructions, RISC chips require fewer transistors, which makes them easier to design and cheaper to produce.
Finally, it's easier to write powerful optimised compilers, since fewer instructions exist.
RISC vs CISC
There is still considerable controversy among experts about which architecture is better. Some say that RISC is cheaper and faster and therefor the architecture of the future.
Others note that by making the hardware simpler, RISC puts a greater burden on the software. Software needs to become more complex. Software developers need to write more lines for the same tasks.
Therefore they argue that RISC is not the architecture of the future, since conventional CISC chips are becoming faster and cheaper anyway.
RISC has now existed more than 10 years and hasn't been able to kick CISC out of the market. If we forget about the embedded market and mainly look at the market for PC's, workstations and servers I guess a least 75% of the processors are based on the CISC architecture. Most of them the x86 standard (Intel, AMD, etc.), but even in the mainframe territory CISC is dominant via the IBM/390 chip. Looks like CISC is here to stay …
Is RISC than really not better? The answer isn't quite that simple. RISC and CISC architectures are becoming more and more alike. Many of today's RISC chips support just as many instructions as yesterday's CISC chips. The PowerPC 601, for example, supports more instructions than the Pentium. Yet the 601 is considered a RISC chip, while the Pentium is definitely CISC. Further more today's CISC chips use many techniques formerly associated with RISC chips.
So simply said: RISC and CISC are growing to each other.
x86
An important factor is also that the x86 standard, as used by for instance Intel and AMD, is based on CISC architecture. X86 is thé standard for home based PC's. Windows 95 and 98 won't run at any other platform. Therefore companies like AMD an Intel will not abandoning the x86 market just overnight even if RISC was more powerful.
Changing their chips in such a way that on the outside they stay compatible with the CISC x86 standard, but use a RISC architecture inside is difficult and gives all kinds of overhead which could undo all the possible gains. Nevertheless Intel and AMD are doing this more or less with their current CPU's. Most acceleration mechanisms available to RISC CPUs are now available to the x86 CPU's as well.
Since in the x86 the competition is killing, prices are low, even lower than for most RISC CPU's. Although RISC prices are dropping also a, for instance, SUN UltraSPARC is still more expensive than an equal performing PII workstation is.
Equal that is in terms of integer performance. In the floating point-area RISC still holds the crown. However CISC's 7th generation x86 chips like the K7 will catch up with that.
The one exception to this might be the Alpha EV-6. Those machines are overall about twice as fast as the fastest x86 CPU available. However this Alpha chip costs about €20000, not something you're willing to pay for a home PC.
Maybe interesting to mention is that it's no coincidence that AMD's K7 is developed in co-operation with Alpha and is for al large part based on the same Alpha EV-6 technology.
EPIC
The biggest threat for CISC and RISC might not be eachother, but a new technology called EPIC. EPIC stands for Explicitly Parallel Instruction Computing. Like the word parallel already says EPIC can do many instruction executions in parallel to one another.
EPIC is a created by Intel and is in a way a combination of both CISC and RISC. This will in theory allow the processing of Windows-based as well as UNIX-based applications by the same CPU.
It will not be until 2000 before we can see an EPIC chip. Intel is working on it under code-name Merced. Microsoft is already developing their Win64 standard for it. Like the name says, Merced will be a 64-bit chip.
If Intel's EPIC architecture is successful, it might be the biggest thread for RISC. All of the big CPU manufactures but Sun and Motorola are now selling x86-based products, and some are just waiting for Merced to come out (HP, SGI). Because of the x86 market it is not likely that CISC will die soon, but RISC may.
So the future might bring EPIC processors and more CISC processors, while the RISC processors are becoming extinct.
Conclusion
The difference between RISC and CISC chips is getting smaller and smaller. What counts is how fast a chip can execute the instructions it is given and how well it runs existing software. Today, both RISC and CISC manufacturers are doing everything to get an edge on the competition.
The future might not bring victory to one of them, but makes both extinct. EPIC might make first RISC obsolete and later CISC too.
Written by A.A.Gerritsen
for the CPU Site
March '99