DDR Ram question - dual athlon physics computer

[lollipopgrrrl]

Hello all :)

What a fantastic site ! (pcguide) What lovely forums!

To briefly introduce myself, I am a physics student from Melbourne Australia. I have just commenced a PhD, and my supervisor is buying me a new computer (hehe it's very exciting actually ).

I have done some research and decided on a dual-athlonMP system. My supervisor uses a data analysis and visualisation package called IDL (Interactive Data Language, a little like mathematica or something like that) which is multi-processor aware, and we will probably also use Fortran90, which is smp aware.

I am not yet sure what kinds of calculations we will be doing with it, but they will probably involve analysing image data taken from an electron microscope(TEM Lorentz microcraph), and also solving various partial differential equations.

Although my supervisor is getting by just fine at the moment on an older slower system, I figured that I might as well look at getting the most power we can reasonably expect with our budget of around 3500AUD (approx 2200USD, inluding monitor), especially since we can't be sure yet what it will be used for and it needs to still be viable in 3 years or so (length of an Australian pHd approx 3-4 years)


Anyway, to get to my question! I have put in an order at a reputable supplier (since it's for work we need extended warranty etc) for a dual athlonMP 2400 system with the following basic skeleton:


----------------------------------------------------
Motherboard: Iwill MPX2 AMD 760MPX, IPS, 4 DDR DIMM, Iwill Processor Shelter (IPS), ATA/100, AGP PRO

Memory: Kingston 512MB 266MHz DDR PC-2100 ECC Registered DIMM CL2.5

Hard Drives: 2*Western Digital 40JB 7,200rpm Ultra ATA/100 8.9ms 8MB
Ultra ATA/100 IDE interface, 8MB Cache, 8.9ms avg seek time, 10.9ms avg write seek time.

Video Card: 64MB Radeon 7000 VE

Chassis: Coolermaster ATC-710 GX1, 4x5.25", 6x3.5", Black
------------------------------------------------------


I am concerned though that this is not going to be enough RAM for such a system. It is the amount that the supplier was selling standard with their "workstation" AMD model, of which my requested system is a variant, and it sounded like "stacks" to me at the time when I ordered since I currently have 128mb, only upgraded from 64 about a year ago :)

However a couple of people who saw the quote expressed some concern, and after reading some more about memory bandwidth and so on (and becoming thoroughly bewildered!), I decided I definitely should think about whether to get more RAM.

They have not started putting the system together yet, and presumably even once they have, a RAM upgrade should be reasonably straightforward since it is the kind of thing they do all the time. So it may still be possible to change the order at this stage. If not, I am fairly confident I could upgrade the RAM myself at a later date, although I'm not sure how this goes with the warranty etc.

So finally my specific questions!!!

1. Do i need to upgrade right away, ie is that just far too little RAM for such a system, or is it ok 'to begin with' and then I could upgrade in 6 months or a year?

2. if I *am* getting more RAM, would it be better to change the single 512mb DIMM for a single 1024mb DIMM, or to get 2 512 mb DIMMs?

3. Would it be possible to have one 512mb and one 1024mb DIMM in such a system?

4. How do DDR RAM and the "point to point" bus of the dual athlon setup interrelate?

5. Should I be loking at PC2700 RAM instead of PC2100?

The reason I ask is that I have been reading the thread in this forum about a new gaming computer for Lisubie[excerpted below], and I noticed that it might be better to have two DIMMs to take advantage of DDR support (which my motherboard will have I believe).

Now a 2400+ Athlon processor is , in my naive understanding, capable of processing data at a rate of around 2Gb per second or a bit more. One guy I spoke to said you should have "at least a GB of RAM per processor" for this system. This would be blowing our budget a little, but worth it of course if it really is necessary to access the full potential of the system, seeing as we are already spending a fair bit.


Here are some excerpts from the thread that got me thinking about all this - apologies if I have wrongly attributed any of these quotes, it gets very confusing with all the nested replies and so on!

