OT, But interesting

[Tim Schmidt]

>From: Sean <picasso@madflower.com>
>To: Tim Schmidt <computer_holic@hotmail.com>
>CC: linux-user@egr.msu.edu
>Subject: Re: OT, But interesting
>Date: Sun, 6 Aug 2000 14:16:11 -0400 (EDT)
>
>Does AMD use IBM's Copper technology? I know Intel licensed the Copper
>Technology with the "coppermine" series,

Actually, Coppermine is a misnomer.  All Intel chips currently use aluminum 
technology.  AMD is still using Aluminum tech at it's Texas foundry where 
all Durons and a few Thunderbirds are being produced, AMD is using copper 
tech (dunno if it's liscenced from IBM) at it's Dresden plant in Germany 
where most of the Thunderbirds are being produced as well as all of the 
upcomming Corvette mobile Athlons.

>but Its a bit tricky to get it to
>work right especially with large chips. IBM is having a hard time getting
>it to work correctly with the G-4 series chips which have 2.5  times more
>transistors then the G-3 series does.

AMD's Copper Thunderbirds (some un-godly ammount of transistors, like 3x as 
many as the G4) are working beautifully.

>
>The copper technology rocks.  They took the G-3 300 design, shrank the die
>from .20 to .18 and lowered the voltage and upped the clock to I believe
>400MHZ and basically ended up with a faster chip that used less energy. (I
>think it was from 6watts to 3.5watts.) This is why Apple can ship the
>_real_ G-3 chip in its portables and not some cut down version like the
>"mobile series". Also, its why if you get a desktop box, your more likely
>to get a motorola chip (which I believe still uses aluminum) and if you
>get a portable your more likely to get an IBM chip. It's also part of the
>reason why they are shipping machines without cooling fans(iCube, iMac).

Yes, the lowering of voltage and wattage sed is a product of the die shrink, 
using copper instead of aluminum apparantly won't make much of a difference 
with .15, and will only start to show up when .13u chips hit shelves.  The 
Thunderbirds use anywhere from 30 to 45W depending on speed.

>
>As far as stamping the speeds on the chips, IBM/Motorola looked at the
>demand before stamping the chips. If they made a batch with a great yield
>of 500MHZ chips, some of those might get stamped as 400MHZ just because
>they were out of the 400MHZ chips. Which increases the chances of being
>able to overclock them significantly. I dont know if Intel or AMD uses the
>same technique or not.

Yes, all fabs do.  including everything from graphics processors to memory 
(assuming there's more than one speed grade available).

>
>Clock chipping (overclocking just the chip) has traditionally been
>unstable and never resulted in major _real_ performance gains. Its a
>little different story then overclocking your entire board as far as the
>benefits.

On PC's, OC'ing the chip can yield --massive-- benefits, like a 25-45% 
performance increase (Duron 600Mhz -> 950Mhz).

>
>This throws out a couple of questions.
>First MHZ to MHZ do the AMD and Intel chips stack up equally as far as RL
>performance?

Yes and no.  Here's the breakdown:

Both AMD and Intel have a "flagship" and a "value" chip.  They both use the 
same respective core, the only difference is (front side) bus speed and L2 
Cache configuration.  AMD's Core is equal to Intel's in RW performance 
except in FP where it's about 30% faster.


Duron vs. Celeron

The Duron is approx 25% faster than the same speed Celeron, here's why:

-Duron: L1: 128k  L2: 64k  exclusive design (64bit bus, 16-way)
-Celeron2 (Celermine): L1: 32k  L2: 128k  inclusive design (256bit bus, 
8-way)

As you can see, the Duron has 32k more cache, and more of it's cache is 
closer to the core.  The duron however, has another advantage and that is 
that info in the L1 does not have to be duplicated in L2 but the Celeron's 
L1 has to be duplicated in L2...  Effectively giving the Celeron 96k of L2 
and pusing the Duron to 64k more cache than the Celeron.

Thunderbird vs. Coppermine

The Thunderbird is significantly faster than Coppermine at lower speeds (ala 
600Mhz), but at 1Ghz, they score about equal with Coppermine coming out on 
top in slightly more benchmarks.  This is due mainly to the Coppermine's 
superior L2 Cache design.

