Socket 5 - Tuning Old PC Systems
Редакция THG,  12 февраля 2001

Tuning instead of disposing: PCs with Socket 5


The most important news first. Old computers that are already getting a bit long in the tooth can be given a helping hand at relatively little expense. Increasing overall performance by 100 percent and more is no rarity! Many a PC system, long since fallen into oblivion and mouldering in the seclusion of a basement, can shine once more. In another scenario, many companies still have numerous old PCs that perform their work on the good old DOS operating system. In most cases, the existing hardware is even sufficient for their specific area of use. Nevertheless, if the equipment is to be upgraded to the graphically attractive and modern Windows 98 operating system, the PC system lacks the necessary performance to do this.

Both private users and small to medium-sized companies find themselves faced with this difficult decision: what does one do with computer hardware that was purchased a few years ago and is now unable to work with modern operating systems а la Windows 98 or Windows NT 4.0 as well as the appropriate application software? In this case, there are only two possibilities. Either new PCs have to be purchased or the old PCs are upgraded. From this it becomes clear that the latter is unquestionably the more cost efficient and less time-consuming method, although a decision has to be made on a case by case basis for each PC system. We have closely examined numerous older PCs and come to the conclusion that most systems up to six years old are suitable for an upgrade.

PC System

Too good to throw away: this PC system from 1995 can be upgraded at low cost.

Tuning instead of disposing: PCs with Socket 5, Continued

To give you an example, we managed to equip a computer from 1995, fitted with a Pentium 75 on a socket 5 AT motherboard (Intel's 430FX chipset), with a 400MHz processor and additional main memory, with the following result: the overall system performance boosted up to 150 percent simply by increasing the CPU clock from 75MHz to 400MHz (550 percent!) and the memory clock!

Asus P55TP4XE

Upgrade basis: our PC system is based on the Asus P55TP4XE.


Upgrade basis: motherboards with Socket 5 were used in PC systems between 1995 and 1996.

Pentium 90

Our PC still has an old Pentium 90 in Socket 5.

Upgrade the old or purchase the new?

Owners of aging PC systems have a difficult decision to make, either they part with their old computer and purchase a new PC or they upgrade the old-timer step by step. However, at this point we want to make one thing clear: anyone who expects maximum performance and wants to use the system for modern 3D games or other performance-hungry applications, such as MPEG-4 encoding, should go out and buy a new PC straight away. Fore more abitious users, our Do-it-yourself PC article lists suitable components and gives step-by-step assembly instructions. Take a closer look at a PC system from 1995. The case and the motherboard still follow the outmoded Baby AT format. Components of this kind are still available on the market, but only in isolated cases, so upgrading the mainboard involves the additional purchase of a new power supply along with the case. A new processor and new main memory (DIMM modules instead of the old SIMM modules) add to the costs. Besides the financial expense, the time it takes to assemble the components is also significant. A different picture emerges if a modern mainboard is available in the Baby AT form factor with Socket 7 and direct AMD K6-2 support. In this case, only the processor, the motherboard and maybe the memory have to be upgraded.

CPU Upgrade: voltage converter for Socket 5

Up to the end of 1995, mainboards with Socket 5 were used in most PC systems. An AMD K6-2 or AMD K6-III cannot be directly installed in such computers. The reason for this is that there is only a simple voltage converter on the motherboard, which does not support any split voltages required for the new AMD processors. Generally speaking, the voltage converter on old boards only makes a voltage of 3.3 volts or 3.5 volts available. All fast AMD processors in the K6-2 series (and K6-III series) must have a core voltage of 2.2 volts max. and an I/O voltage of 3.3 volts. In order to use the AMD processors in the Socket 5 motherboards, an upgrade socket has to be used with an integrated voltage converter. Powerleap markets suitable models. Anyone who wants to buy the upgrade socket and the AMD-CPU separately has to rely on Internet mail-order suppliers.


Once the old processor has been removed, the upgrade socket (with voltage converter) can be inserted into Socket 5.


Afterwards, the AMD K6-2 is plugged into the upgrade socket. Watch out: the upgrade socket has no lever arrest!

Step by step: installation of the upgrade socket

It is very easy to replace the old processor, as long as you use an upgrade socket along with the new AMD K6-2 CPU. The two pictures above show the first steps involved. Once the upgrade socket has been inserted along with the processor, the special heat sink can be secured.


This is what the upgrade socket looks like with the CPU and heat sink. Important: the additional voltage supply of the converter on the upgrade socket must be monitored!

Socket 5

The upgrade socket from PowerLeap is compatible with most Socket 5 and Socket 7 motherboards.

The voltage for the CPU core as well as the clock multiplier can be adjusted on the upgrade socket.

Socket 5

Voltages and timing multipliers are finely adjusted by the DIL switch on the upgrade socket.

Technology: processor bus clock, multiplier and CPU core voltage

Here's another look at the DIL switch on the upgrade socket.

