Original Link: https://www.anandtech.com/show/646
AMD Socket-A 133MHz FSB/DDR Overclocking Guide
by Anand Lal Shimpi on November 1, 2000 1:11 AM EST- Posted in
- CPUs
Two days ago AMD introduced the first DDR platform for the Athlon, the AMD 760 chipset. The reaction to the introduction brought about mixed feelings, while some found the 10% improvement in performance to be nothing to write home about, others were more than pleased. For those that weren’t overly impressed with the chipset, there’s something else about the chipset that may turn you on a bit more than you were initially.
Remember back to the days of the Celeron 300A? The CPU, originally clocked at 300MHz (66MHz x 4.5) made the perfect overclocker as the core had no problem running at 450 – 500MHz. However the Celeron was one of the first Intel CPUs to boast a multiplier lock, thus the only way to overclock the CPU was to use a higher FSB setting. The official 100MHz FSB setting on the BX chipset was perfect as quite a few users bought this 300MHz chip and simply set their BX boards to 100MHz in order to have a “blazingly fast” 450MHz system that rivaled the performance of the most expensive Pentium IIs. This is one of the best ways to overclock since you aren’t running the system bus nor the memory bus out of spec, which limits the only component being overclocked to your CPU, and if your CPU can handle it, then you’re in the clear.
Unfortunately FSB overclocking hasn’t been all too possible on the Athlon platform. The AMD 750, VIA KX133 and KT133 chipsets all supported only one FSB frequency, that was the 100MHz setting that everyone ran at. The chipsets weren’t designed to work with the 133MHz FSB setting and most of the time, motherboards based on these chipsets wouldn’t be able to go any higher than around 110MHz. Luckily for the overclocking population, through the use of Gold Finger Devices like the Afterburner and the K7 Overclock card we were able to manipulate the clock multiplier of the Athlons. Even the newest Athlons and Durons can have their multipliers adjusted through a very simple trick involving some of the “Bridges” on the CPU and with motherboards that support the multiplier adjustment features.
But as we just alluded to, the AMD 760 chipset brings another overclocking possibility to Athlon and Duron users, the ability to use the 133MHz FSB. Just like we could boost the Celeron 300A’s to 450MHz using the officially supported 100MHz FSB on most BX boards, the 133MHz FSB on AMD 760 boards will allow us to do the same to a handful of Athlons and Durons.
This guide will focus on some of the basics of Athlon overclocking since we haven't really devoted a full article to that yet, some warning signs to look out for when overclocking the Athlon/Duron, and finally the performance you can get from overclocking your Athlon/Duron using the 133MHz FSB on AMD 760 based boards.
Multiplier is still the best way to overclock
While the 133MHz FSB may be a nice addition to our overclocking arsenal, the best way to overclock is still by adjusting the clock multiplier. The reason is simple, if you have an 800MHz Duron and attempt to overclock using the 133MHz FSB alone you are placing the success or failure of your endeavor on whether or not your 800MHz CPU can hit 1066MHz. If it does work at that, then you’re in luck, but chances are it won’t, in which case you have no other options. With adjusting the multiplier however you can try your 800 at 100MHz x 10 (1000MHz) or 950MHz or even just 900MHz if you don’t have the highest quality core.
So how do you prepare your CPU to adjust the multiplier?
The first requirement is that you have a motherboard with multiplier adjustment support. We are familiar with the VIA KT133 boards that support multiplier adjustment (ASUS A7V, ABIT KT7-RAID, Microstar K7T Pro2, etc…) however with no available AMD 760 boards it’s difficult to recommend an overclocker’s board to keep your eyes on.
From talking with FIC, it seems like the AD-11 may have multiplier adjustment when it’s released and it wouldn’t be surprising to see ASUS’ A7M266 and the upcoming ABIT 760 boards to have multiplier adjustment features as well. Now you don’t have to have a board that can do this, because there is a way to manipulate your CPU using a precise cutting tool to change its multiplier, but this method is much easier and isn’t nearly as risky.