-Thunderbird: L1: 128k  L2:256k exclusive design (64bit bus, 16-way)
-Coppermine: L1: 32k  L2:256k inclusive design (256bit bus, 8-way)

As you can see, the Thunderbird has 128k more cache (counting the 
inclusive/exclusive design) than the Coppermine, The Thunderbird is even 
more likely to find what it needs in it's cache (16-was assosciative, 
divides the cache into 16 different caching sectors).  However, the 
Coppermine has 4x the bandwidth to it's L2 Cache, making it nearly as fast 
as L1.

>
>If Intel is disabling some unstable code, could this be some of the code
>specifically on the chip for the SPEC tests (Intel has a set of
>instructions on the chip specifically written for the SPEC tests and
>only used for that)?

Possible, you'd have to ask an engineer.

>
>If the internal clock speed of the Pentium is running at 100MHZ what
>is the benefit of clocking the rest of the chip to 1ghz? Your still
>processing information internally at 100MHZ.

Coppermine's run at 133Mhz FSB (Front-side bus), that's the speed of the bus 
it uses to communicate with memory, PCI/AGP busses.  The Athlon/Duron family 
runs at a 100Mhz DDR bus (effectively 200Mhz) soon to be increased to 266Mhz 
(133Mhz x2), the upcoming P IV Willamette runs a 400Mhz bus (Really 100Mhz 
x4 like mega-DDR).  The Wilamette takes a RISC-esque approach that will be 
it's downfall however, instead of adding transistors for parallel processing 
(called super-scalar design) it drastically reduces the number of 
transistors and lengthens the pipeline (to 20 stages, as compared to the 
Athlon's 13 stages and the PIII's 11).  This allows the chip to be run much 
cooler and hence clocked much higher, but it also --drastically-- reduces 
performance in the real world.  It appears as if Intel is trying for the 
crowd that looks at the Mhz rating, in essence, they're pullig a similar 
trick to Cyrix's PR ratings.

>
>This in my mind throws out the question so what if it the chip is running
>at 1GHZ or 1.1GHZ? You are better off with a 1GHZ chip on a 200MHZ board
>(or running your 1.1GHZ chip at 1GHZ). This is simply because of the wait
>states involved. If you have a 200MHZ board with a 1GHZ chip and your
>66MHZ PCI bus. You have an even 1:3 ratio between the PCI and the board
>and an even ratio of 5:1 between the chip to the board. This translates
>into NO wasted time for parts of a clock cycle. Your chip is running 15x
>the PCI bus.

PCI bus in PC's run's at 33Mhz @ 32bit.  Some super-high end 
Workstation/server boards have 66Mhz 64bit PCI.  The Intel chip @ 1133Mhz 
runs an 8.5x multiplyer (8.5*133 = 1133) However, AMD's 1.1Ghz Athlon runs a 
5.5x multiplyer (5.5*200 = 1100 (really an 11x multiplyer: 11*100 = 1100, 
but effectively 5.5))  You are correct that this puts AMD's chip in a much 
more favorable position.  PC's are generally not run asyncronously.  The 
only exception is VIA's recent chipsets (and Intel's i815) which allow you 
to run your SDRAM either 33Mhz hieher or lower than the system bus speed.  
Tests have shown that running it 33Mhz faster doesn't make much of a 
difference (on the order of 1 or 2%), and slower slows it down about 5%.

>
>If your running at 1.1ghz you have the 1:3 ratio between the PCI and the
>board, and a 5.5:1 ratio between the chip and the bus. If the buses can
>only exchange data when the cycles match, you are actually waiting for the
>chip to go around to the 11:2 ratio, the extra wait time involved actually
>slows your machine down unless you are performing 11 instructions on
>every piece of data.

Incorrect.  Deep buffers are used to hold information until the other bus is 
ready, however, this is only used in a few chipsets as mentioned above.

