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Upgrading an Older PC: Tips, Tricks and Traps Tips and tricks plus how to avoid hidden traps when you upgrade or otherwise rebuild your old system

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Upgrading an Older PC: Tips, Tricks and Traps
Tips and tricks plus how to avoid hidden traps when you upgrade or otherwise rebuild your old system

With the economy softening and job cutbacks in some industries, keeping an older PC running for another year or two might be a more appealing idea now than it was just a few months ago. Although some name-brand PCs can be had for as little as $600 or so, you can usually bring your older PCs up to equal or greater speed for a lot less with a motherboard, CPU and RAM swap.

If your system is more than 5 years old, then you have to be a little more careful about upgrading since you probably would need to replace more than just the motherboard, processor and RAM. If your upgrade also entails replacing the hard drive, optical drive, video card, and power supply, then you might be better off purchasing a new system. On the other hand, you can get motherboards for just over $100 that feature integrated AGP video, Sound, and 10/100 Ethernet. This, plus a 1.2GHz processor for another $100, 256MB of DDR SDRAM for $30, a 30GB-40GB hard drive for about $100, and a 300-watt power supply for about $70, means that you can change your existing system into a real screamer for right around $400.

Before you open up your favorite catalog or browse your favorite hardware vendor's Web site, beware of these potential traps that can turn your upgrade experience into a nightmare:

    - Incompatible case designs
    - Incompatible ATX I/O shield and port layout
    - Incompatible AGP video card slots
    - Shared IRQ conflicts
    - Inadequate system cooling
    - Incompatible memory types
    - Incompatible or inadequate power supplies
    - Existing ISA cards that may not plug into a new motherboard

Incompatible Case Designs

If your system doesn't have an ATX chassis, then stop right there. You'll definitely need to purchase a new ATX chassis and power supply before you can even begin to think about upgrading the motherboard. Most industry standard systems dating from mid-1996 to the present will have an ATX chassis, but check to be certain. You can find the details about ATX at the www.formfactors.org Web site.

If you are planning on upgrading to a Pentium 4 processor, then even if you have an existing ATX chassis you may need something newer. Because of the weight of the active heatsink that the Pentium 4 uses, most Pentium 4 motherboards are designed to use mounting holes in the chassis to support the heatsink. If your case lacks these heatsink support holes, look for a motherboard that includes an underlying support brace that will carry the extra weight of the heatsink. Pentium 4 motherboards that include such a brace will work in any ATX chassis.

Incompatible ATX I/O Shield and Port Layout

There are many variations in the number and arrangement of the rear ports on ATX and Micro-ATX motherboards. While most motherboards include a custom-made rear I/O shield, some expect you to re-use the I/O shield from your old motherboard.

If the new motherboard has additional ports not included on your old motherboard, make sure the new board includes an ATX I/O shield. If you didn't find a compatible I/O shield in the box with the new motherboard, then contact the motherboard vendor for a compatible shield. Centrix International Corp www.centrix-intl.com stocks several replacement models.

Incompatible AGP Video Card Slots

If you have one of the older AGP 2x video cards, make sure you check the AGP voltage rating for your new motherboard. While many motherboards will work with either AGP 2x (3.3 volt) or AGP 4x (1.5 volt) video cards, the new Intel 845 chipset used by many new Pentium 4 motherboards can't work with AGP 2x cards. If you can't switch your card to AGP 4x mode, look for other motherboards that support your card, or get a new AGP 4x card.

Existing ISA cards

Newer motherboards do not include ISA slots as a rule. If your current system uses any ISA slot based cards, they will have to be discarded or replaced with PCI cards. Often you can purchase a new motherboard that has integrated devices that take care of such problems. For example, one system I was upgrading had existing ISA sound and modem cards, as well as a slow PCI based video card. I selected a new motherboard that included built-in 3D AGP video, integrated sound, as well as an integrated 10/100 Ethernet adapter. The user switched from using a dial-up modem to a Cable Modem, which connected directly to the integrated Ethernet. Thus I removed the existing motherboard, video card, sound card, and modem, and installed the new motherboard with no other cards necessary. Careful planning and the use of integrated peripherals to replace older cards can make an upgrade simple and economical.

Inadequate System Cooling

If you move from a sub-1GHz system to one of today's fire-breathing 1.4GHz or faster systems, you'd better make sure your system is ready to move the extra heat away from your CPU. While today's fast CPUs have bigger and more powerful powered heatsinks than slower, older models, the hot air that the heatsink pulls away from the CPU core has to go somewhere. Many older systems lack auxiliary case fans, or might have only a front-mounted fan; in such cases, the hot air from the CPU may not be exhausted properly. Drop one of today's fast processors into a computer with inadequate cooling, and you could cause overheating with potential loss of data and hardware damage.

All of the boxed processors sold by Intel and AMD are designed to cool the processor properly if the internal chassis temperature is maintained at 40 deg. C. (104 deg. F) or less. Some will tolerate internal temperatures as high as 45 deg. C (113 deg. F). You can use a simple digital thermometer such as the "Indoor/Outdoor Thermometer with Large Display" (Catalog #: 63-1009) sold by Radio Shack (currently on sale for $9.99, regularly $14.99). By positioning the outside temperature sensor directly above the CPU fan and then running the cable out the back of the PC, you will be able to read the temperature of the ambient internal chassis air entering the heat sink. If it is over 104 deg. F, you should add additional cooling fans to the chassis.

