Socket 7: Fit For Years To Come!
Редакция THG,  6 ноября 2000

Socket7 Triangle: AMD K6-2, AMD K6-2+ and AMD K6-III+


Many motherboards in old PC systems are still based on socket7. Users with such platforms often look for a cheap way to speed up their aged computer. And indeed, there are ways to replace a slow Intel CPU e.g. the Pentium 90 with a speedy AMD K6 processor. The advantage is that you don't have to replace the motherboard, thereby avoiding complicated mounting procedures. But there is another thing to consider. Almost all older systems are equipped with an AT chassis and AT motherboard. It is almost impossible to find motherboards that still comply with this ancient form factor. But, if you still want to undertake a full upgrade, you'd have to replace motherboard and chassis together with your CPU.

Socket 7
Good old Socket7 is still the platform that many old computers are based upon. Using fast K6 CPUs, you can do a cheap system upgrade without having to change motherboard or chassis.

Socket7 Triangle: AMD K6-2, AMD K6-2+ and AMD K6-III+, Continued

We compared three different AMD CPUs of the same clock speed. The three processors' underlying model is AMD K6-2/500, which has no on-die L2 cache. The K6-2 communicates via a 100 MHz processor bus with its external L2 cache. Therefore, most motherboards are equipped with 512 KB or 1 MB cache modules that sit close to the socket. Some rare motherboards such as the FIC PA-2013 or DFI P5BV3+ even utilize 2MB of cache.

Processor AMD K6-III+ AMD K6-2+ AMD K6-2
Process technology 0,18µm 0,18µm 0,25µm
CPU clock 400 to 500MHz 475 to 550MHz 300 to 500MHz
CPU platform Socket7 Socket7 Socket7
CPU system clock 100MHz 95 to 100MHz 66 to 100MHz
L1 cache 64KB 64KB 64KB
L1 cache access CPU core clock CPU core clock CPU core clock
L2 cache interface 64bit 64bit 64bit
L2 cache 256 KB on-die 128 KB on-die on the motherboard, max. 2048 KB
L2 cache clock CPU core clock CPU core clock 66 to 100MHz
L3 Cache on the Motherboard, max. 2048 KB on the motherboard, max. 2048 KB no
MMX instruction set yes yes yes
3D instruction set 3DNow 3DNow 3DNow
Multiprocessor support no no no
Power saving modes PowerNow PowerNow no
Core voltage 1.4 to 2.0V 1.4 to 2.0V 2.2 to 2.8V
I/O voltage 3.1 to 3.3V 3.1 to 3.3V 3.1 to 3.5Volt
Power dissipitation max. 23W max. 20W max. 29W

Thereґs a fundamental difference between new K6-2+ and K6-III+ CPUs and older K6-2 models. For using up-to-date PowerNow technology, you need a special motherboard with voltage regulator.

Socket7 Triangle: AMD K6-2, AMD K6-2+ and AMD K6-III+, Continued

In contrast to the K6-2/500, the AMD K6-2+/500 as well as AMD K6-III+/500 have full-speed on-die L2 cache under the hood. The only difference is the size. The K6-2+ uses 128 KB while the K6-III+ has 256 KB. Integrated L2 cache became possible because these two CPUs are manufactured in 0.18-micron process. The old K6-2 is still made using 0.25µ-process. By the way, you don't have to disable the cache modules on your socket7 motherboard. When a K6 processor has on-die L2 cache those external modules function as 'L3 cache', which improve performance a little bit further. We want to emphasize one point right away: AMD has not aimed the abovementioned 'Plus' processors at the end user market. While some retailers offer the AMD K6-2+/500 in small numbers, the AMD K6-III+/500 is exclusively sold to OEMs. Compaq, for example, uses this processor with their cheaper Notebooks. Unlike traditional K6-2 CPUs, the K6-2+/K6-III+ processors are equipped with the power saving technology 'PowerNow', AMD's copy of Intel's SpeedStep technology. This technology enables users to drastically reduce power consumption. Especially in battery mode the CPU clock rate can be slowed down thereby increasing battery running time.


