When I put the system together (actually I put two together), I wasn't planning to do the webserver thang and had never heard of the ACS. One system was intended as playground for me while I checked out some new technologies and brought some skills up to date. I wanted to check out threading on a system that truly had two processors. That's one reason for the dual processors. (And then I stumbled into a seminar sponsored by the j school, held at the b school, led by a familiar name from my LISP days....(the j school has the best seminars, usually free, and often with food!))
Another reason was that this dual processor Supermicro motherboard was only $30.00 more than the equivalent single processor Supermicro motherboard. At the time, it seemed that putting a single processor into a dual processor board (that's the webserver configuration) was a cheap investment that yielded a pretty reasonable future performance upgrade extending the longevity of motherboard and system. That may or may not have been valid. At the time I thought it was valid, but since then I've heard several times that for many of these dual processor systems, you really need to get two processors made in the same batch, or else you can run into timing issues. So you can't just get another processor of the same speed as the first processor. That seems dubious to me, but has just the ring to it that means it might be true. If it is, then the future upgrade has to be two new processors, not just one. So is that truth or myth? Regardless, if the current difference in price between single and dual processor board is not much, I do think that getting a dual processor board and one processor is a good choice.
The third reason I had for going for a dual processor system was that two 500Mhz processors were more or less the same price as one 850 Mhz processor and theoretically could offer better performance under the right circumstances. I recall the 850Mhz was the top of the line then or very close to it, and I prefer to buy many things at a reasonable bang per buck part of the curve -- that keeps me from being disappointed a week after buying the 3Ghz machine when the 3.05Ghz machine comes out. (Offline, ask me how to buy a used car in terms of most bang for least buck.) I don't believe AMD was anywhere near competitive in terms of top end performance back then. That's not quite true. I spent a week with a dual processor AMD motherboard from ABIT, it was the first of its kind, and I believe it was an unauthorized, unstable hack that could be made work with enough spit. I didn't have enough spit so I refunded the thing and went with the Supermicro.
Coda: yesterday for $240 I ordered two 850Mhz processors, and wanting to be able to run VMware decently at the same time I am running Oracle and potentially NetBeans, I picked up a gig of registered ECC SDRAM for $200. Why registered? The board requires registered mem if you want to put a gig in. Okay, the joke is on me, of the three pieces of software I just mentioned (Virtualizer, RDBMS, Java IDE), which has the largest amount of memory suggested/required for decent performance. Yeah, the Java IDE which I recall suggests 512M, but many folks say it doesn't get honest until you have 768M. So for $450 I should have reasonable performance and I don't have to figure out how to recycle the old machine. SCSI drives may be in the future, but being a bit of a tightwad, I may opt for the latest in IDE controller and drive technology. (I have two or three 1G SCSI drives that well, I could buy a car for what those things cost me then.)
