The Linux system is reasonably easy to please when it comes to the hardware on which it runs. Over the past months I have given out quite a bit of advice to people on choosing a machine for Linux. I thought that it was time to turn these snippets of advice into a proper article - with an eye on producing a low cost but decent machine to run the very low cost Linux software on.
Firstly how much do you think you are going to have to spend to run Linux (assuming you do not have a suitable machine already)? The trite answer is a lot less that you would have to spend to run Windows 95! Seriously though Linux, with the ability to only configure in parts of the operating system that you actually need is "lean and mean"
At the low end of aspirations a 386sx/16 system with a 40MB hard disk and 2MB of memory - the sort of thing that can be bought second hand for a hundred pounds or so - is just capable of running Linux, you might have to get a friend to compile you a minimal kernel though. The two main limiting factors for such a system are slowness and lack of memory (which leads to greater slowness - hard disk speed is a staggering one and a half million times slower than main memory!). However as Linux does have proper support for virtual memory such a lowly machine could be put to useful tasks. Simple text editing and using tools like awk and perl to write programs would certainly be possible. Although I said that swapping to disk is so much slower than main memory on a human time scale a program can be swapped out and in again while you are typing at it without their being any noticeable delay.
Linux, even on a slow machine, is still fully network capable so cheap slow machine could gainfully be employed to act as secondary storage space, or even somewhere to put less speed critical peripherals like printers or low speed modems - possibly even a server to make available World Wide Web pages.
It seems that everybody is in a rush to upgrade their machines to DX/4 and Pentium to face the demands of the latest games and Windows software. There is a glut of perfectly good 486SX and DX processors and mother boards on the market, not to mention complete systems. You should be able to pick up a reasonably modern board with processor for about 50 pounds. Don't be talked much higher than this though the latest 100MHz DX4 motherboards are only around a hundred quid!
No not the number 28 to Clapham! The Bus is the means by which the optional and changeable parts of the computer are connected to the mother board. There are no less than five choices of Bus that you may encounter - I will list them in order of increasing desirability.
While memory prices are in fantasy land what is the budget constrained Linux user to do? There are two factors that must be considered as the market value of memory is likely to bust at any time. Firstly don't hold more memory than you need and secondly plan your memory purchase so that you are not left having to remove and exchange memory to get a larger capacity in future.
A good (but possibly already out of date) tip is to look for mother-boards that have sockets for both 30 pin and 72 pin SIMM memory modules.
As future high capacity memories are likely to be 72 pin as the norm in the future it makes sense to fill your 30 pin SIMM memory banks first - as the 30 pin memory may be out of general production and therefore rare & expensive if you populate 72 pin SIMM slots first. All the above is irrelevant if you can get 72 pin memory much cheaper than 30 pin!
There is a great deal of rubbish spouted about how much memory real operating systems require, Windows95, OS/2 Warp and Linux are all 'speed challenged' with just 4MB. Even if your machine is only a 386 the speed improvement going for 4MB to 8MB is so great that you really cannot value your time at all if you struggle along with 4MB. 8MB is a comfortable amount for 386 and 486dx systems and a more generous 12 or 16MB for 486/66 and 100. If you are investing in a Pentium then 16 or 20MB memory would be an appriopriate complement.
At the other end of the scale are hard disks with the SCSI interface. These are usually only available with capacities of half a Gigabyte up. Coupled with a VESA or PCI SCSI controller they give considerably better performance than even EIDE. SCSI disks have been a bit of a nuisance to support under DOS - they are not part of the original PC-AT scheme of things and so need special BIOS ROMs to boot from and special device driver software. Linux has no prejudice - it has standard device drivers for SCSI just as it has for IDE. A good SCSI card will handle the disks (and CD ROM, Tape drives, etc...) with far less involvement from the CPU than IDE requires. This means that the processor is able to get on with other useful work while data is traveling to and from the disk. For DOS and Windows this was of limited use as what you were doing at the time was probably dependent on the disk transfer finishing before continuing anyway. However Linux and other real multi-tasking systems will find that the amount of extra performance difference between a SCSI and IDE equipped machine to be definitely worth the extra cost of SCSI controllers and peripherals. SCSI is the system used by most of the BIG Unix mini-computers such as HP-9000 and IBM RS-6000.