The new AMD K6-III+/500 is shown here, which is the fastest CPU for Socket7! Equipped with an 256KB on-Die L2 cache it reaches impressive benchmark results.

AMD K6-2+

With the exception of a smaller L2 cache (128KB), AMD K6-2+/500 is absolutely identical to K6-III+/500. Both CPUs come with the new PowerNow technology.

AMD K6-2

AMD K6-2/500 is a very good and cheap upgrade solution for older systems based on socket7.

CPU upgrade - which boards support it?

If you want to upgrade old, slow PC systems, several requirements have to be met. First, your motherboard must be equipped at least with socket7. Its predecessor socket5 can also be found in systems dating back to the beginning of 1996, but it cannot be used for an upgrade anymore. Furthermore the right CPU core voltage for these new AMD CPUs is an important issue. A motherboard without a split voltage feature, i.e. separate power supplies for CPU core and I/O, can't be upgraded this way. While AMD K6-2 needs a core voltage of 2.2 volt, brand new K6-2+ and K6-III+ require 2.0 volt and 1.8 volt, respectively. In this case, it depends on the core voltages supported by the voltage regulator on the motherboard. Usually, information about voltage settings can be found in the manual or on the motherboard itself. Still, sometimes manufacturers do not describe all possible settings. Here's a typical example: According to one manufacturer, a given voltage regulator offers a minimum core voltage of 2.1 volt. However, we found that voltages ranging from 1.8 volts to 2.0 volt were feasible as well. Setting these values is often possible using non-documented jumper combinations.

The maximum clock ratio

All motherboards with Socket7 have a maximum clock ratio of 5.5. When it is restricted to an external bus clock of 66MHz, you can't enable the maximum clock rate of 100MHz x 5.5 = 550MHz. Thus a AMD K6-2 would only run at 66MHz x 5.5 = 366MHz. Luckily, AMD put a small logic into their CPUs which enables them to use a clock ratio of 6. This comes into effect if the motherboard clock ratio is set to 2. Starting with K6-2, all CPUs read this setting as 66MHz x 6.0 = 400MHz. Fewer problems occur with motherboards supporting external clock rates higher than 66MHz. With an Abit IT5H, for example, the user can set 83MHz x 6.0 = 500MHz and use an AMD K6-2/500 or K6-2+/500 at their maximum rating. Still, only very few motherboards with Intel 430HX chipset support external clock rates of 75 MHz or 83 MHz. In our table, we show some widely used motherboards, which can be upgraded.


No chance without cooling. Successful overclocking is only feasible with perfect heat sinks. We used a copper version with heavy-duty fan. This made AMD K6-III+/500 run at a whopping 600 MHz!

Overclocking: Cooling And Voltage

Overclocking of Socket7 systems is quite an interesting topic. Apart from increasing external clock rate and clock ratio, other important steps must be taken to ensure successful overclocking.

First of all, the core voltage has to be increased very carefully. The AMD K6-III+/500, for instance, has to be run at a maximum core voltage of 2.0 instead of the official 1.8v.

Better performance has then its price. The greater amount of heat radiated from the CPU has to be dissipated with a powerful heat sink and fan. A standard heat sink solution usually is not sufficient. We recommend a combination of a copper heat sink and high-speed fan with a minimum of 5000 rpm. We'll publish a test of heat sinks and fans in the near future for those who are more interested in this issue.

Board Platform Chipset Max. System Bus CPUs
Asus P55T2P4 Socket7 Intel 430HX 83MHz AMD K6-2/500,
Abit IT5H Socket7 Intel 430HX 83MHz AMD K6-2/500,
Gigabyte GA-586HX Socket7 Intel 430HX 66MHz AMD K6-2/400
FIC PA-2012 Socket7 VIA Apollo VP3 83MHz AMD K6-2/500,
DFI P5BV3+ Socket7 VIA Apollo MVP3 100MHz AMD K6-2/500,
Epox EP-51MVP3E Socket7 VIA Apollo MVP3 100MHz AMD K6-2/500,
Tyan S1590S Socket7 VIA Apollo MVP3 100MHz AMD K6-2/500,
Asus P5A Socket7 ALi Aladdin V 100MHz AMD K6-2/500,
NMC 5VMMX Socket7 VIA Apollo MVP3 100MHz AMD K6-2/500,
Elitegroup P5SS-Me Socket7 SiS 530 133MHz AMD K6-2/500,

The chart shows a range of motherboards based on socket7 which can be used for an AMD CPU upgrade.