We restrict ourselves in the following description to mainboards with Socket 5, which are equipped with an Intel 430FX chipset. As the CPU clock (processor core clock) is derived from the processor bus clock and the clock multiplier, the highest possible clock rate should be chosen in principle for the upgrade. Otherwise such a high clock frequency is not achieved and performance is wasted. Here is an example to illustrate this: The Asus P55TP4XE that we tested offers a maximum processor bus clock of 66MHz. As a rule, the board supports a maximum clock multiplier of 3.

Socket 5 - Multiplier and Clock CPU clock
3,0 x 66MHz 200MHz
2,5 x 66MHz 166MHz (Pentium 166)
2,0 x 66MHz 133MHz (Pentium 133)
1,5 x 66MHz 100MHz (Pentium 100)
1,5 x 60MHz 90MHz (Pentium 90)
1,5 x 50MHz 75MHz (Pentium 75)
Upgrade Adapter - Multiplier and Clock CPU clock
6,0 x 66MHz 400MHz (AMD K6-2/400)
5,5 x 66MHz 366MHz (AMD K6-2/366)
5,0 x 66MHz 333MHz (AMD K6-2/333)
4,5 x 66MHz 300MHz (AMD K6-2/300)

Comparison of the clock adjustments from the factory and with that of the CPU upgrade socket.

Technology: processor bus clock, multiplier and CPU core voltage, Continued

The table below compares the different CPU platforms. The AMD K6-2 can also be used in some Socket 7 boards without an upgrade socket. The only prerequisite is split voltage.

Processor Platform Core Voltage
Pentium 75 Socket 5 3.3 Volt (no split voltage)
Pentium 90 Socket 5 3.3 Volt (no split voltage)
Pentium 100 Socket 5 3.5 Volt (no split voltage)
Pentium 133 Socket 5 3.3 Volt (no split voltage)
Pentium 166 Socket 5 3.3 Volt (no split voltage)
AMD K6-2/400 Socket 7 2.2 Volt (Core and I/O voltage split)
AMD K6-2+/500 Socket 7 2.0 Volt (Core and I/O voltage split)
AMD K6-III/450 Socket 7 2.2 Volt (Core and I/O voltage split)
AMD K6-III+/450 Socket 7 1.9 Volt (Core and I/O voltage split)

Once ago 200MHz (66MHz x 3 = 200MHz) used to be the limit! However, by using the upgrade socket from PowerLeap, multipliers between x1.5 and x6 are freely available in half steps, thanks to the integrated engineering logic. All processors from the K6-2 series upwards interpret a clock multiplier of x1.5 as x6.

It is possible to insert the processor in boards with dual voltage (CPU Core and I/O voltage) without the need for an upgrade socket, but most of the old boards restrict the selection range of the clock multiplier. Therefore it is always wise to use the upgrade socket. It enables you to adjust the clock multiplier as well as the core voltage via special dipswitches. The voltage is adjustable in small increments within the range of 1.8 volts to 3.5 volts. Between 1.8 volts and 2.1 volts, it is even variable in 0.05-volt steps.

Memory upgrade: SIMM memory modules are scarce!


The SIMM memory modules have become very scarce and are only available from selected specialist dealers. Nevertheless, a memory upgrade is worth it. We have extended our system from 16 MB to 48 MB.

Cache Memory

In the case of boards with a 430FX chipset, the L2 cache was on the motherboard. These modules were very slow by today's standards.


The L2 cache could be extended in the form of a COAST module (COAST = cache on a stick).

Besides exchanging the processor, upgrading the main memory also guarantees additional performance. Keep in mind, though, that the so-called SIMM modules are already very scarce on the market, so that purchasing the modules can cause slight difficulties. Our test system was equipped from the factory with a total of 16 MB main memory and still had two free SIMM slots in reserve. With the aid of two more 16-MB modules we equipped the computer with a total of 48 MB memory.

Upgrade 1: Suitable PC systems

The table below shows a few PC systems that are suitable for an upgrade with an upgrade socket or the use of an AMD K6-2 processor.

Manufacturer PC System CPU Platform
Compaq Deskpro XL 575 Socket 5
Compaq Deskpro XL 590 Socket 5
Compaq Presario 3000er series Socket 5 or Socket 7
Compaq Presario 4000er series Socket 5 or Socket 7
Dell Dimension XPS 75 bis 166 Socket 5
Gateway P5-75 Socket 5
Gateway P5-90 Socket 5
Gateway P5-100 Socket 5
Gateway P5-120 Socket 5
Hewlett Packard Vectra VL 5/75 Socket 5
Hewlett Packard Vectra VL 5/90 Socket 5
Hewlett Packard Vectra VL 5/100 Socket 5
IBM Aptiva 2100er series Socket 5
IBM PS/1 series Socket 5 or Socket 7
IBM PC330, PC340, PC350 Socket 5 or Socket 7
Siemens Scenic 75 to 166 Socket 5

This table shows a selection of PC systems that are suitable for an upgrade with an upgrade socket and a fast AMD K6-2 processor.