I intend to read this thread a bit more thoroughly and to browse the rest of the forums/pcguide site as soon as I get a chance ( I have only skimmed so far), but any advice/explanations/clues/tidbits at this stage are highly welcome!

Thank you,

Wendy Langer :)

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Thread:

The PC Guide Discussion Forums > General Discussion > Buying and Upgrading Advice > a gamer's computer to last minimum two years


03-23-2003 09:37 PM

Lisubie
Geek Disciple

Registered: Mar 2003
Location: In the town which is home to „die Martinskirche", built in 911, for a bunch of monks.
Posts: 36
a gamer's computer to last minimum two years
Hi, everyone. Very nice place here!

I want to build our computer for the first time - our previous two were systems- bought here in Germany so I won't bother to list makers.

This computer should play the newest games (e.g. Freelancer, Unreal 2, Splinter Cell and their coming associates) for at least two years (in ever decreasing resolutions, I know). I want stability, know nothing about overclocking and such, and do not expect to stick in more than 1 new CPU or game card in the next two years.



BigBlue66
---------

I'm running two sticks of 256mb each so I can make use of the dual channel DDR support.



Lisubie
-------
interesting. Right, one can slow the FSB to match the processor, and you personally report better performance. Sounds good. Thank you. Oh dear, "dual channel DDR support" Now, does this mean two sticks are better than one, as in you can read or write simultaneously to both more so than simply within a 512MB stick?


Saphalline
----------
Dual channel DDR is a really cool "bootstrap" technology. And yes, it works just like you described it - being able to access two sticks of RAM simultaneously, which results in twice the RAM performance (theoretically). In this case, get a motherboard based on the NForce2 chipset from NVidia. Works wonders for the Athlon platform, but it works even better for the P4 platform ('cause the P4's bus bandwidth is normally starving with single channel DDR).


Saphalline
----------

P4 FSB is 64-bits wide * 133MHz bus speed * quad-pumped bus (533MHz total) = 34112000000 b/s = 4264000000 B/s = approx 4 GB/s

DDR333/PC2700 RAM is also 64-bits wide * 166MHz bus speed * double date rate (333MHz total) = 21312000000 b/s = 2664000000 B/s = approx 2.5 GB/s

Standards for bandwidth generally lean towards the 1GB/s = 1 billion B/s, which is where you get the usual results of 4.2 GB/s for the P4 bus and 2.7 GB/s for PC2700 RAM (thus the number "2700" in the name). But when I calculate bandwidth, I use the binary system just like my puter does when it runs these bandwidths, so the above numbers are binary based.

[Budfred]

Welcome to http://www.pcguide.com/ubb/pcgubb.gif

I can't answer most of your questions, but I can tell you that the amount of RAM you are likely to use depends a lot on your OS. If you are using Win2000Pro or WinXP, at least a gig of RAM for your system would probably be the way to go and you could go to 2 gigs if you want. You seem to have 4 slots for RAM so I would go with 512 meg... They are cheap right now (relatively speaking) and you are unlikely to ever need 4 gigs with this system. In a few years that may change, but for now you are at about the limit. Others can tell you more...

Another thing I would wonder about given the work you are doing. I would wonder if a single 64 bit CPU might be better than 2 32 bit CPUs... The 64 bit CPUs from AMD have just been released so they are expensive, but may be worth it to last for as long as you want....

[Rick]

I use a dual system for Cad a Graphics work. (Amd-1800MP)

I started out with only 512 meg of ram. And Soon installed another 512 ( 1024 total)

Under WinXP Pro after boot up I have 120 meg of ram in use ( total of 25 process’s running)
I have yet to find anything that will cause a LOW Memory warning


Depending on your software and the amount of data
You should be safe to start out at 512 or 1024 ( I’d go the 2x512 = 1024)
IF You need more you can always install it later ( another 1024)
You would need to check the Mother board spec’s for the best memory configuration
having 512 installed and later adding another 1024 stick should work ..
However you may find it less expensive to install 2x512 or 4x512
However doing so may create a heat problem ( Hot spot) in the case

[Rick]

Originally posted by Budfred
Welcome to http://www.pcguide.com/ubb/pcgubb.gif

Another thing I would wonder about given the work you are doing. I would wonder if a single 64 bit CPU might be better than 2 32 bit CPUs... The 64 bit CPUs from AMD have just been released so they are expensive, but may be worth it to last for as long as you want....