Test Setup

Hardware Setup
Processor AMD K6-II+/500
L2-Cache clock 500MHz
Front Side Bus 100MHz
Memory clock 100MHz
Memory Wichmann Workx PC133 SDRAM 128 MB CL2
(max. 1.1 GByte Data Transfer Rate)
Graphics Card Nvidia GeForce
Power Supply 300W
Other components
Motherboard Aopen AX 59 Pro
Network Card 3COM 3C905B-TX
Hard Drive Seagate Barracuda ATA ST320430A
VIA 4 in 1 Driver Version 4.20
GeForce Driver Win98 5.30 (OpenGL and AGP Support)
Software Setup
Windows Version Windows 98 SE, DirectX 7.0a
Quake III Arena Timedemo 1, 640x480x16x85
Expendable Downloadable Demoversion, 640x480x16x85
Unreal Tournament Version 4.05b, Benchmark UTBench
Sysmark 2000 1024x768x16x85


All benchmarks have been obtained with the same hardware configuration. All three CPUs were run at 500MHz (100MHz x 5). We also included the results of an old Intel Pentium 100 to demonstrate the performance improvements over an old system. Although all three CPUs we tested at 500MHz, they also run nicely at 600MHz. Overclocking freaks amongst you will be glad to hear that.

Gaming Performance


The OpenGL gaming benchmark Quake 3 Arena shows that AMD K6-III+/500 is leading the field. Our basic Pentium 100 lies far back in losing position.


Expendable is good for measuring Direct3D performance. Here we see the AMD K6-III+/500 holding a narrow lead in front of the AMD K6-2+/500.

Office Performance


In the application benchmark Sysmark 2000, the K6-III+ shines again with outstanding results. It very clearly dominates over an Intel Celeron of the same speed. We've already published similar results in our last report on Socket7.

MPEG-4 Encoding


The latest item in our benchmark suite is Flask Mpeg which allows conversion of MPEG-2 video to MPEG-4. This benchmark impressively visualizes how closely related encoding speed is to L2 cache size. With its 256KB L2 cache, AMD K6-III+ is an obvious first here. Please note that less is better in this case.

Conclusion: AMD K6-III+/500 is speedy but still unofficial

Thanks to the K6-line of processors, CPU upgrades for older computers based on socket7 are still possible with the K6-2/500. Regrettably, AMD takes a rather inimical position towards end users as far as the 'Plus' versions are concerned.

The powerful AMD K6-III+/500 CPUs with 256KB on-board L2 cache are exclusively sold to computer manufacturers and OEM customers. There's a simple reason behind it: this CPU is intended for Notebook use only. Our test CPU is an exception here.

Compared to both the AMD K6-2/500 and the K6-2+/500 benchmark results proved beyond doubt that AMD K6-III+/500 dominates its competitors. The K6-2+/500 as well as the K6-III+/500 are manufactured in 0.18µm process technology, resulting in a lower power consumption than K6-2 (0.25µm process). Additionally, both CPUs are equipped with PowerNow technology that helps to significantly increase battery life when used in notebooks.

One thing is obvious, though: AMD manufactures their speedy K6-III+/500 in comparatively low numbers. Many users who still use a PC with a Socket7 motherboard will regret this. If you believe the statements from AMD, the supply of socket7 CPUs to important notebook manufacturers (e.g. Hewlett-Packard and Compaq) will still continue for the next few years. So why shouldn't a PC user with a small budget benefit from them as well?


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