After first making sure that your motherboard supports multiplier adjustment, you have to then unlock your CPU, which basically allows it to accept any multiplier given to it by the motherboard.
The way to tell if your CPU is unlocked or not is quite simple, if you take a look at your CPU you’ll see seven total location markers, L1 – L7. Next to each one of these markers is a group of little gold dots, some of them may be connected to each other, others may be standing alone. You can think of these “dots” as having the same function as the pins of a jumper, and what you’re going to have to do is simply make the connection between a few of these “pins” in order to unlock your CPU.
You will want to focus on the dots near the L1 location marker. After the L1 label there is a single dot (you won’t do anything with this) followed by four dots on the left and four dots across from them. Your job will be to connect or bridge the gap between the dots on the left and the corresponding ones on the right. Doing so will effectively unlock your CPU.
You need something that can make an electrical connection between those two points. A soldering iron won’t work because solder won’t adhere to the surface of the CPU. The best option here is to use some sort of conductive ink.
In the lab we use a circuitworks conductive pen (model number CW2200MTP) and we simply unscrew the top of the pen and place a small amount of conductive ink on the tip of a fine needle and use that to form the bridges.
You can also put some conductive ink on the tip of a mechanical pencil or actually on the lead of a mechanical pencil if that’s easier for you.
Others have been using the conductive properties of the graphite in pencil lead to make the connections. This works fine too as long as you’re using a pencil with the proper type of lead, however we don’t recommend this method for anything other than quickly testing to see if it works. Using the wrong type of pencil lead can cause the connection not to be made and failure to unlock the CPU.
We’ve received a lot of requests for where you can find conductive pens, if you visit www.chemtronics.com they have a reseller locator, just search for the reseller closest to you. The pens run around $10, and it’s a much better way of unlocking your CPU.
Also when you're making these connections make sure that you don't let any of the conductive ink bleed over to another connection, since this is potentially damaging to your CPU.
Correct
|
Incorrect
|
If your motherboard doesn’t support voltage adjustment, you can use the same bridging technique at location L7 to change the voltage of your CPU.
Remember that all of the current line of Athlon processors run at a 1.75v core voltage setting by default. Earlier chips may be spec'd to run at lower voltages, but all newer ones should be rated at 1.75v.
For Duron owners, all new Duron CPUs run at a default 1.60v, but if you plan on getting a Duron up to the higher clock speeds you'll want to probably bump the voltage up to at least the 1.75v level which, as we just mentioned, is the default for the newer Athlons.
Ideally you will have a motherboard that offers voltage adjustment either on the board or preferrably in the BIOS, keep a look out for upcoming motherboard reviews that feature these new DDR/266MHz FSB chipsets for the Athlon here on AnandTech, we'll make sure you know which ones give you the features you want and which ones fall short.
Multiplier + FSB is an even better way to overclock
So you have a 800MHz processor that hits 1GHz, but what’s better than running at 100MHz x 10.0? You guessed it, running at 133MHz x 7.5. Both settings yield a 1GHz overclock, however with the latter you are running your FSB at a 33% higher frequency, not to mention your memory bus now runs at a 33% higher frequency as well. This translates into 1/3 more memory and system bus bandwidth allowing you to make much more out of your overclocked CPU than before.
Since we are doing all of this overclocking on an AMD 760 platform with DDR SDRAM, if you want to try it you're going to want to make sure that your DDR SDRAM can run at PC2100 speeds (133MHz DDR) otherwise you'll definitely run into some problems.
There are a couple of sweet spots when dealing with Multiplier + FSB overclocking, the two we will talk about in particular involve the 7.5x multiplier and the 133MHz FSB.
