If i were going to buy a cheap, upgradable server...
-Antec has some good, relatively cheap, cases with 120mm fans. Expect to pay around 50-70 for them.
-If you want expandability, you'll want to go with a newer mobo. Expect to pay around $100-200 for a 939 board.
-I'd pick up a 3000+ A64, since it's pretty much the low end of the cpu spectrum of 64s, with the exception of the 2800..but really outshines it for a small difference in cost. $140-155
-if you want to get a quieter heatsink, look at the lower of those cpu costs; but include an extra $30-40 for a quiet heatsink
-I'd pick up a gig of ram, it's cheap...$130 geil 2.5, could go cheaper and get $100 kingmax 3.0.
-i'd pick up a belkin dual switch $30; so you can hit a button and go back and forth between two computers; (cuts cost of buying a second monitor keyboard and mouse)
-if this isn't a gaming machine, buy the cheapest gpu you can get your hands on ($20-40 new)...just check to make sure it A. works with the mobo you get (pci-e vs agp) and B. has drivers in the flavor of linux you're using.
-hd's $60-100, i'd recommend 2 in raid 1 (mirroring); it's not terribly hard at all to set up in linux as you're building your system (or you could get a hardware solution with your mobo)...premium names are western digital and seagate...be sure to get liquid ball bearings or the equivalent, makes a difference audibly (for instance: 36gb wd raptor vs 72gb wd raptor, the 72 has liquid ball bearings and isn't nearly as loud); there are sites that have tested how many decibels several hds have made if you're willing to search them out...perhaps someone else could help with a site...
-sound...onboard or nothing at all...
-ethernet...onboard will be fine...most new mobos come with ethernet onboard...if you get a gf4 mobo, go with nvidia's ethernet over broadcom's;
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If you wanted to go real cheap...just pick up a hella cheap dell small buisness server. $200-400
-Dell SC240 currently $240.
*no OS, Celeron cpu, made to work with linux or win server 03, doesn't have drivers for the intel chipset that work well for XP and 2000 (from personal experience...officially not supported by intel);
-Belkin 2-port switch $30
-toss the 128mb ecc to the curb...buy 1gb 3200 same as above (that way if you upgrade the cpu at a later date on a 800mhz bus you will be ok...i think this board is capable of up to a p4 3.4);
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Prices taken from New Egg, Dell, and zipzoomfly.
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Eyes tired of reading yet?
Good Luck
Current machines running F@H:
Athlons: [64 3500+][64 3000+][2500+][2000+][1.3x1][366]
Pentiums: [X 3.0][P4 2.4x5][P4 1.4]
It's not worth saying unless it takes a really long time to say!