>
>Or am I completely offbase?
>

Not completely, just slightly.  Put it this way, the engineers are about a 
half step ahead of you ;)

>
>
>  On Sun, 6 Aug 2000, Tim Schmidt wrote:
>
> > >From: "Tim Schmidt" <computer_holic@hotmail.com>
> > >To: linux-user@egr.msu.edu
> > >Subject: Re: OT, But interesting
> > >Date: Sun, 06 Aug 2000 17:03:06 GMT
> > >
> > >>From: Ben Pfaff <pfaffben@msu.edu>
> > >>Reply-To: pfaffben@msu.edu
> > >>To: "Tim Schmidt" <computer_holic@hotmail.com>
> > >>CC: linux-user@egr.msu.edu
> > >>Subject: Re: OT, But interesting
> > >>Date: 06 Aug 2000 10:15:02 -0400
> > >>
> > >>"Tim Schmidt" <computer_holic@hotmail.com> writes:
> > >>
> > >> > http://www.hardocp.com/news_images/2000/aug2k/080500b.html
> > >>
> > >>I'm unable to read that article with lynx, w3m, or links: all I
> > >>get is links to three "IFRAME"s, which just contain ads, no
> > >>content.
> > >
> > >works in Netscape...
> > >
> > >>
> > >> > It appears that Intel is not only factory overclocking their
> > >> > CPUs [...]
> > >>
> > >>Isn't that an oxymoron, or a misnomer?  As I understand it, when
> > >>you go to a chip fab, there aren't separate assembly lines
> > >>cranking out 60 ns and 70 ns, nor are there separate assembly
> > >>lines cranking out 866 MHz and 933 MHz Pentium IIIs, and so on.
> > >>Rather, each chip that comes off the line is tested for its
> > >>performance, where they crank up the speed until it fails at N
> > >>MHz, and then they sell it as an (N - delta) MHz chip.
> > >>
> > >>On the other hand, overclocking is running a chip at a faster
> > >>speed than recommended by the manufacturer.  So the factory
> > >>*can't* overclock chips.  They could recommend that you run it
> > >>faster than it would actually work, I suppose, but in that case
> > >>it's a defective chip and you should be able to exchange for a
> > >>working one.
> > >
> >
> > I was reading over your question again Ben, and realized an even better 
>way
> > to explain why those "questionable tactics" are "factory overclocking."
> > Here it goes.  You're right, whe a chip comes off the line, it's tested 
>to
> > see how fast it can run -- but the testing is done at default settings 
>(in
> > this case, 1.6v, no microcode, stock HSF).  At this point, AMD stamps 
>the
> > speed on them and ships them off.  Intel however, takes the fastest of 
>these
> > chips, ups the voltage (just as any other OC'er is experienced in 
>doing),
> > slaps on a massive HSF, to see how much higher they can get it (in other
> > words, it's being overclocked from it's normal tested rating -- at the
> > factory).  If it doesn't run 100% stable, they write some new microcode 
>to
> > disable whatever part of the processor is giving them problems at that
> > speed.  Of course that's an over-simplification of how microcode works, 
>but
> > you get the point.
> >
> > Did this explain it better?  Why it's refered to as factory 
>overclocking?
> >
> >
> > >Yes Ben, but PIII-C's run at 1.6v (I think, maybe 1.65), Intel has not 
>only
> > >cranked up the voltage (gets a clearer high/low voltage signal through) 
>to
> > >increase the speed the chip can reach, they've issued microcode updates 
>for
> > >the 850 and up which in effect "turn off" parts of the chip that can 
>hold
> > >it
> > >back when reaching higher speeds.  So microcode updates allow the chip 
>to
> > >clock higher, but have a performance hit.  Also, Intel has outfitted 
>the
> > >PIII 1000, and 1133 (and I think the 850 and up) chips with massive 
>HSF's
> > >(Heatsink + fans) to dissipate the massive ammounts of heat produced by 
>the
> > >high clock-speed/voltage.
> > >
> > >In other words, with no tweaking a PIII-C might reach 850Mhz, only with
> > >--massive-- ammounts of tweaking and/or questionable tactics can a 
>PIII-C
> > >go
> > >any higher.
> > >
> > >AMD on the other hand, has not used and microcode updates, voltage 
>hikes,
> > >die shrinks, or massive heatsinks to get teh Athlon to 1Ghz.  1.1Ghz
> > >athlons
> > >have been in the hands of reviewers for several months now also.
> > >
> > >In short, resorting to all these questionable tactics is what is 
>generally
> > >refered to as "factory overclocking"  -- yes, it is technically an
> > >oxymoron.
> > >
> > >--Tim
>

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