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Performance Question: Dual Processers or Dual Cores?

(21 posts)
  • Started 5 years ago by jd2066
  • Latest reply from jd2066
  • Topic Viewed 2216 times

jd2066
Posts: 3814

Hi,
I was wondering if anyone can tell me which is faster, two processors or one processor with two cores?
I thought it would the two processors but I searched with Google and found a result saying that it's the two cores so now I'm a bit confused.
I'm going to sleep now as it's nearly 2AM here so I'll have to check in the morning for replies.
Justin

Posted 5 years ago
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ScottW
Posts: 6609

Justin, let me start by saying that I am not a CPU designer, but I used to know some of them and I would ask them the same kinds of questions. Sadly the answer is still, "it depends".

Let's consider each core as a Processing Unit (PU). The 2 single-core processors have 2 PUs and the 1 dual-core processor has 2 PUs. It would seem to be even, but already there is a disparity. There is always a limit to the number of transistors that can be written on a single die for a single chip. When you increase the number of cores on a die, there is usually a trade-off of less compute power for each core. Using the same fabrication process, it's easier to put more on a single core processor -- more pipelines, more L2, more ALUs, etc. -- than on a dual core.

Now, let's imagine that all the PUs have the same compute power. The next disparity appears in the speed at which the two processors can communicate with each other to coordinate work. The 2 cores on the same die can be interconnected by a high-speed bus that is also on-die. This bus can easily be as wide as you please and will run at the core clock speed. The 2 separate processors, however, have to have an external interconnect bus which will always be slower, narrower, and more latent. As a result, for tasks that require coordination between PUs, the dual core has a huge advantage.

Now, let's get back to the real world. With 2 processors, each can be more powerful than the cores on a dual-core processor. As a result, any tasks that can be divided between the 2 processors which requires little or no coordination will be completed faster by the 2 processors. With tasks that make heavy use of the PU interconnect bus, the dual core has a big advantage and will be faster when the PUs are all of equal power and sometimes when they are not. This is why the answer is: "it depends".

Sometimes the CPU maker puts out single-core chips with a dual-core die in them and one of the cores is disabled. There is a situation where the single core variant has the same compute power as the dual-core version of the chip. However, it would be unlikely that someone would buy 2 of these single-core chips where the one core is disabled and run them in parallel. Much easier to get a single dual core.

Finally, the science of breaking compute work down into separate threads and how to dispatch threads in a multi-PU environment is still evolving. Does a deeper pipeline result in better real-world performance? Remember that Intel stopped using their Hyperthreading technology in the Core 2 design, but now it's back in Core i7. That just shows me that they are still learning and testing new ideas.

Posted 5 years ago
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jd2066
Posts: 3814

That makes sense. I was hoping for a simple yes/no answer but I know many hardware questions (Like AMD or Intel, ATI/NVidia, etc.) are in a "it depends" area and that is just the way it goes.
I was asking because I was thinking of upgrading the server I have for my home network to do file sharing, email, backup and other things to a more powerful one.
My current server has two processors, each with Hyper threading turned on so the Operating System sees 4 processors from that.
Here is what wikipedia says each processor is based on what cat /proc/cpuinfo told me:

Model                      | Frequency    | L2-Cache  | FSB      | Mult | Release Date
Intel "Irwindale" Xeon 2.8 | 2800 MHz	  | 2048 KiB  | 800 MT/s | 14x  | Sep 26, 2005

I was thinking I could get a single quad-core 3.0 Ghz processor (Along with the motherboard too of course) and it would be faster then two of those but then I wasn't sure.
I'm not sure if I even need more then 2.8 Ghz in speed though. The issue I'm finding is I want to use virtual machines but my current server doesn't support Intel VT and it only has 1GB of RAM.
Now that I think about it, all I really need is Intel VT and a bunch of RAM.

Posted 5 years ago
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ScottW
Posts: 6609

I looked up Irwindale and see that it is based on the P4 Prescott core. That's two technology generations back with the current tech being Core i7 and the previous being Core/Core 2. I certainly have little doubt that an i7 could run circles around those two Xeons.

When I think of a server for the typical home or SOHO user, I expect that most of them will be I/O bound. A file server, for example, is unlikely to be able to saturate a single i7 core with data from 1 RAID array being sent over 1 network adapter. A "server" processor, such as the Xeon series, would be recommended for a setup with multiple network adapters or LOTs of users requesting files at the same time.

Also you can't compare clock speeds between different technology generations because newer processors do more work in a single clock cycle.

