Performance Discussion - The Biggest Bottleneck

[Arcadian]

I wanted to spawn a discussion on system performance. More specifically, what do you think is the biggest bottleneck in a computer system?

These days, we are starting to see diminishing returns for improvements in various hardware. It has gotten to the point where insignificant improvements are taken to be huge leaps in technology. We used to live in a time where the newest video card gave a 20-40% improvement over the competition, whereas today it is more like 5%. CPUs used to give similar increases, and now they, too, are giving < 5% improvements.

So what is the bottleneck? What is preventing our systems from doubling in performance? Is it system memory? Is it the CPU or the video? Is it AGP? Or front side bus speed? Is it the hard disk or removable media? Or is it something else entirely?

Before I give my opinion, I was just curious on what other people thought. So come on... state your opinions. Keep it technical, if you can, and site examples if possible. Web links are really great, too.

[nkeezer]

As for what's holding up performance on the most general level, I think the answer to that is easy: hard drives. Everything else in a computer is measured on the order of nanoseconds, yet hard drives are still way up in the millisecond range. As long as things like seek times stay up at say 9ms, things won't change much. I mean, the processors will get faster and the computer will be able to crunch more numbers, but in overall use, it won't "seem" that much faster. Unfortunately, I'd consider this to be a limitation of hard drives themselves, i.e. until we get away from mechanical forms of storage, and into the realm of say holographic or other optical storage methods, then things won't get dramatically better.

And the comments about smaller performance increases with succeeding generations of technology...I think that's only partway true. If you look at CPU speeds over the past couple years, processing power has actually beaten the estimate from Moore's Law (due to the chip wars between Intel and AMD). So in that sense, performance is still increasing just as much as before. However, I think the greater scale leads to the impression of diminishing returns. For instance: around 1995, Intel had the 100MHz Pentium. They followed up with chips running at 120MHz and 133MHz, representing increases of 20 and 33%. Pretty hefty. But the numbers themselves are small in comparison to today's chips...it'd be akin to Intel releasing a chip running at 800, then following it with a chip running at 960 (20%) and 1066 (33%). Which of course we know they don't do. In other words, the increments between chips has stayed pretty much the same, but the frequency of their releases has been increased instead (hell, I remember a few years back, it seemed like it took 3 or 4 months for a new chip to be released).

And then of course there's the bigger question: is the extra speed really necessary? For the most part, I'm inclined to think that it isn't. I upgraded my PII 350 to a Celeron II @877 several months ago. To be honest, the differences between the two processors in typical everyday use was negligable at best. To satisfy my own personal curiosity, I even timed how long it took to do certain things on my computer with the two different chips (the results are actually online: http://jpnsystems.8m.com/celeron566/index.html) but it turned out that the new chip didn't make much of a difference at all. And the 250% boost in clock speed only really came into play with things like video compression, where the extra clock cycles can be put to use. The rest of the time, the chip sat on it's *** waiting for the hard drive to catch up.

I'm not sure what the point of all that was

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www.nweb-design.com <-- Send me a client, I'll send you a 5% finder's fee

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[zombor]

Originally posted by nkeezer:
As for what's holding up performance on the most general level, I think the answer to that is easy: hard drives. Everything else in a computer is measured on the order of nanoseconds, yet hard drives are still way up in the millisecond range. As long as things like seek times stay up at say 9ms, things won't change much. I mean, the processors will get faster and the computer will be able to crunch more numbers, but in overall use, it won't "seem" that much faster. Unfortunately, I'd consider this to be a limitation of hard drives themselves, i.e. until we get away from mechanical forms of storage, and into the realm of say holographic or other optical storage methods, then things won't get dramatically better.

But hard drives have always been measured in ms and memory has always been measured in nanoseconds...that hasnt changed, they've just gotten smaller(proportionally?). I think its due to the FSB. Think about it, when we had 133mhz pentiums, wasnt the bus speed 66? Im not sure, because the first computer i built was a 233 k6, then before that, i just owned a 486. But a 66 bus speed compared to 133 or 233 is a bigger memory speed to cpu speed ratio than, say 133mhz buss to 1133mhz cpu speed. The problem with just speeding up the bus is the heat issue. Im assuming the chipset would generate gobs and gobs of heat running at 1133Mhz! But if memory/bus/cpu speeds were equal, the proc wouldt have to go into "wait states(??)" waiting for the memory to catch up to itself.