Upgrade 2: Suitable motherboards

The table below clarifies to what extent motherboards with Socket 5 and Socket 7 are suitable for an upgrade based on examples.

Manufacturer Motherboard Chipset Platform Release Dual voltage for AMD K6-2
Abit PR5 Intel 430VX Socket 7 1996 no, socket adapter neccessary
Abit AR5 Intel 430VX Socket 7 1996 no, socket adapter neccessary
Abit PR5 R2 Intel 430VX Socket 7 1996 no, socket adapter neccessary
Aopen AP5V Intel 430VX Socket 7 1996 no, socket adapter neccessary
Asus P55TP4XE Intel 430FX Socket 5 1995 no, socket adapter neccessary
Biostar 8500TVG Intel 430VX Socket 7 1996 no, socket adapter neccessary
FIC PA-2006 Intel 430VX Socket 7 1997 yes
Gigabyte GA-586ATM Intel 430FX Socket 5 1995 no, socket adapter neccessary
Gigabyte GA-586ATE Intel 430FX Socket 5 1995 no, socket adapter neccessary
Tyan Tomcat I Intel 430FX Socket 5 1995 no, socket adapter neccessary

This table shows a selection of motherboards that are suitable for an upgrade with an upgrade socket and a fast AMD K6-2 processor.

Test Setup

Processors Intel Pentium 75MHz
AMD K6-2/400
L2 Cache Clock 66 MHz
System Bus Clock 50 or 66MHz
Memory Clock 66MHz
Memory IBM SIMM 48 MB 16 ns
Motherboards ASUS P55TP4XE, Rev. 2.1
Bios 14/02/1997
Graphics Card NVIDIA Riva 128, PCI
Win98 default drivers
Sound Creative Soundblaster 64
Network 3COM 3C905B-TX, 100MBit/s
Hard Disk Maxtor 850MB
Software & Settings
OS Version Windows 98 SE, Service Pack 1
Screen Resolution 1024 x 768 x 16 x 85
SYSmark 2000 Version 1.0, Patch 4
Quake III Arena Timedemo 1

Performance comparison: Basic model vs. tuning

To measure performance, we used the Sysmark 2000 application benchmark from BAPCo as well as the Timedemo1 from the well-known Quake III Arena games benchmark. Both test procedures clearly prove that the total system performance increases considerably by using the fast AMD-CPU in conjunction with the memory upgrade. Originally the processor bus clock of a Pentium 75 is 50MHz. It is then increased to 66MHz for an AMD K6-2/400. This influences the overall performance significantly. The L2 cache and the memory are also automatically clocked at a faster rate by increasing the processor bus clock. It's just rather annoying that the processor bus clock for the Intel 430FX chipset can only be adjusted to 66MHz. Further increase of the processor bus clock to 75MHz or even 83MHz (as is offered by some boards with a 430HX chipset) would facilitate a processor core clock of 450MHz or 500MHz! And all this on a platform that is more than six years old.

BAPBCo Sysmark 2000

Quake III Arena Timedemo 1

Conclusion: Powerful performance injection for Socket 5 boards

Our tests have shown that the efficiency of a Pentium 75 Socket 5 system that is more than six years old can be greatly improved by means of selective tuning. Only an upgrade socket from Socket 5 to Socket 7 is necessary. We used an adapter from Powerleap. As a result, a processor bus clock restricted to 66MHz offers a maximum achievable CPU clock rate of 400MHz (66MHz x 6 = 400MHz). This clock increase is still quite substantial, especially when you consider that a Pentium 75 was used originally. The increase in frequency turns out to be more advantageous with some Socket 7 boards based on Intel's 430HX chipset. Some of these offer a processor bus clock of up to 83MHz, to reach a processor core clock of up to 500MHz.

Still every user should think carefully about planning an upgrade. Unfortunately it is still impossible to tune one of those oldies as much that it would achieve the performance of today's computers. The actual purpose should be to optimize the old hardware so that it runs a modern operating system as e.g. Windows 98. The benchmark results demonstrate very clearly that our PC increased its performance tremendously with the AMD K6-2/400. The Sysmark2000 benchmark proved it. Similarly, with Quake III Arena we achieved almost twice the frame rate. Ultimately though, the optimized system is way behind the results of modern boards with a Socket 370 or Socket 462.

The table below once again summarizes the costs for an upgrade. Note that we've also marked the mobile K6 versions with a "+". If you can't get hold of an K6-2/III 400MHz anymore, you have to resort to an 450 or even 500MHz version. Please don't forget that these models will still be limited to 400MHz, because the old boards are not able to supply the required processor bus clock of 100 MHz.

Upgrade Costs Est. Price
Processor, AMD K6-2/400 $35
Processor, AMD K6-2+/500 * $75
Processor, AMD K6-III+/450 * $69
PowerLeap PL-ProMMX w/o CPU $50
PowerLeap PL-K6-III with 400MHz CPU $199
32 MB EDO memory (60 ns, SIMM) $30

* limited to 6x66MHz = 400MHz

Costs for the simple upgrade of an old Socket 5 system.


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