What difference will the memrom chip

[Eidorian]

This has been answered sooooooo many times before....

https://forums.macrumors.com/threads/208508/
https://forums.macrumors.com/threads/207741/
https://forums.macrumors.com/threads/209507/
https://forums.macrumors.com/threads/207486/
https://forums.macrumors.com/threads/207938/

I've posted in 4 out of 5 of those threads.

 

[Core Trio]

Oh, and since Merom is 64-bit rather than 32 bit, you'll need what is essentially 2x more RAM than you would with the Yonah to get similar benefit. I have 1GB on my MacBook, but I'd expect to need 2 GB for a Merom notebook because the system uses 64 bits to store data rather than 32 bits. 512 MB of RAM will make the computer unusable, I'd think.

Also, I don't know how well 32-bit applications will run on a 64-bit system. With 64 bit software, 64-bit Mac OS X, and Merom, I'm sure things would be great, but I wonder whether there would be a bit of a performance hit because some 32-bit software will need to run in a 64-bit environment.

You blatantly made that up as you were writing it didnt you? I dont think you could be any further from reality on some points.

 

[daveL]

Here is a question to ponder: Since Yonah and Merom are pin compatible, if Apple just replaces the Yonah with the Merom, do you consider that a new revision?

Same goes for the X1600, will Apple just drop in a X18-1900 since they are also compatible?

Intel is also refreshing the Yonah chipset for Merom. The memory path performance is supposed to improve for the Merom chipset. As far as the integrated graphics improving, as mentioned in an earlier post, that's coming with the Santa Rosa chipset, which won't come to market until March of next year. Think rev. C.

 

[Abstract]

3. 32bit Applications will run at full speed comparable to the speeds of 32bit processors out there now.
4. 64bit capable applications will run faster than their 32bit counterparts because they are processed twice as fast (in theory).

Not entirely true either. Ok, I don't believe it's 100% accurate. 32-bit applications may not run at native speeds on 64-bit systems. So a 32-bit system will run 32-bit software faster than a 64-bit system running 32-bit software.

Ok, forget this. I checked Wikipedia and searched "64-bit"

Wikipedia:

While 64-bit architectures indisputably make working with huge data sets in applications such as digital video, scientific computing, and large databases easier, there has been considerable debate as to whether they or their 32-bit compatibility modes will be faster than comparably-priced 32-bit systems for other tasks.

and

Theoretically, some programs could well be slower in 64-bit mode. Under some architectures, instructions for 64-bit computing take up more storage space than the earlier 32-bit ones, so it is possible that some 32-bit programs will fit into the CPU's high-speed cache while equivalent 64-bit programs will not. In basic terms moving 64 bits at a time to perform otherwise 32 bit work simply requires more processing effort to/from memory. A common argument is that, in applications like scientific computing, the data being processed often fits naturally in 64-bit chunks corresponding to double-precision floating-point types, and will be faster on a 64-bit architecture because the CPU will be designed to process such information directly rather than requiring the program to perform multiple steps — this is erroneous, however, because most 32-bit CPUs already have a 64-bit wide data bus and 64-bit registers for floating-point quantities. The only speed advantages come for manipulating 64-bit integer quantities, but this is rarely a performance-limiting task even for applications (such as large-file I/O) that require such manipulations.

I don't know. I just don't think people will see speed benefits by going 64-bit right now until everything is released as 64-bit.


I wonder if Intel did this for Merom as well.....

Other software must also be ported to use the new capabilities; older software is usually supported through either a hardware compatibility mode (in which the new processors support an older 32-bit instruction set as well as the new modes), through software emulation, or by the actual implementation of a 32-bit processor core within the 64-bit processor die (as with the Itanium processors from Intel, which include an x86 processor core to run 32-bit x86 applications).

 

[darkcurse]

Well, if we were talking about ground-up 64bit based processors(e.g. Intel's Itanium which uses the IA-64 instruction set) then I guess you would be right. But the instruction set being used now in AMD and Intel systems would be the x86-64/EM64T. In that sense its different because it is a predominantly 32-bit processor which "supports 64-bit general purpose registers, 64-bit integer arithmetic and logical operations, and 64-bit virtual addresses" (Wikipedia)

Operating mode explanation

There are two primary modes of operation for this architecture:

Long Mode
The intended primary mode of operation of the architecture; it is a combination of the processor's native 64-bit mode and a 32-bit/16-bit compatibility mode. It is used by 64-bit operating systems. Under a 64-bit operating system, 64-bit, 32-bit and 16-bit (or 80286) protected mode applications may be supported.

Since the basic instruction set is the same, there is no major performance penalty for executing x86 code. This is unlike Intel's IA-64, where differences in the underlying ISA means that running 32-bit code is like using an entirely different processor. However, on AMD64, 32 bit x86 applications may still benefit from a 64-bit recompile, due to the additional registers in 64-bit code, which a high-level compiler can use for optimization.

Legacy Mode
The mode used by 16-bit (protected mode or real mode) and 32-bit operating systems. In this mode, the processor acts just like an x86 processor, and only 16-bit or 32-bit code can be executed. 64-bit programs will not run.

The whole wiki entry may be found here

So, entry no.3 still stands I guess, since benchmarks conducted using a 32-bit OS running 32-bit programs yield performance that is comparable or in some cases faster than non x86-64 processors on a clock-by-clock basis.

Of course, if we were using a fully 64-bit OS then the situation might be different. But since a major portion of OSX is still only 32-bit so any increase in performance from Merom would be because of things like increased FSB, memory speeds and general chip architecture enhancements/tweaks not because of 64-bit support.