Posted 5 years ago
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The Geek
Posts: 2059

You can get a fairly cheap Core 2 Quad these days, and drop as much memory as possible into the box. Virtual machines require enormous amounts of memory... the more the better. CPU isn't as important.

Hard drive speed is pretty important though... a slow hard drive will make a virtual machine pretty painful to use.

Posted 5 years ago
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jd2066
Posts: 3814

@ScottW:
True though I don't think I need a Core i7 processor. I think a Core 2 Quad would work.
And while you can't compare clock speeds only between generations you could compare it if you could compensate for how much you gain with a better chipset. Not exactly sure how I would do that though.

As for the difference between Core 2 and Xeon, I'm didn't really think about it when I first got a server. I just got one from Dell that looked like it would work and it did for a little while.
Now that I'm getting a new server, I'm attempting to find one that will do what I need without going overboard that should hopefully not need to be replaced within a couple years like my current server.

@The Geek:
I didn't even think of the hard drive speed but that makes sense.
Right now I run Gentoo Linux as the host OS and Windows Server 2003 as the guest OS. It works ok but it is slow to use and now I want to upgrade it to Windows Server 2008 which has higher requirements.
I use Gentoo Linux for the file/printer sharing, email storage, DHCP, DNS, Apache and other things that Linux does well. I use Windows Server for Active Directory, Group Policy, Windows Software Update Services (WSUS)Windows Deployment Services (WDS), Yahoo POPs, and other things that Windows Server does well.

Now, of course I don't really "need" any of those except for file/printer sharing but I'm a Geek and like to setup complex things just because :)

As for speed, how fast do you think would be enough? Like a 7200 RPM drive or would it be best to go to 10,000 RPM or higher?

@All:
I see now that I should have just named my topic "New Server Needed for Virtualization" or similar. It doesn't really matter now though.
Also would it be better to buy a computer or build one myself for a server? I have always thought I would rather buy a pre-built one just to save time and effort as I just want to poke around with the software not mess around with getting the hardware put together and working first. I can do so though if it's significantly cheaper or better that way.
Not to mention that I didn't want to do research for every little component like the motherboard, case, power supply, etc. When I just want to pick out a few things like hard drive, processor speed and amount of memory.
Thus why I have a Dell PowerEdge 1800 for a server, a Media Center computer from eBay and a Desktop computer from eBay.

The Media Center (Running Linux and mythtv) worked for a while as both a Frontend and a Backend but now I'm starting to run into problems as automatic transcoding of the PVR-500 MPEG2 stream/commercial flagging end up making the video playback have issues and the case doesn't have room for the amount of hard drives I have (In part to make room, the power supply sits outside of the case).
So my plan is to make my current server the mythtv backend and the current media center be a mythtv frontend for playback only.
My current media center has a Pentium 4 2.93GHz processor which should be sufficient when just doing MPEG-2/DVD/MPEG-4 playback. I'm not sure about HD Television but I don't need that at the current time.

Posted 5 years ago
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ScottW
Posts: 6609

Justin, you should get whatever processor you choose, of course. It just seems to me that the Core i7 is a good deal right now. The entry-level Core i7 920 is cheaper than the most expensive Core 2 Quad and performs better. From the tests that I have seen, it's performance is on par with the way more expensive Core 2 Extremes. Also, since the i7 motherboards use triple channel memory, you will have more slots to expand the RAM. The Asus P6T comes with 6 (!) memory slots. Of course, the motherboard will be more expensive but it will have more longevity.

As for the drive speed, at 10k or even 15k RPMs, a single drive will still leave your server I/O bound. Using multiple disks, perhaps in a RAID configuration, is better and still won't saturate the bandwidth of a SATA-II controller. However, the next bottleneck is likely to be your network. Even a gigabit ethernet network will be slower than what the SATA-II bus is capable of.

Posted 5 years ago
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raphoenix
Posts: 14920

jd2066,

You have so much going on, appears you are almost in a commercial venture. :) :)

I would probably start looking at Link below and then see what I could match up up on E-Bay.

http://www.intel.com/products/.....#38;s3=all

Think you are going to have to make a Build to get what you want at an affortable non-commercial price.

Best Regards,
Rick P.

Posted 5 years ago
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jd2066
Posts: 3814

@ScottW:
I did not realize that. I had assumed that the Core i7 would be far more expensive then the Core Duo/Xeon processors. It appears a quick check of Dell's site shows the Studio XPS system with a Core i7 processor is cheaper then a PowerEdge 1900 with a Core 2 Quad processor.
That seems a bit odd so I'll have to figure out why it's that way. Either way it seems the Core i7 processor isn't as much as I thought it would be.
For RAID, I'm not sure that I need that and there is one thing about RAID that has always bugged me: If I have a RAID system set up, my motherboard with it's RAID controller fails and I transfer that failed hard disk to another computer with a different RAID system, I wouldn't be able to read the data on the drive due to it having been formated in that one RAID system.
For the network bottleneck, I don't think I've hit that yet. In fact at last check I couldn't get full gigabit speeds. I just replaced my Cat 5E cables with Cat 6 cables so I'll have to test that soon and see if it helped.