If you need to add a fan, check the fan connectors on your motherboard. Most recent motherboards support three-prong connectors which provide power, ground, and speed monitoring. Use these fans to enable your system to monitor fan speed (either through BIOS-based hardware monitoring or system management software).

You can add two additional fans in most chassis, one in the back and one in the front. I recommend first adding the rear mounted fan, and it should be installed so that it exhausts air from the chassis. If you need even more cooling, then add a fan to the front of the chassis, this time mounting it so that it blows air INTO the chassis. This will insure that a proper balance of pressure occurs and that the fans don't end up working against each other.

Incompatible Memory Types

Normally you will need to purchase new memory if you are changing your motherboard. It is rare that the memory from your old board will work in something newer. Most older boards used PC-66 or PC-100 SDRAM, while all newer boards use either PC-133 SDRAM, PC-1600 or PC-2100 DDR SDRAM, or PC-800 RDRAM.

If your new board uses any of the newer SDRAM or DDR types, the fortunate thing is that these types of memory are extremely inexpensive. Currently you can get 256MB of SDRAM or even DDR for right around $30. RDRAM on the other hand is 3 to 4 times more expensive, so budget accordingly if you are upgrading to a board that uses RDRAM RIMM modules.

The motherboard chipset determines what type of memory your system will require. If your current system has PC-133 memory, then you can still find motherboards that use that type, and that will make your upgrade about $30 cheaper since you can re-use the memory you already have.

Choose your new motherboard by the chipset it uses, as this will dictate the performance you will get as well as the type of memory you will require. For example, if you want to switch to the Pentium 4 processor and keep your PC133 memory, specify a motherboard based on the Intel 845 chipset. While the 845 is slower than the RDRAM-based Intel 850 or the DDR-based VIA P4X266, it's the only one of the three that supports the PC133 memory you may already have.

If you're in the market for an AMD-based solution that uses PC133 memory, look for VIA Apollo Pro133-series chipsets or the SiS733 from Silicon Integrated Solutions. The Acer Labs ALiMAGiK 1 and SiS735 chipsets can support both DDR and PC133 SDRAM, so check the motherboard specifications carefully.

One thing to consider though, is that the price of PC-2100 DDR SDRAM is so low, and it is up to twice as fast as PC-133 SDRAM, that it usually makes more sense to spend the extra $30 for 256MB of DDR and purchase a board which uses that memory type.

Incompatible or Inadequate Power Supplies

If your system currently has less than a 300-watt power supply, then you may need to upgrade the supply to properly power a newer motherboard with a high-speed processor. In most cases you can probably get away with a 250-watt unit, but anything less than that will seriously compromise the reliability and integrity of your system when it has to run a new board with a fast CPU.

Other power supply issues can trip you up, especially if you have your eye on moving to the Pentium 4. Boards based on the Intel 845 and 850 chipsets both require you to connect a square 4-pin ATX12V connector from your power supply to the motherboard. Most power supplies don't have this connector, so you must either upgrade to a Pentium 4-compatible power supply or buy an adapter designed to make a 300-watt or larger power supply Pentium 4-compatible. Fortunately these adapters are cheap (about $8) and are available from companies like PC Power and Cooling (www.pcpowercooling.com). Note that most motherboards based on the new VIA P4X266 chipset don't require the ATX12V connector.

To adequately power a newer, faster and more power hungry processor, your power supply should match either the ATX 2.01 or preferably the 2.03 specification and output at least 30 amps on the 5-volt line to work properly. Power supplies which are 275 watts or larger will meet this requirement. If you need a higher wattage supply to power your new board and processor, again I recommend PC Power and Cooling, they have some of the best supplies in the business in a range of models and configurations.

Shared IRQ Conflicts

One of the major design features of today's systems is the use of integrated components for sound and networking. As with any I/O device, integrated sound and network ports use IRQs. If you prefer to use separate sound or network cards or plan to add SCSI or other cards to your system, you could have problems if the IRQs routed to the expansion slots are shared with on-board devices or with other slots. Even though PCI slots and Windows 95B and above support shared IRQs, some motherboards don't implement this feature very well.

Check the documentation carefully for your new motherboard before you order it to determine how IRQs are allocated to expansion slots and on-board devices. If a particular slot shares an IRQ with an on-board device or another slot, find out if you can use the slot and the on-board device at the same time, or both slots. If you can't, you may need to look at another, more flexible motherboard. You can view online versions of most motherboard documentation by visiting the motherboard maker's Web site. Make sure you have the latest version of Adobe Acrobat Reader installed so you can view the documentation. Both PCI and AGP slots can have shared-IRQ issues.

One way you can free up some IRQs is to disable ports you don't use. For example, if you don't use serial or parallel-port devices anymore, disable those ports and adjust the system BIOS's Plug-and-Play menu to use IRQs 3, 4, and 7 (used by COM2, COM1, and LPT1 respectively) as PnP-PCI IRQs rather than ISA IRQs. This will enable your BIOS and Microsoft Windows to map newer PCI and on-board devices into those IRQs.


Look carefully at your old system before you decide to buy a replacement motherboard and CPU. Make a bad choice and you could wind up spending a lot more than you planned for additional replacement parts.

Web Resources

For some excellent articles on system thermal design (cooling), visit:

Note that the www.formfactors.org site also has all of the documents describing the ATX form factor including motherboards, chassis, and power supply designs.

PC Power and Cooling offers a variety of ATX and other form factor power supplies and accessories:

You can find out more about VIA chipsets at the VIA web site:

There is an incredible amount of detailed information about Intel chipsets at:

Copyright©2002 Pearson Education. All rights reserved.

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