I’d wait on the 64 bit

I’m not entirely sure that his software even being dual /smp aware would take full advantage of the 64 bit

Kind of like Win Explorer running on this dually
Doesn’t even move the cpu usage meter

[lollipopgrrrl]

**********************

Thanks Budfred & Rick :) :)

I am planning to use Windows2000 pro and linux - probably Debian linux.

I'm a she not a he! ;)

It is reassuring to hear that a need for 4GBs is unlikely, as buying another 1.5 Gbs at this point would be pretty expensive...buying a further 512 is more likely though...and then perhaps upgrading further to a total of 2Gb later on would be the best option. It seems from the maual that the motherboard can use various combinations of sizes of modules, as long as thety are all at the same speed. Also, I think it will only take pc2100 RAM not 2700(I have quoted tha manual down the bottom of this post if anyone is interested :)

If it creates a heat problem, what can be done - is there more likely to be one if the DIMMS are different, or does it depend on the make of the RAM, or something else entirely? (Can you get 'RAM fans' ?!)

64 bit - yes a 64 bit processor would probably be fantastic!

In the benchmarks of the IDL data language I mentioned, which ranks 179 systems running the suite (submitted by users), the top two places were both taken by 64 bit machines!


1. Compaq/Digital XP1000 EV6 (21264A) 667MHz 2048MB

2. Compaq XP 1000, Alpha EV67 667MHz 1278MB Tru64 UNIX 4.0F

(http://astrosun.tn.cornell.edu/idlspec/is2.html)


And then 3rd to 6th places are various pentiums, and the first dual athlon machine comes in at 7th place. I was a bit worried when I saw this, since if a single pentium is going to outperform a dual machine anyway, and be cheaper, then it would have been a better option. However, these benchmarks are quite old now, and were discontinued in Feb 2002, basically because the benchmarking tool was too weak and was unable to stress modern systems! More importantly, I *think* that these benchmarks test a number of features of iDL, with the array manipulation functions, (which would be the most sped-up by having two processors, being only one facet.)

I wrote to the guy who maintains the benchmark site, and he wrote back the following:

"I'm running IDL on dual-processor AMD. You need at least 100,000
element arrays to get threading to be efficient, but it usually scales
well then:

http://groups.google.com/groups?selm=pan.2002.11.15.22.20.07.884052.11003%4 0as.arizona.edu

However, for pumping through the (slow) IDL interpreter loop, a faster
FSB would probably help (as it would for most memory operations, which
IDL is notoriously heavy on), not to mention the increased clock speed.

> An Intel-based dual-xeon system is probably a little outside our price
> range, however an AMD-based dual athlon-MP 2000+ system looks to be priced
> just about right.
>

I have a dual AMD 1600MP and it goes along rather nicely.


> The other option would be to go with a *single* processor Intel based
> system, something like a pentium4 2.4 Ghz should be just possible within our
> price bracket. :)

If you are dealing with lots of operations on large images/vectors, go
for the dual, otherwise you'll feel the speed difference of a single
processor more. If you will be calling out to FORTRAN from IDL, or
running concurrently, a dual will also help there, although the FORTRAN
code itself, unless you go to some trouble to make it so, won't be
threaded (i.e. will probably run somewhat faster on the Pentium 4)."
************************************************** *******************





The thing is, I am not sure yet what we will be doing. However my supervisor said he is currently dealing with 300*300=90 000 element arrays, so we could easily go over the 100, 000 limit where the dual processing really "kicks in". Also, I will be using Fortan90, which is written to be parallelised easily (apparently, not that I have ever done it!) Finally, I guessed that it might be good to learn a little about parallel programming, since multi-processor systems will become more and more common.