This is all based off of some articles i was reading a year or so back, so it may not all be 100% accurate. Im open to criticizim to it because it is probably partly wrong.


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Compaq Armada E500
650MHz PIII 128MB RAM
8MB ATI rage mobility
11GB hard drive/DVD
dual booting win98/2k

who said you cant game on a notebook????

[nkeezer]

My point exactly: hard drives as so slow compared to the *other* components in a computer, that huge increases in processing power and the like are effectively covered up (in normal use) by the lagging hard drives. So until we can get rid of spinning platters and other mechanical components as a means of data storage, then hard drives will continue to be the biggest bottleneck.

Originally posted by zombor:
But hard drives have always been measured in ms and memory has always been measured in nanoseconds...that hasnt changed

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www.nweb-design.com <-- Send me a client, I'll send you a 5% finder's fee

"You have just destroyed one model XQJ-37 nuclear powered pansexual roto-plooker....and you're gonna have to pay for it." -- Frank Zappa

[zombor]

but the hard drive isn't continously being accessed like memory is. it is for loading things like games and programs, then once theyre loaded, it never accesses the HDD for that app again to load it anyway. In game performance has nothing to do with HDD speed(unless your using virtual memory!). although speeded up HDD will increase overall speed, its not really the "limiting reactant" as my chem teacher said today

And windows would load 10x faster if all the legacy code for the architecture was destroyed, but thats a whole other topic!

------------------
Compaq Armada E500
650MHz PIII 128MB RAM
8MB ATI rage mobility
11GB hard drive/DVD
dual booting win98/2k

who said you cant game on a notebook????

[Ymaster]

Limiting factors...Slow refresh rates for monitors at 1600X+ Just wasted FPS...

Parts that work non-asink.

There are current techs on faster hardrives with no moving parts. They use crytal and can store the internet.. heh...joke

If HD's where as fast as dram. Then there would be no point in dram.

I personally think the limiting factors are the Motherboard to hardware parts interfaces..Pci, ISA, AGP...If we had agp slots for all cards...Call it apci?

When the speed of Cpu's have reached there max we will just make duel cpus a standurd. Multi CPu's are what made the super computers that tolk up rooms into those small Doctor Who sized Tartuses..

I dont want the see video cards anymore. I want to see GPU sockets! Adding Alphas to are Video GPU's like we do to new cpu's...Gives a whole new light to onboard video?

[Ymaster]

I dont want the see video cards anymore. I want to see GPU sockets! Adding Alphas to are Video GPU's like we do to new cpu's...Gives a whole new light to onboard video?

[/B][/QUOTE]

Now that I think about it..Why not add on-die cash to the Gpu's? Hmmmm

[Igor]

HD's are by far the slowest things computers have.. aside from printers .
If you want more speed go intp RAID 0. This will impore the speed. Also going SCSI will help, specialy if you get thouse 15,000 RPM Drives.
But for the real boost in performance we gotta wait 'till solid state HD's will get to the market for any1 who has less then a spare million sitting around

[Raptor^]

This is an interesting question
I assume we're talking standard PC hardware here.

This very much depends on the sort of application that your running.

For example in my old job I was dealing with 3d scenes containing 100s MB of textures on screen at once and 1000s of polygons. Here the limiting factor for a standard PC was the speed of the AGP bus, even with 4X AGP it was simply slow. If you went to an area where the textures fit in the memory of the card, performance would suddenley increase.
The SGI320 and 540 PCs could texture directly from main memory and performed much more consistently.

I can also claim that memory bandwidth (more important than, but linked to FSB). If I'm running a sorting algorithm on data that will fit in RAM, then my memory bandwidth will certainly limit the speed of execution.

IMHO in normal use the HDD only becomes a limiting factor if you don't have enough RAM. If your limited by the speed of your disk, buy some more memory instead of a new processor.

HDDs do limit performance during startup and for the first time you load an application, but to me these are unimportant as they occur relatively rarely and are not performance critical.

I think of removeable media in the same way. If I install something from CD, for example, I know I'm only going to do it once and then the speed of the CD drive becomes irrelevant.

CPU speed can still be the limiting factor if you are running an application with a very tight innermost loop. If this loop fits the in L1 cache, then the processor will be running nearly flat out. Even if it misses the L1 and hits the L2 cache we can consider the processor the limiting factor as the L2 cache tends to be on die now. It is only if we get a complete cache miss and have to go across the bus to RAM that everything slows down.

So, where have the performance increases been recently?