Perfect
Overclockers
|
|||||||||||
CPU
|
FSB
Frequency
|
Clock
Multiplier
|
|||||||||
Athlon 750MHz |
100MHz
|
7.5x
|
|||||||||
Duron 750MHz |
100MHz
|
7.5x
|
AMD currently has 1GHz Athlons available, and we have already seen Durons overclocking to 1GHz levels and sometimes beyond that, so it makes sense that an overclock to 1GHz is pretty reasonable. The two chips that were made for this overclock are the Athlon 750 and the Duron 750. Why? Because they both have a 7.5x hard coded multiplier, and simply switching to the 133MHz FSB will yield a 1GHz clock speed, provided that your CPUs can handle it.
If they can't, you can just as easily drop the clock multiplier to 7.0x or 6.5x while keeping the 133MHz FSB. And as you're about to see, the 133MHz FSB is definitely worth it over a small clock speed drop if necessary.
Let's take a look at the currently available Athlon and Duron CPUs, their clock multipliers, and see which speeds we should aim for in general with this type of overclocking.
Overclocking
Possibilities
|
||||||||||||
CPU
|
Clock
Multiplier
|
Original
(100MHz FSB) Clock Speed |
Overclocked
(133MHz FSB) Clock Speed
|
|||||||||
Athlon 650MHz |
6.5x
|
600MHz
|
866MHz
|
|||||||||
Athlon 700MHz |
7.0x
|
700MHz
|
933MHz
|
|||||||||
Athlon 750MHz |
7.5x
|
750MHz
|
1GHz
|
|||||||||
Athlon 800MHz |
8.0x
|
800MHz
|
1.07GHz
|
|||||||||
Athlon 850MHz |
8.5x
|
850MHz
|
1.13GHz
|
|||||||||
Athlon 900MHz |
9.0x
|
900MHz
|
1.2GHz
|
|||||||||
Athlon 950MHz |
9.5x
|
950MHz
|
1.26GHz
|
|||||||||
Athlon 1GHz |
10.0x
|
1GHz
|
1.33GHz
|
|||||||||
Athlon 1.1GHz |
11.0x
|
1.1GHz
|
1.46GHz
|
|||||||||
Athlon 1.2GHz |
12.0x
|
1.2GHz
|
1.6GHz
|
|||||||||
Duron 600MHz |
6.0x
|
600MHz
|
800MHz
|
|||||||||
Duron 650MHz |
6.5x
|
650MHz
|
866MHz
|
|||||||||
Duron 700MHz |
7.0x
|
700MHz
|
933MHz
|
|||||||||
Duron 750MHz |
7.5x
|
750MHz
|
1GHz
|
|||||||||
Duron 800MHz |
8.0x
|
800MHz
|
1.07GHz
|
The numbers in Red are the ones that aren't too realistic expectations, not with conventional cooling or based on AMD's current yields. The bold numbers in the last column, however, are fairly reasonable goals to shoot for. And using the multiplier adjustment techniques we discussed earlier, if you have a Duron 800 for example and aren't able to hit 8.0 x 133MHz, then you can simply decrease your multiplier (assuming you have a board capable of doing that) to 7.5x or 7.0x and still maintain a good speed increase.
As we mentioned earlier, the two CPUs we'll be focusing on will be the Athlon 750 and more importantly the Duron 750. Why do we saw more importantly? Well, the Duron 750 currently sells for $90 - $100 boxed, or $70 - $80 for OEM parts. Not too bad for something that has the potential to run at 1GHz.
The Risk
As with any sort of overclocking, you're taking a risk at damaging your hardware. There is no question about the fact that you're shortening the life of your CPU by overclocking. If you're shortening its life from 10 years down to 2 years it's obviously not as big of a deal as it would be if you were cutting its life down to 2 months. While we take no responsibility for what happens to your hardware from overclocking, we can offer you some suggestions to help make your overclocking attempt a success.
Don't push the voltage too far. According to AMD, the maximum voltage for Athlons is 1.85v and 1.70v for Durons. Since they are both essentially based on the same core and come out of the same fab we can say that the Duron is safe up to 1.85v as well, the reason for the difference in maximum voltage there is because with the Athlons you have to worry about maintaining a high yield on twice as much cache, thus the need for a higher voltage (the more voltage you supply, the higher the yield as you're giving the CPU a greater tolerance range to work in).
