On the conservative end of the upgrade justification distribution curve, heres an outlook that might produce a few yuks and possibly be informative.
I'm so bloody Scotch that I only do significant upgrades about every 5 years. When I do upgrade I mostly use pre-owned components that are already 1-2 years old but have a track record of being reliable. Since computer gear depreciates at about 40-45% per year (my observation over several years), this saves quite a bit of money. Im probably compulsive about that.
My current main rig is a Socket 754 Sempron 2500+, E6 core, 1.4GHz stock overclocked to 1.8 or 2.2GHz (at default Vcore), depending on how I feel on any given day. Motherboard is a Chaintech VNF3-250 (bought used here on the AnandTech forums for 25 bucks) that is still fully functional. Early on I installed a 30MM fan on its south bridge heatsink and I think that minor mod has extended the boards longevity. My case is a $23 (delivered) ATX overclocking case with provisions for 13 case fans (!) that I bought in 2001. I love that case and may instruct my heirs to include it in my grave (thought the same way about my 83 Toyota Corolla but sold it last year to a needy neighbor). Hard drive is a five-year old 80GB Seagate ST380013A (7200.7 series) that still passes Seagates quick self test with flying colors (a 92MM intake fan is blowing air above and below it installed the fan simultaneously with the drive). Memory is 1GB of PC3200 (original DDR, 184 pin), a relatively late upgrade from 512MB precipitated by going virtual during eBay searches that produced tens of thousands of hits.
And Im still running Win2K (behind a routers firewall and using the last free version of ZoneAlarm that runs on Win2K).
Do I hear several gasps, gawds and/or expletives?
Thankfully the latest versions of Avast still run on Win2K. WinXP is OK but I just have no need for it. Vista (yuk) and Win 7 certainly arent necessary for what I use my PC for. And since, as a retired software developer, I remember the days of stuffing code into as little as 32K of memory (yes, thats K as in Kilobyte, 1024 bytes), breaking programs via subroutines into overlay segments (an approach to memory management used prior to the advent of Virtual Memory), I dont have much respect for Operating Systems that eat 500MB+ idle at the desktop.
I just use my system to surf the net (Cox Preferred service) and very occasionally play the original version of Far Cry (started using an AGP FX 5200 graphics card [yes, yuk but suffices] about 3 years ago after my heatsink mod covering several chips on my Radeon 9700 fell off the chips it was supposed to cool and I was too lazy to fix it).
BUT (trumpet fanfare) it is time to upgrade. Over 5 years have passed since my last major upgrade. Between ZoneAlarm being a processor resource hog and the processor demands contributed by Avast and all the scripts that one encounters on web pages, Im seeing my CPU utilization hit 100%. In early morning tests (periods of less bandwidth competition from other Internet traffic, which tends to make bandwidth testing more meaningful), when I turn off ZoneAlarm my Internet bandwidth increases substantially. My tolerance for anything less than maximum Internet bandwidth is not high, especially given that Im paying for that bandwidth.
So Ill probably buy an E2000, E3000, or E5000 series processor (likely one of the 45nm jobbies), clock it to between 3 and 3.3GHz on a (used, of course) Gigabyte GA-G31M-ES2L (V1.1) I have as a spare board for a customer (his build warranty is nearing its end), add a 7600GT and get on down the pike, still running Win2K with the option to migrate to Linux (the Gigabyte board is very amenable to Linux). And do the upgrade for a hundred bucks or so.
Keep in mind that lack of money is by no means an issue here.
Its my attitude
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