Advances in CPU are most obvious, along with those in 3D gfx cards. Both have been pushing Moore's Law recently.

Memory bandwidth certainly hasn't improved vastly over the last few years, so in the general case this would probably be my choice. My 'old' P2-400 has exactly the same memory bandwidth as my p3-700 at its default FSB, yet the processor speed has almost doubled.

HDDs have increased in capacity at an astounding rate recently, but have not got significantly quicker in real life situations, especially if lots of seeks are involved.

CD drives have hit a plateau in terms of performance, but DVDs are significantly fastre. I'm not even considering floppy disks

In a general situation, I think that memory bandwidth is now the limiting factor in a PC. Advances in this area have been slow, yet memory is used fundamentally in a PC.
woah this has turned into a monster post... enough of my ramblings for now


[This message has been edited by Raptor^ (edited October 10, 2000).]

[Humus]

The biggest bottle neck is Microsoft. They keep add new fancy features into the OS and software that we have to learn how to disable. If they would stop adding useless stuff and work for a year or two on increasing performance and removing some bugs I'd be more than happy.

The next bottleneck is system memory, with DDR the situation will be better and will perhaps hold for a couple of years. I hope FC-RAM becomes mainstream until then.

Originally posted by Ymaster:
Now that I think about it..Why not add on-die cash to the Gpu's? Hmmmm

On-die cash? Would be nice ...
I Guess you mean on-die cache ... they already have this, all graphic cards out there have a texture cache and a vertex cache.

[zombor]

any os on a pc will be just as slow, reletavly, to any windows os. And even with ddr memory, it still wont be even as close to as fast(along with the FSB) as the proc.

------------------
Compaq Armada E500
650MHz PIII 128MB RAM
8MB ATI rage mobility
11GB hard drive/DVD
dual booting win98/2k

who said you cant game on a notebook????

[Adisharr]

I would have to vote for the system bus. We are still running that relatively slow compared to other devices in the system. You can almost factor HD's out of the equation if your lucky enough to have enough memory. We really need some type of high speed, very wide data bus with very little latency. That would at least put the monkey back on processors somewhat.

$ .02

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[Sol]

Originally posted by Adisharr:
I would have to vote for the system bus. We are still running that relatively slow compared to other devices in the system. You can almost factor HD's out of the equation if your lucky enough to have enough memory. We really need some type of high speed, very wide data bus with very little latency. That would at least put the monkey back on processors somewhat.

$ .02

Yeah, i have to agree with this. The data still has to travel accross the busto get from component to component.

[Moridin]

The thing limiting PC performance is a basic rule of economics. "The law of diminishing returns". Any time you add a new technology you see an immediate jump in performance. Over time the tech is perfected, expanded and extended, but each subsequent change yields smaller gains then the previous iteration of the technology. I may make a separate post about some of these "new" technologies that have allowed processors to keep pace.

A prime example of this would be 3D acceleration. The jump from no 3D to the first 3DFX chips was huge in comparison to the change between generations of GPU's now.

Every once and a while we reach a point where improvements in a given area become so difficult that that area begins to lag behind the rest of the system and changes to the whole system architecture are necessary to compensate. Two (relatively) recent examples of this are Ram and motherboards (I'll talk a little more about motherboards in another post). A lot of the design features we see today are dictated by this limitation so I consider these the limiting hardware factor.

HDD are not really a problem since if you have enough memory most consumer apps only use them during startup or when they save data.

I would also like to add that I disagree with some statements made about moors law. Moore's law is specific to speed and complexity of integrated circuits including MPU's; it says nothing about overall performance. It turns out that increased complexity of MPU's have offset limiting factors in other areas keeping IPC high while clock rate increased. As a result absolute performance has matched or bettered Moore's law, but Moore's law does not specifically address performance.

I would also disagree with the statements that performance gains have accelerated in the last 2 years. This may be true for the x86 world but if you look at the cutting edge of processor design (the highest performing processors) the opposite is true.

[zombor]

i was just thinking about this in class:
what if someone built a PC that was all on die exept for the hard drive off course. Think about it...the proc would have direct access to the gpu, the ram, sound card, everything...sure you wouldnt be able to upgrade it at all, but wouldnt it be alot faster than having to go thru busses to et to everything? Just an idea

------------------
Compaq Armada E500
650MHz PIII 128MB RAM
8MB ATI rage mobility
11GB hard drive/DVD
dual booting win98/2k

who said you cant game on a notebook????