Keep a careful eye on your core temperature. It is normal for 1GHz and faster Athlons to run at temperatures in the low 50s (Celsius), however by using a recommended heatsink/fan you can easily keep your CPU running in the 40s or maybe the high 30s. If your core temperature ever gets above 60C then you have reason to be worried. While that's within the CPU's operating limits, none of the currently available Athlons should ever run that hot if you're using proper cooling.
Something we discovered while reviewing cases not too long ago was that as long as you have a well ventilated case (i.e. not a cramped mini-tower) and you have a decent heatsink/fan for your CPU (we use the TaiSol unit pictured here) adding additional fans to your case won't help decrease your core temperature by any measurable degree. The only time you'll need to add extra fans is if the air being circulated inside your case is too hot to be doing any good. For even the fastest Athlon systems with a well designed case and a good heatsink on the CPU, all you should need in terms of additional cooling is another intake or exhaust fan placed at either the front or back of the case depending on its function (intake at the front, exhaust at the back).
Another big issue regarding Athlons and Durons that isn't related to overclocking directly is the issue of "crushing" your core when mounting your heatsink on the CPU. In order to dissipate the 60W+ of heat that the fastest Athlons are producing, heatsink manufacturers have resorted to producing some very large heatsinks. But in order for these heatsinks to actually serve a useful purpose they must make good contact with the core. If you've ever seen an Athlon or a Duron, you'll quickly realize that getting such a great amount of heat away from such a small surface area isn't an easy task.
By applying a large amount of pressure to the top of CPU the heatsinks can make good contact with the core, unfortunately this means that it takes a large amount of pressure on your part to get the heatsink attached to the CPU socket. In some cases, by applying uneven levels of force while attaching the heatsink to the CPU socket users have actually cracked or crushed their cores.
The only way to avoid this is to follow the age old axiom, slow and steady wins the race. Attach one end of the heatsink clip to the socket, reposition the heatsink if it moved at all, and apply pressure to the other end in order to get it to latch.
It often helps to use a flat head screwdriver to give you some leverage in making the other end of the clip hook onto the socket. Simply slide the flat head into the little hook on the end of the clip bend outwards and push down at the same time to the point where you can let go and the clip will attach itself to the CPU socket.
The CPUs
Instead of going through a handful of CPUs to find some that would work to illustrate our purposes we dropped an email to 'Da HeadNut' over at PCNut.com to see if they had any pre-tested CPUs in stock. It turns out that they had two, a Duron 700 that was guaranteed to work at 950MHz (1.85v core) and an Athlon 750 that was guaranteed to work at 1GHz (1.85v). While the Duron 700 wasn't exactly what we were looking for, the Athlon 750 was perfect. The Duron 700 capable of hitting 950MHz would be perfect if are we were interested in was hitting 933MHz (7.0 x 133MHz = 933MHz) however we wanted to do a 1GHz comparison between the Duron and the Athlon in addition to our overclocking experiments.
Luckily one of our Duron 750's hit 1GHz at 1.85v without a hitch which was perfect for what we needed to do. So if you don't want to take the risk of getting a CPU that might not make it as high as you'd probably want to pick up a pre-tested CPU. PC Nut is a vendor we trust so drop by their site at www.pcnut.com if this is something you're interested in. They shipped the CPUs to us pre-tested and already unlocked using the pencil trick, although we would rather they have used conductive ink to do the job.
They're not an AnandTech sponsor, but you can consider them to be an AnandTech recommendation.