@raphoenix:
I've stopped using eBay for various reasons and have switched to Newegg and Amazon for computer parts.
I'll look at prices on Newegg but it seems like the prices can't be much cheaper then buying a pre-built computer.
In addition to reasons listed in my last post, I have not built a computer from parts before, so I'm a bit worried I would mess something up and end up with an expensive set of non-working parts.
Though the processor and motherboard would be about the only new things to me as I have added/removed/replaced just about everything else inside various computers before.

Posted 5 years ago
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jd2066
Posts: 3814

Update on the RAID: The issue I listed probably only exists with RAID controller cards. I bet if I used the software RAID system in Linux I wouldn't have as big of a problem as it would be Linux compatible. Which is better then certain RAID card compatible.

Posted 5 years ago
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jd2066
Posts: 3814

I thought about it for a while and came up with the following configuration:
Usage: Due to the Core i7, it should be able to work as both a server and mythtv backend.
Processor: Core i7 Extreme
Memory: 12 GB ( 6 x 4GB )
Motherboard: Not sure yet.
Hard Drives:
1. 300GB hard drive with 3 partitions (Or somewhere around that size, depends on different things, will also be a fast drive for sure).
Partition 1 has a thin Virtual Machine host OS.
Partition 2 has Gentoo Linux.
Partition 3 has Windows Server 2008.
2. RAID 5 array for file serving and TV recording storage.
3 drives that are each 1 TB for available storage.
1 drive that is 1 TB for redundancy.

There are a few issues I still have to solve:
1. Figure out how to deal with current server.
Either get rid of it or just replace the components inside though that will be most of them so I still have to figure out what to do with those components.
2. Figure out what OS will work best as a VM host OS.
3. Make sure Linux RAID/LVM will work the way I want.
4. Find a Linux compatible voice modem to do things like automatic pausing of a playing recording when the phone rings and to function as an answering machine.

Posted 5 years ago
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jd2066
Posts: 3814

After looking into it, the Core i7 940 should work. I don't need to go to the extreme processor. In fact the Core i7 920 would probably be ok. I was worried about the going to 2.66 Ghz when my processor is 2.80Ghz but that small difference is probably made up by the improvements in the Core i7 design instead of the Pentium 4 design I have like ScottW said.

Posted 5 years ago
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jd2066
Posts: 3814

Well I looked on Newegg and found that I could get the componets cheaper by builting it myself instead of buying it so I just lined out a set of components and bought them.

Here they are:
Case plus power supply: COOLER MASTER Stacker 810 RC-810-KKA1-GP Black Aluminum Bezel, SECC Chassis ATX Full Tower Computer Case RS-850-EMBA 850W Power Supply
Motherboard: ASUS P6T6 WS Revolution LGA 1366 Intel X58 ATX Intel Motherboard - Retail
Video Card: EVGA 512-P3-N954-TR GeForce 9500 GT 512MB 128-bit GDDR2 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail
Processor: Core i7 920 Nehalem 2.66GHz LGA 1366 130W Quad-Core Processor Model BX80601920 - Retail
Memory: OCZ Platinum 12GB (6 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model OCZ3P1333LV12GS - Retail
Operating Systems hard drive: Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM SATA 3.0Gb/s Hard Drive (bare drive) - OEM
RAID Storage Drives (4 Drives): SAMSUNG Spinpoint F1 HD103UJ 1TB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM
Hard Drive SATA cables: None, I should have enough spare cables to cover those drives. I should probably double check though.

Hopefully, this works out, I'm still a bit worried about things not working as I've never built a PC before.
Though I should be able to do it as I know a lot about most of the components.

Posted 5 years ago
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raphoenix
Posts: 14920

jd2066,

A very, very wise choice to Build instead of purchase a pre-built machine. :) :)

Without the correct controlable hardware, your software and plans would have gone astray.

Best Regards,
Rick P. :) :)

Posted 5 years ago
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The Geek
Posts: 2059

That is going to be one incredible machine...

