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#21

There are 3 main factors in how much RAM you can use:

  1. Motherboard. You just have to check the specs. They vary quite a bit.

  2. CPU. If you are buying desktop–as long as its fairly recent (within a year or two) should be ok. With Mobile CPUs, you will have to be careful about chipset.

  3. OS bitsize.

No matter who makes the OS, if it is 32-bit, the max RAM you can address is going to be 4 GB. It doesn’t matter if it is XP, Unix, Linux, or Vista. If you are running a 32 bit OS, you can’t address RAM beyond 4GB because the bits aren’t there.

This is not a bug, or a flaw. Its just the way the numbers work.

If you want more RAM, you will need a 64-bit OS, make sure you are using a 64 bit CPU, and check to make sure your mobo will support more. Non-server boards seem to capped at 8GB at the moment. I have seen server boards support up to 16, but not all will do that.

Even if you have more than 4GB and an OS/mobo/CPU combo that can use it–it doesn’t mean you get to use it. 64-bit OS’s are still…a bit fuzzy when dealing with 32-bit apps, which is the dominant target architecture right now.

Furthermore…if you go 64-bit, you will NEED more memory because your minimum ‘word’ size has doubled. So…you might not see the performance boost you are hoping for.

#22

A 32bit operating system can refer to 2^32 (some 4.2 billion) possible unique locations for each byte, hence the limit of 4GB.
This 4GB is in fact virtual memory. Each application has 4GB of virtual memry at its disposal. But those 4GB are equally divided: the Kernel gets 2GB (and these are shared between all apps) and the application itself also gets 2Gig.

When you install 3GB, there is still the upper memory limit that takes its (small) portion. You can still install DOS (or use it) on nowadays computers after all. Above the 3GB, things start changing drastically. For example your memory card’s memory takes up a chunk that is MUCH greater that what normally should be taken ( just look at your hex adresses). In fact, a 512GB vid card takes 512 GB from your RAM if you install 4GB.

In short: practically speaking, your application in 32bit gets maximum 2GB, but practically speaking, there are some overheads that reduce this to some 1,6GB.

With the actual prices of RAM , you can install 4GB, but your system won’t be able to use it fully, so there’s no real use for it as you won’t get a real advantage over the 3GB.
But no application in a 32bit system will ever get more than 2GB, unless you tweak the boot.ini. Which is not a good idea after all because, by giving 3 to your application, you take one from the kernel.

#23

That was a really good explanation Erik and Jhikar. Thankyou.

As far as ZBrush goes, do you have any specific recommendations? Should I save up and buy/build a machine with a quad cpu and 8G RAM?

I would be doing 3D ZBrush version of the sketch image attached. Probably very high polygon count. sketch.jpg

#24

8GB of RAM means 64bit. Ok if you also leave other apps running. For ZB 4GB would be enough.

here’s a useful thread:

http://www.zbrushcentral.com/zbc/showthread.php?t=49105

#25

There is a fuzzy bit you are kinda sidestepping: What you are referring to as virtual memory is more a virtual addressing. These addresses will map to either RAM or the swap file on a hard drive. Without tweaking your .ini your virtual address space per process is limited, but that isn’t the same as RAM utilization.

The more RAM you have, the more those addresses can map to RAM instead of HDD. RAM is MUCH faster than HDD access.

(Just wanted to clarify as the way you worded it suggested installed RAM was virtual.)

No matter how much RAM you have, Some portion of it will end up being used for those other tasks you mention–but the more RAM you have, the more remains for processes. The impact of having more RAM accesses instead of HDD accesses is non-trivial–and increases with the number of apps you have running at a time.

Also, I suspect concerns regarding Virtual Addressing can be sidestepped a bit by having modular processes that communicate with each other. Though, you may end up with a new set of headaches–but there is a potential for a kind of ‘soft-pipelining’ to exceed the limit in virtual address space…but I don’t know of anyone who is actually doing that.

But I think the theory is sound…

*Note: Anyone following along at home who wonders where to learn about this stuff, I recommend:

“Computer Organization and Design” 3rd edition by Patterson and Hennessy is highly recommended. And reasonably priced…for a Comp Sci text…

#26

Just for everyone’s information, from link to another thread in Erik post above, two systems people are happy using ZBrush with in 2007:

EVGA 680i mainboard
4GB Corsair dominator ram
E6300 cpu overclocked to 3.1ghz
Windows Vista Ultimate 64bit
8800 GTX

Vista Home Premium 64bit
EVGA 680i Motherboard
4gb RAM
qx6600 CPU
Nvidia 8800 GTS

I could probably get the stuff for these two systems (dated from 8/07) cheaper than the fastest/best of what is available now. But, now that it is 2008, any recommendations on a possible cost-effective improvement on the two above?

Oh, also… is premium RAM from the well-known companies (Corsair, Kingston etc) really better than run’o’the mill stuff from companies we’ve never heard of?

#27

Thanks Jhikar. You not only worded it very understandable, you also made things more clear for me.

I am not native English, so I sometimes “translate” literally from my native Flemish. Which cannot always be done.
I haven’t read that book, and I’m interested. What I know, I found on the internet, a bit here, and a bit there. And sometimes people come up with contradictions.

I also reread my first post, and I was more than unclear there: instead of XP, the operating system, I should have written: application.

shokan: I personally would go for the Q9450 instead of the Q6600 now. It’s the best value for your money. And, for ZBrush, the video card can be less, making it less expensive. Unless you want to game.
Even those better known companies have more and less expensive RAM. It’s speed, reliability,…
I personally would not take DDR3 for the moment. I would stick with DDR2 800.
I know Corsair and OCZ from experience and I never had a problem with them.

#28

Good news: eVGA makes great mobo’s.

Bad news: You may need a new power supply with them. They are cutting edge–so make sure your power supply has the right connectors. That particular one you will need a 24-pin plus another 8-pin. Earlier mobo’s only required an addition 4-pin connector.

This is not to be confused with the additional power requirements of the 8800…

Though…buying a new power supply for a new build is usually a good idea–and NOT one that comes with a case. They are pretty universally crap.

I recommend going with one that has modular cables–easier to work with and cleaner look when you finish.

With regard to memory–read up on latency and discriminate based on that–after size and format/speed.

Corsair tends to be pricy but decent. I’ve been happy with Geil lately. Cheaper but same performance.

OCZ is much like Corsair.

If you don’t want to do research on memory, and just want the cheapest, safest buy, Kingston Value Ram has earned a reputation for that. But in my experience–it is a little unstable. I’ve gotten read errors from it, but my not from my Geil or Corsair mem.

Not to be a shill–but Geil gives high mid-range features for slightly more than value ram solutions from Kingston, Corsair etc. I’ve been very pleased so far.

No matter who you go to for RAM–go to the mobo maker’s website and find the QVL for your mobo–and visit the RAM maker’s website and see if they recommend it for that mobo. If you can match RAM to mobo in this way–you will have much more peace of mind.