PCNut's Athlon 750 guaranteed
at 1GHz @ 1.85v
PCNut's Duron 700 guaranteed
at 950MHz @ 1.85v
AnandTech's Duron 750 stable
at 1GHz @ 1.85v
The Test
Windows 98SE / 2000 Test System |
|||||
Hardware |
|||||
CPU(s) |
AMD Duron 750
|
AMD Athlon "Thunderbird" 750 |
|||
Motherboard(s) | AMD Corona EVT8 (AMD 760 Reference Board) | ||||
Memory |
256MB PC2100 Micron DDR SDRAM (CAS 2.5) |
||||
Hard Drive |
IBM Deskstar 30GB 75GXP 7200 RPM Ultra ATA/100 |
||||
CDROM |
Phillips 48X |
||||
Video Card(s) |
NVIDIA GeForce 2 GTS 32MB DDR (default clock - 200/166 DDR) |
||||
Ethernet |
Linksys LNE100TX 100Mbit PCI Ethernet Adapter |
||||
Software |
|||||
Operating System |
Windows
98 SE AMD BMIDE Drivers v1.32 & AGP Drivers v5.21 were used under both OSes |
||||
Video Drivers |
|
||||
Benchmarking Applications |
|||||
Gaming |
Unreal
Tournament 4.32 Reverend's Thunder.dem |
||||
Productivity |
BAPCo SYSMark
2000 |
We start off with Linpack to see exactly what the 133MHz FSB and 133MHz memory bus (both DDR) buys us over the regular 100MHz FSB and 100MHz memory bus we were starting off from in a non-overclocked state. As you can probably guess, the 33% increase in clock speed increases the raw performance of the CPU in this test by 33% as long as the data set is small enough to fit within the 64KB L1 Data Cache or the 256KB L2 cache of the Athlon. After that, the performance advantage drops off to 25% and below as the data set continues to increase in size.
Looking at the Duron's Linpack graph we notice a similar performance trend. While the data set is small enough to fit within the Duron's 64KB L1 Data Cache the performance improvement our overclocked processor offers is 33%, which is a 1% per MHz increase in performance. However, since the Duron doesn't have as large of a L2 cache as the Athlon the performance drops off much sooner than what we noticed on the Athlon.
If we step back and look at how all of the graphs compare, it seems as if the un-overclocked Athlon 750 eventually will outperform the Duron at 1GHz as the amount of data you're dealing with increases. The sweet spot for the Athlon when running against the Duron is in the 64KB - 256KB range where the Duron's performance drops off severely because of its 64KB L2 cache.
So is the Athlon 750 faster than the overclocked Duron at 1GHz? If you are in a situation where your application can't fit within the Duron's L2 cache but it can fit within the Athlon's L2 cache you'll find that the Athlon 750 can be faster than the overclocked Duron at 1GHz. However the majority of cases you'll encounter won't be like that, so to see how the chips stack up let's take a look at what happens when you're dealing with a lot of data, more than can fit in either CPU's cache.
The overclocked 1GHz Athlon comes out on top obviously, but if you'll notice the Duron overclocked to 1GHz levels off in performance since it's using the same memory bus/FSB as the 1GHz Athlon. This also helps it to outperform the Athlon at 750MHz because in this test, the Athlon is limited to PC1600 DDR SDRAM speeds (100MHz x 2). For more information on why it's limited to PC1600 because we're using the 100MHz FSB here, read our AMD 760 Review - it is a chipset limitation, and for good reason.
So now that we know what to expect in theory, let's see what happens in the real world performance tests.
Both the Athlon and Duron enjoy a 16% performance boost because of the increased clock speed, FSB frequency and memory bus frequency. And we see that the Duron does in fact follow our Linpack results, at 1GHz it does outperform the Athlon 750 as we'd expect it to.
This isn't the case with Intel's Celeron which, even at 1GHz, has difficulty competing with the Pentium III 750. We'll let you think about why and answer that question in our next Celeron review.
At 1GHz the Athlon holds a 5% performance lead over the Duron at the same FSB/clock speed. If you look back at our original Duron review, back then we noted a 6% performance differential between the Athlon (Thunderbird) and the Duron at equivalent clock speeds, it looks like we're seeing the same thing here.
