Select used computer
Home ] Up ] Ten ways to protect yourself on Internet ] Speed of computer ] Server ] Upgrading computer ] [ Select used computer ] FAQ on CPU ]


How to select an old computer?

This document was prepared in Jan1995 to advice people on buying new computers. It is very interesting to look back because it is almost history. It may be useful for people looking for an used computer.

1. New products keep on emerging, therefore, prices keep on going down by the day because of obsolescence. Distributors purchased pre-assembled products from the factory, and by the time they could display their merchandise is no longer current on price and performance. To keep ahead of time, and price economy, custom order a computer is a wise choice.

2. Do not buy the best computer for business and give your old computer to the kids to play. You should do the reverse way, because graphics and games require a much faster high performance computer than a business computer.

3. Most current CPUs are Pentium 100, 90, 75, 66, and 60. 486s will be phased out in the near future. You need minimum of 4 M byte of memory to run Windows programs. 16 M byte with parity check is more preferable. Hard disk prices are keep on falling, 540K is already standard, 730K is deluxe. 1G will be standard in the near future. Double speed CD-ROM is current, but it will be replaced by quad speed in the very near future.

4. On buying a slow computer with minimum memory, and with a small hard disk. It may cause trouble in your future upgrade. A slow computer may not be able to handle your job in the future. It may turn out not worth to spend any more money with it. If you expect to upgrade your memory in the future, make sure you get the minimum number of strip of memory modules with the maximum amount of memory. Otherwise, you may have to discard some of your old memory because of no room to install new modules. You may also have no room to install extra hard disk if your case is too small.

5. Do not compare prices base on the data supplied by your dealer. These data are usually looks attractive and are full of redundancy. You have to look more deeply into the specifications. Such as the speed and manufacturer of the CPU  The mother board and bus system, cache memory, ram speed, parity checks, hard disk size, access time, monitor resolutions, fax modem data speed, CD-ROM speed, sound card bits, speaker poWer amplifier ratings, etc. Two computers with identical list of components could have big different in cost price because of supplier could replace them with some inferior components.

6. Name brand computers do not necessary mean better quality. In fact, they are not necessary manufactured by themselves. Their products are usually OEM (Original Equipment Manufacturer.) That is, they order the product from some cheaper manufacturer to manufacture under their brandname.

7. If you have the need to buy a computer, then buy it without regret. In very short time, you will find you are paying too much for it. If you want to wait for the price drop, then, you will find your waiting is for ever. When you found the price is right, you will also found it is no longer the thing people deserve.

8. Hi-Tech could help you to select the best and affordable computer. We are very glad to explain to you at no charge. For your price and performance benefits, We do not stock any item. Everything is custom for you. Please make appointment with us if you have decided to buy.


Selection tips:

1. CPU             486 and 586 are two main types of Central Processing Unit available nowadays. They can have built in co-processor or without co-processor. Co-processor is an additional special computer that performs mathematics. All graphics and mouse movement will require mathematics to be performed, therefore you will need co-processor even if you do not calculate. CPU can operate at different speed. The communication bus could also operate at loWer speed than the CPU. For example. A model 486SX2-50 is a CPU without co-processor, operating at 50 M Hz with a loWer  bus speed. Pentium 100 is a CPU of 100 M Hz with built in co-processor operating at loWer bus speed. For Pentium you are recommended to get 75 or 100 becuse 75 is at loWer price and can be upgradable while 60, 66 can not.

2. Bus              PCI, VLB, ISA are three main type of bus systems. PCI and VLB are 32 bit high speed bus systems. ISA are classic 16 bit system. Most motherboard will include ISA because there are still some slow speed devices such as modem will require them. On selecting a mother board, you can specify the chip manufacturer.

3. Cache            CPU does not communicate directly with memory because of different level of speed. Therefore, they require some high speed memory as scatchpad. With todays standard, 128K is minimum, 256K is average, 512K and 1 M are options.

4. Memory            You do not need much memory if you run only DOS programs. Most DOS programs can access up to 640K memories only. If they run higher than 640K, they will require special system configurations to operate the expanded or extended memories. Otherwise, you may still have running out of memories even you actually have plenty of available memories. Windows programs require lot of memories. 4 M Byte is minimum, 8, 16 are recommended.  Memories constitutes nearly 1/3 cost of the whole computer. Motherboard can accommodate certain number of strips of memories. Memory strip manufactured in different memory configurations. Therefore, if you purchase a computer, make sure they are easily upgradable. Otherwise, you may have to discard some or even all of you old strips. Lot of brandname computers do not use standard configurations, therefore, you will expect to pay much more money.

                        Parity check is a feature to cross checking the error during program execution. Memory with parity check feature has 9 bit instead of 8 bit. Low end product do not have parity check.

5. Hard disk            200M hard disks are considered small in nowadays standard. 540M is recommended. 1 G will take over soon. IDE and SCSI are two common interfaces. They are equally good and reliable. IDE is more common. SCSI is faster. Modern hard disk access times are usually 10-20 m sec. Hard disk controllers can have 8, 16, or 32 bit configurations. 16 bit access are normally used even if you have a 32 bit bus, unless you have configurated it with 32 bit data access. Therefore, you must specify your supplier to configure them or you are wasting money to purchase such an advanced system.

6. Floppy            One 1.44 M floppy will be enough.

7. Keyboard, mouse  101 Enhanced keyboard are standard. Mouse are also very reliable in nowadays. People are more concerned on fashions and cosmatics.

8. Monitors            Super VGA, interlaced, non-interlaced, refresh rate are not too important to be considered. A very low priced monitor can still have very high performance in nowadays technology. Do not waste money on feature selections, they may turned ou to be the same product. You must get a high resolution CRT for good view. A 0.28  CRT is considered good, 0.31 is fair, 0.39 is poor.

9. VGA controller            VGA control card can cause lots of program conflict if it is not properly selected, matched, and configured. Improper selection can have screeen interference, program hang up, lost of hard disk cluster etc.

10. CD-Rom            CD-Rom is a very slow device. They are still under improvement. Quad speed will replace double speed soon.

11. Sound card            You must specify 16 bit when you purchase them. Low end product could substitute with 8 bit product.

12. Speaker            You can get speaker only, speaker with booster, speaker with poWer amplifier, or just a cable to hook up to you stereo system.

13. Fax Modem            Fax modem speed are keep on increasing. It is not necessary for you to operate at maximum speed just because you have a fast modem because you speed is actually determined by you line quality, and your  host. Nowadays, modem can be operated as terminal, internet, Fax machine, Fax on demand, voice mail, ansWering machine, and etc. at surprisingly low price.

14. Network                Network is useful to share resources betWeen computers. It is very useful if you have two or more computers. Accounting programs must operate in a network environment if you have two or more terminal. With the advance of technology, networking is no longer limited to large coporations. For as low as $200. You can set up a very high performace network.

15. CPU fan                 High speed CPU requies extra cooling to extend its life and to reduce computation error.

16. Case                      You can select desk top model for good looking or toWer model for space saving. Mini size with two expansion slot is already adquate for most purpose. Mid toWer size will alow more room for future expansion. Full size is too big for home use.

17. Green feature Green feature is a energy saving system which can loWer your CPU speed, standby, suspend you computer , monitor, hard disk , etc on idling. Green feature could cause conflict on certain program. It may not work as desired.


Hi-Tech E Commerce
5143 Tomken Road, Mississauga, Ontario L4W 1P1, Canada.
Tel: 905-625-9261