But the same argument could be applied to 64 bit. I had a look at opterons after your suggestion, but there is a lot to learn...I don't really understand about OS/application support. It is great that the opteron supports both 32 and 64bir 'natively' as it will encourage the adoption of 64bit more widely, howeveer at this point in time, what OSs and applications will actually support it? if my application doesn't use it, it will obviously still run in 32 bit mode, but then there is no point having the 64bits? If an application supports 64bit unixes(which iDL does), will this mean it will be more likely to be ported to the opteron architecture quickly? Would it already *be* supported for the opteron under a 64 bit linux?



heheh I am getting more and more confused. I read a quote somewhere once that said "We start out confused and end up confused at a higher level", which I think is a pretty good description of my mental state!

Thing is, I have already put in the order for the dual athlon system. The company I have ordered from (www.emagen.com.au) has just announced they are launch partners for the opteron, so I will ask them about it when I call them next week :)

Odds are my supervisor will want to upgrade himself within the next couple of years, so perhaps the opteron would be a good option at that point...


-------------------------------------------------------
Excerpt from Iwill mpx2 motherboard manual:
------------------------------------------------------
Memory Specifications
--------------------

The motherboard has four DIMM module sockets. This motherboard uses DDR SDRAM DIMM modules for system memory. The system memory specifications are:

PC1600 or PC2100 DDR SDRAM DIMM modules.

Uses 64mb, 128mb, 256mb, 512mb or 1Gb DIMMs.

Maximum 2Gb unbuffered and 3.5 registered total system memory.

Memory Configuration Options:

This motherboard has flexible memory configuration options. Please note the following:

Supports any mix of 64mb, 128mb,256mb, 512mb or 1Gb modules.

Any capacity DIMM may be used in any socket as long as the total memory limit is not exceeded.

Modules should be the same speed for best system performance.

Both unbufered and registered DDR SDRAM are supported.

Do not mix unbuffered and registered memory.

Unbuffered Memory: If you install unbuffered memory, the chipset supports up to 2Gb total system memory only installed in the DIMM1 & DIMM2 sockets.

Registered Memory: If you install registered DDR memory, the chipset supports up to 3.5Gb total system memory. if you install four 1Gb modules, the system will only recognise 3.5Gb
-----------------------------------------------------

[Budfred]

My thought with the 64 bit CPU is to provide a buffer for the future, but it will take at least a year of two for software applications to make optimal use of it.... If your supervisor upgrades in a year or two, the technology may be ripe at that point...

[lollipopgrrrl]

Yep, the future-buffer issue is pretty tricky :)

Thinking about it, it probably only needs to be ok for the next 2 years, as then we could pass it on to a newer student, and I can upgrade at that point - they can have it for a year, and then it can end up in the undergraduate labs or something.

I've changed my sig as it was ridiculously long :) I liked it (the sock-cryptography one) and it is ok on emails, but in a forum such as this it just gets in the way between the posts!

Wendy :)

[Budfred]

Actually, I never really read the thing about the sock, I thought it was part of what you were quoting and couldn't figure out what it had to do with anything.... It certainly was longggggg:D

[saphalline]

Ooh, I read this thread earlier, but that's all the time I had! :eek: Finally getting to put some input into it now (hehe, couldn't resist that pun).

Ok, first off, the overall specs on that machine are indeed impressive. Dual-CPU configs are always facinating but most of us never need that kind of power! :p Nice to get into it, tho. Here's my answers to your specific questions from your first post.

1. Considering your budget, that amount of RAM is perfectly OK for now. One note, however, is to ask the company selling you this computer is to ask if it's OK for you to upgrade simple things like the RAM (ie, no voiding of warranty). The reason for this is because RAM is dirt-cheap and darn easy to install (you don't want to be paying labor fees for something as simple as RAM installment!).