We see an even larger performance boost under MDK2, approximately 20% for both the Athlon and the Duron. In terms of the Athlon vs Duron comparison at 1GHz, the Athlon comes out with a 6% performance advantage which is in-line with our Quake III Arena scores.
Our third FPS benchmark, UnrealTournament, illustrates a 15 - 16% performance boost because of our 'little' overclock. This is virtually identical to the performance improvement we saw under Quake III Arena which makes sense since UT is a very similar game. However the performance difference between the Athlon and the Duron extends to close to 10% here. Considering the price of the 750MHz Duron that we overclocked to 1GHz though, that 10% becomes very small, very quickly.
Expendable has always been a good cache/memory test, and we can see the results of that with the 20% increase in performance we saw under this test.
Finally, the Athlon at 1GHz comes out a full 11% faster than the Duron at 1GHz. But once again, when you factor in price the 11% performance difference loses a lot of attention.
Even in Office and Content Creation applications, which SYSMark 2000 puts to the test, the 1GHz Duron doesn't fall into the one exception we found in the Linpack tests where it would actually be slower than the Athlon 750. It just goes to show you that the chances of that happening are very low.
Under SYSMark 2000 the Athlon at 1GHz, once again, showed an 11% performance advantage over the equivalently overclocked Duron.
Here's something interesting. In theory, the Duron should have been showing a greater performance increase by moving to the faster memory/FSB than the Athlon because it has more to gain from a faster memory bus (as we showed in our Linpack benchmarks because of its smaller L2 cache). However up until this point that hadn't come true.
Content Creation Winstone 2000 is a benchmark that focuses on multitasking, running multiple office and content creation applications, such as MS Word and Adobe Photoshop, at the same time. As you can guess, and as we saw in our AMD 760 Review, this is where a faster memory bus and FSB can truly shine. This is also where the Duron's ability to gain more from the faster DDR memory can be seen, although the performance delta it produces is much smaller than what we originally expected.
Here the Athlon is only 2% faster than the Duron when they're both overclocked to 1GHz using the 133MHz FSB.
High End Winstone 99 differs from CC Winstone 2000 in that it only runs a single application at a time, however the type of applications that it features are much more cache/memory bandwidth intensive along with much more FPU intensive than what we saw in CC Winstone 2000.
Because of this, performance analysis is pretty much the same as above, however the performance difference between the Athlon and the Duron at 1GHz is extended to 6% which still isn't bad at all.
For those that deal with professional level 3D graphics, as long as you have a powerful graphics card (in this case the GeForce2 GTS does just fine) you'll be hard pressed to tell the difference between an Athlon and a Duron, even while overclocked. This is one of the beauties of the Duron, even as its clock speed increases the CPU can still be used as a cheaper alternative to the Athlon and the Pentium III; and in many cases, without offering lesser performance.
Final Words
Not only has the AMD 760 chipset opened up the path for the Athlon and Duron line of processors to continue to scale wonderfully with clock speed, but it has also opened a new avenue for overclockers to experiment with. The combination of the 133MHz FSB with the right clock multiplier can yield a very high performing CPU without a high price tag.
The sweet spots, as we discussed in the article, are those CPUs that can realistically hit 900 - 1000MHz clock speeds yet reside in the 650 - 750MHz default operating frequency range. The reason being that you can simply crank up the FSB and watch the performance fly, however in many cases you're going to have to play around with the CPU's clock multiplier alongside the FSB in order to get the most out of your system.
There is no doubt that at least some of the AMD 760 boards that will be surfacing shortly will feature the necessary clock multiplier, voltage and FSB adjustments to make overclocking on this new platform as easy as possible.
The only potential problem may exist in how AMD decides to differentiate the 100MHz FSB Athlon/Duron processors from the newly released 133MHz FSB processors. According to AMD, the FSB will be set by the bridges on the top of the CPU, but which bridges is a yet unanswered question. We haven't been able to figure it out yet but we'll keep on digging to see what we can uncover.
Until then, get ready because AMD has just made overclocking not only much more viable of an option, but much more fun as well.