Memory addressing: Macs vs. PCs

[Tony-S]

I'm not much of a computer guy, but I'm wondering if anyone in the know could comment on this article (http://www.appleinsider.com/articles/08/09/03/road_to_mac_os_x_snow_leopard_64_bits_santa_rosa_a nd_the_great_pc_swindle.html). It seems to suggest that Windows dramatically over reports available RAM and that Macs are able to address more RAM. Am I misreading it?

[doctorgonzo]

That's not exactly the case. The problem is that 32-bit operating systems, like the 32-bit versions of Windows, can only address a maximum of 4 GB of RAM. However, some of that 4 GB of RAM is memory-mapped to I/O devices, such as your video card. Thus, if you have 4 GB of RAM installed in a 32-bit version of Windows, and you also have a 512 MB video card, you will not be able to use all 4 GB of your system RAM. You will only be able to use about 3.2 GB of it. That's the way it works.

This is not an issue for 64-bit processors and operating systems, since they can address more than 4 GB of RAM.

The difference between Macs and Windows in the article is that in Macs, they apparently use some software tricks to move the memory-mapped areas above the 4 GB barrier even in a 32-bit operating system. So in a Mac, if you have 4 GB of memory and a 512 MB video card, you will be able to use all 4 GB of your system memory, as the video card addresses will be above that 4 GB address. I have never heard of this, but it sounds plausible.

In short, 32-bit operating systems are limited to 4 GB of memory or less. If you need more memory, you need a 64-bit architecture. That's why I use Windows XP 64-bit edition.

[Tony-S]

So if I understand you correctly, Win 32 will penalize you (in terms of available RAM) if you have a larger capacity vRAM card?

[tonylong]

So if I understand you correctly, Win 32 will penalize you (in terms of available RAM) if you have a larger capacity vRAM card?

It's more than Win 32 won't use the RAM. I have 4G of RAM with XP 32 and I don't get "penalized", it just doesn't all get utilized.

[Tony-S]

I must be misunderstanding that article. It seems to be saying that if you have a Win 32 system and you have 2.5 gb of RAM available with a 512 mb video card (with its own vRAM), then you swap in a 1 gb video card (with its own vRAM), then your available RAM drops to 2 gb, even though you still have 1 gb of physical RAM still available (that Windows cannot address??

[tim]

If you have 2.5GB of RAM then add a 1GB memory card I would expect it to use the 3-4GB range to address the video card, so you'd still have access to your 2.5G of memory.

[Moppie]

That whole article reads like typical mac fan boy windoz bashing.
It completely over looks the 64bit versions of Windows that have been around for several years now.

[Tony-S]

But is how I interpreted it correct? If so, then that is singly a compelling reason to NOT get a Win 32, right?

[tim]

But is how I interpreted it correct?

How you interpreted it may be correct, but your post above was incorrect.

[Moppie]

But is how I interpreted it correct? If so, then that is singly a compelling reason to NOT get a Win 32, right?


Not really, I think it has been badly worded.

The point to remember is the system is limited by how much ram it can USE.
My understanding is if you have 4GB in RAM and 1GB in vRAM, then the system can not use all 5GB at once, but it can use a combination of the 2 up to the 4GB limit.


There not yet many tasks performed on a PC (of any type) that absolutly must have more than 4GB of ram anyway. Video editing is about the only one I can think of where having access to lots and lots of RAM makes a large, and noticable improvement to performance.

Photo editing if your doing lots of ram intensive tasks, will benifit, but the performance increase from having more than 4GB of ram is not as big as having more than 1GB of ram.


As camera resolutions and file bit depth increases, file sizes will also increase, and in time having access to 8GB or more of RAM will make a difference, it might even be nessacary.

But, by then the latest windows and apple OS will be 64bit anyway, so no need to worry.


(one thing to note, if I owned a new 1DS MKIII I think I would want a 64bit OS now, as those RAW files, when converted to 16bit TIFF's, must be huge.
But, I have no problem batching processing hundreds of RAW and TIFF files from my 30D with 32bit Vista and 4GB of RAM.)

[PhotoJourno]

Well, I just took the time to read the 'Article'. Not even Woz would be able to explain the system comparison in such few words. And the diagrams, are as confusing as the actual subject is.

I run both a Mac and Vista with 64bit.

Mac OS does have the upper hand in RAM management, the mapping, addressing and freeing of space is done very seamlessly. Vista is quite sloppier, and reminds me to old software programming problems we would have, where data would leak onto RAM Addresses, and not dump correctly, meaning it continued using more and more RAM space, and in matter of a few mins to a couple of hours, the performance was severely degraded due to the overflow of useless data floating around.

While I have made it my rule never to agree with mods (just because everyone does, regardless of what), I am going to have to go with Moppie on this one. Windows OS running at 64bit on open architecture systems is being grossly misrepresented.

And on top of that, the MACies take a shot at Intel, who's now also supplying Apple with their CPUs and their supporting software.

[cosworth]

32 bit OS X cannot address more than 4gb. The software trick is that they do not measure the video RAM against the installed application (stick) RAM. Vista also does this. If you install 4GB of (stick) RAM it says you have 4GB of RAM. It does not report the video RAM - Just like 32 bit OS X....

Done.