buy PC things

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I found a supplier of old hardware, a second hand computer trader. I bought 8 IBM PC base units. One IBM PC pretends to be the Internet, 6 PCs are the the LIC and the final PC acts as the business enterprise.

set your standards

A collection of PCs is unlikely to be homogenous. None of the hardware inside these IBM PCs are made to the same specifications by the same company. This should not matter: they should all work together because they all follow the same design.

A few things do matter. These pointers will save pain later.

LIC topography: buy PC things
PC base units ATX motherboard PCI slots

CPU, disk and memory

A five year old machine is a safe bet. This is the kind of specification I end up with when I buy one of these.

The CPU is 2GHZ speed, with no multiple cores. The disk is about 100GB and connected to the motherboard and power supply using SATA, not the older PATA. The memory is DDR SDRAM 184 pin modules, and something like PC2700 (333-MHz) speed. They are not the older SDR SDRAM modules (PC133, 168 pin, DIMM).

look for ATX motherboards

I only buy PC base units containing an ATX motherboard with one onboard ethernet interface. This limits the age of the PC: this type of computer has only been manufactured this millenium. Older PCs can be a pit of unhappiness, with obscure connectors, weird bugs and a lack of spare parts.

count the PCI slots

The different PCs in the LIC need varying amounts of ethernet interfaces.

Since I buy cheap NICs (Network Interface Cards), each with one ethernet interface and a PCI connector, I need to keep an eye on how many PCI slots are in the PCs I buy. The more NICs a PC must hold, the trickier it is to source.

When buying PCs, either open each box and count the slots or look for PCs like the Dell Optiplex GX260 mini-tower. Tower computers and mini tower computers are the most likely to have 3 slots or more. Small form factor and slimline computers are usually have only between 1 and 3 slots.

count the serial ports

The different PCs in the LIC need varying amounts of serial ports. A serial port is one of the D-sub sockets on the back of a PC which follows the RS232 communication protocol.

  • One external PC (xcl01) needs 1 serial interface to talk to its UPS.
  • The three data network container PCs (ifw01-03) need 2 serial ports. Each one talks to a UPS and an ethernet switch.
  • The other PCs don't need serial ports.

An old PC probably has two serial ports. These might be small 9 pin sockets or big 25 pin sockets. Adapters allow serial cables to be plugged into either.

A new PC may only have one serial port. A PCI card can be installed to add more serial ports.

buy PC things

There are many small businesses that trade old office surplus PCs. £30 gets a good second hand base unit. I found one of these suppliers of old hardware and bought a vanload of stuff.

LIC shopping list: buy PC things
name quantity unit price (£) total price (£)
IBM PC base unit with at least 3 PCI slots
IBM PC base unit with at least 2 PCI slots