2. Looking ahead in terms of RAM upgrades for that config, I see starting out with a single 512MB stick of ECC registered RAM (max 3.5GB), then installing 3 x 1024MB sticks as you (or the next user) upgrades so that you eventually end up with 3.5GB of RAM using all 4 RAM slots. :D Works out perfectly!

3. DDR RAM works in single sticks, no pairs are required. You can have different amounts of RAM in each slot without having any problems. No worries there.

4. Any dual-CPU chipset tries its best to make sure that both CPU's have access to RAM whenever they want. The problem is that there's enough RAM bandwidth for one CPU, not two - so you do get a performance hit there, but you'd get that no matter which SMP workstation system you're using.

On a side note, the new 64-bit CPU's from AMD also have a chipset that allows each CPU to have its own RAM, which boosts performance but requires (naturally) that you buy RAM for each CPU. Double costs there, but more efficient. I'll talk about the 64-bitters later here...

5. No, if your system vendor is giving you PC2100, just go with it. Although the difference in price between the two is almost nothing, it's a different story with ECC registered RAM. Registered RAM is designed for the ultimate in data integrity, which is pretty much the only type of RAM you should be using if you need a dual-CPU system. The problem is that it takes longer for RAM manufacturers to produce this higher quality stuff so there's still a price premium for ECC registered PC2700 RAM vs PC2100. Short answer - stick with PC2100 since your system will never use the extra speed of PC2700, and when you buy RAM upgrades, you must use the same type! ECC registered.

Specifics about your system: I like the case! That's a high quality case right there! Excellent design and cooling. The video card, however, leaves much to be desired - depending on what you're gonna be doing in terms of graphics. Tell us more about the graphics end of your programs/activities and we can help you further with that. It just seems a little light-weight for a dual-CPU system, but if you're not even gonna touch a CAD program, then it's fine. (displaying array elements doesn't require much graphical power! :p )

In terms of going with two AthlonMP's vs a single P4, yeah right! A P4 will never even approach the amount of power that two AthlonMP's can dish out! Whether or not you'll use that power to justify the cost, well, I think a Physics student is more than capable of doing that, especially given your time frame of 2-3 years!

What else?... Oh yeah, the heat issue that was brought up. With that case, I don't think heat will be a problem. RAM gets a bit warm, yes, but unless you overclock it (make it run faster than it was designed to) then it will operate just fine. Same with everything else, but again, ask the vendor about system/case fans. You'll want all the fans in! Just to be safe. I believe that case takes four 80mm fans. The two in front blow over the hard drive cages! That's a good thing. ;)

Finally, my take on the 64-bit CPU's. Yeah, they're gonna be great. More CPU power for less! :D For your situation, tho, you'd need a dual-64-bit CPU system, which isn't likely to be sold for cheap anytime soon! As for Budfred's idea of a single 64-bit CPU... nope. Not gonna work. Even though the math adds up ;) the processing doesn't. You're running 32-bit software, and while a 64-bit CPU is backwards compatible with 32-bit software, it does so by acting like a 32-bit CPU. It can't process two 32-bit threads at once, hence you'd still need a dual-CPU system. Maybe in a year or two, dual-64-bit CPU systems will make sense, but right now they're simply not available and untested (for hardware compatibility and such).

I think that's about all I can say right now...

[Budfred]

In a year or two there will be 64 bit software available which is likely to make the need for the dual processor moot. On the other hand a dual processor with 64 bit processors and software would probably be about what supercomputers were a few years ago....

[saphalline]

In a year or two there will be 64 bit software available which is likely to make the need for the dual processor moot.That's true. I see what you were getting at there. And a dual-CPU system with the Hammer series would be nearly unstoppable! :eek:

AMD processors always please with high IPC counts and efficient core architectures. Moving up to 64-bit with that built-in memory controller can only improve things! Let's see if the multi-CPU system finally makes a break for the home enthusiast...