A word of warning about buying second hand SCSI disks. They are used by the truck load in the big systems. A hard disk has a finite life, and unlike a car there is no mileometer to check. If you are offered SCSI drives on the cheap bear in mind that their previous life might have been one of hard work inside a big multi-user system rather than the comparatively leasurley life that most PC hard disks get!
A disk that is a few years old may keep working for you for a good few years more. On the other hand the disk may have been removed from its home with only a few months to go before the expected end of its life. Such planned swap out of hard disks makes a lot of sense to operators of big systems. Arranged downtime and no data loss is much preferable to a disk crash and lost data!
Never, ever pay good money for a disk that whines - it is a sign that the disk bearings are beginning to wear. Such a disk, if you can put up with the noise, may still have several months of useful life left, but it may fail at any time. So be careful! One possible use could be to act as a cache for your Linux CD-ROM. When the disk does finally fail you will have a minor inconvenience - but maybe a system crash but should have not lost any data.
If you are serious about using Linux as a real X Windows Workstation then 16MB of RAM is an absolute minimum. If you want to run the same sort of packages that modern Unix Workstations can you will have to match their memory capacities - there is no shortcut or bodge. However even with the current high price of memory a Linux Pentium PC with 64MB of memory is only the fraction of the cost of a dedicated Workstation and capable of doing most of the same things.
The other part of the equation for a serious Workstation is the video system. Forget ISA bus VGA card and 14" screen! What you need to give X a chance to shine is a good VESA or PCI video card with at least a 17" Monitor. If you are going to be using X Windows on more than a casual basis it is well worth the investment on a big, clear screen. Good 17" monitors only cost around 400 pounds nowadays - that's about 250 more than a cheap 14" one.
To this I would add 64MB of memory - as that is what serious multi-user Unix boxes seem to start at these days and an accelerated video card with 4MB of video memory and a 21" monitor.
The cost of all this? I've not bothered to add it up but probably about the same as a decent car. In contrast really aggressive spec Unix Workstations have been into the hundreds of thousands of pounds!
PCI Bus mother board again. The price premium is so small now that it is worth paying for the ability to choose ALL PCI expansion cards. Even if you mother board has ISA bus slots try to avoid using them if you want real performance.
Processor. At the moment (although things may have changed by the time you read this) the AMD DX/4 chip offers by far the best price/performance ratio. PCI mother boards complete with DX/4 processor can be had for around a hundred and fifty pounds. A Pentium 100 board/processor combination is at present about 200 more than this. So for 200 you get about double an already very quick performance. BUT if you are on a budget 200 pounds worth of memory will probably gain you more real world performance than uprating the processor. A DX/4 seems to have more than enough clout to play the latest full motion video games so don't let your judgement be clouded by Pentium envy.
With the money saved from having a DX/4 instead of a Pentium get a full 16MB of memory. If you can afford it get even more - Linux will always make best use of the memory it has, if nothing else it will mean more data from the hard disk can be cached. Please bear in mind that memory is very expensive at the moment and the price is bound to come down a lot sooner or later. However why waste time with a machine that is only working at a tiny fraction of its possible speed because you have been memory mean? Machines that serve hundreds of users have big memories rather than very fast processors.
You will find a 17" monitor is probably big enough for your needs. Do try and get a video card with at least 2MB of video memory on it though - otherwise you will be limited to 1024x768 pixel resolution rather than the more Workstation like 1280x1024.
Lastly Hard disk space. Go for SCSI if you can because of its much better performance under multi-tasking conditions. However 1GB EIDE drives for about £150 are hard to resist! Why not go for both? A 500MB or so SCSI for the core of critical files and an EIDE or two for bulk but less heavily used storage?