Posted 5 years ago
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jd2066
Posts: 3814

Just a quick update to say that I got the parts on Wednesday, me and my Dad put the computer together and it booted on the first try.
Now I just have a few things to decide:
* Which of the 100s of GNU/Linux distributions I want to use. I'm leaning towards Fedora Linux at the moment by Ubuntu, Red Hat, SUSE and others look good too.
* Do I even want to attempt a RAID 5 setup. I found some fairly scary articles online that said using 1TB drives with a RAID 5 is not reliable enough. One said to use RAID 6 and another argued that neither would be good enough to guard against hard drive failure. Sense I will have a 1TB drive outside of the RAID array to backup important data (like family pictures. Recorded TV shows don't need extra protection, it would be nice but they take so much space it's not really a practical thing to do so) so it shouldn't be that big of a deal if the RAID did fail (it would just stuck to wait to restore 1GB or so of data to the array if it totally failed).
* Other things I can't remember right now. I'll post them if I remember what they are and need help with them.

Posted 5 years ago
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raphoenix
Posts: 14920

Raid Wikipedia Information for those who are following this Build and Discussion.

http://en.wikipedia.org/wiki/R.....dent_disks

From an early Raid Controller Manual---

"The terms Fault Tolerance, Simultaneous Catastrophic Hard Drive Failure, Error Detection / Correction and Parity may appear foreboding but are based in mathematics and are relatively easy to quantify."

Regards,
Rick P.

Posted 5 years ago
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jd2066
Posts: 3814

For reference, here is the main link I saw: ZDnet Storage Blog: Why RAID 5 stops working in 2009
So far the fact that blog/news sites like zdnet always seem to always over hype issues that are really nothing to be concerned about makes me question how valid is it is in the first place but I should probably figure out if there is anything to it before doing the whole RAID thing.

Posted 5 years ago
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raphoenix
Posts: 14920

jd2066,

Suggest Running the Bios Locked Raid Array in 0+1 (10) (Striping / Mirror) (Performance + Redundancy) Configuration.

There are (6) combinations in which (2) HDs can experience Simultaneous Catastrophic Failure.

A Raid 0+1 (10) configuration provides Dual Fault Tolerance in (4) out of the (6) combinations.

You have NO control over HD Quality and Mean Time to Failure Rate. It is a statistical bell curve calculation for each HD manufactured.

Once you have the array with software up and running to your liking, suggest making a Ghost Archive or Similar Archive of the Array and storing it on the 1TB Backup HD.

Disconnect the 1TB HD from the system so it is just doesn't spin needlessly.

If one the HDs in the array fails, use another Exactly Identical HD to Replace the Faulty HD and Rebuild the Array.

If the array should experience Dual Simultaneous Catastrophic Failure, [rarely occurring (2) out of (6) possible combination], then Replace the (2) HDs which Failed and UN-Archive a Fresh, Up-to-date Array Configuration from the 1TB Back Up HD. (10 minutes time estimate)

The 1TB Backup Archive Should be Backed up on a 12 - 24 hour cycle based on the amount of data loss considered acceptable.

Suggest you use The Geeks Backup Time Schedule and Methods for Data Backup Archiving.

BTW: Besides SATA HDs, I use IDE HDs (also) to Backup Archives as they can be easily switched among different machines in case of MB Failure.

Please E-mail me if you don't understand this post because I'm not that good at explaining every small detail of how I setup my machines. :) :)

The proof is that my network has never been down for more than a few minutes as you have seen. That's why each machine has (6) HDs. (LOL)

Best Regards,
Rick P.

Posted 5 years ago
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jd2066
Posts: 3814

@raphoenix: That actually seems similar to what I was thinking of of doing.
It all made sense except for one thing, BTW: Besides SATA HDs, I use IDE HDs (also) to Backup Archives as they can be easily switched among different machines in case of MB Failure..
That doesn't really make sense for two reasons:
1. It seems you might be referring to the older Parallel ATA (PATA) standard by saying IDE but that is not what IDE actually means.
Here is a quote from wikipedia to explain it The terms "integrated drive electronics" (IDE), "enhanced IDE" and "EIDE" have come to be used interchangeably with ATA (now Parallel ATA). However the terms "IDE" and "EIDE" are at best imprecise. Every ATA drive is an "integrated drive electronics" drive, but not every "integrated drive electronics" drive is an ATA drive, as the term also correctly describes SCSI drives: They have the drive controllers on board and present the drive to the host as an array of blocks. -- Wikipedia: ATA - Current Terminology
I said might above as due to what it means I really no idea what you are referring to.
2. If you do mean PATA then that doesn't make sense as SATA drives are better then PATA drives in many ways.

I'll post more about my current configuration and possible RAID setup later.

Posted 5 years ago
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