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Thoughts on community computer labs

Hi Kenneth -

Just some random thoughts on a computer lab project...

I didn't have any "boxes" donated. I paid $11 ea. for compact "desktop" HP systems (dc7900), $21 ea. for larger "minitower" HP 8000 Elite.

The compact models are minimally adequate, however the mini-towers have more expansion capabilty, larger power supplies and better cooling. For example, if you upgrade a compact system to a four-core CPU, you might need to use an expensive low-power CPU to avoid power or cooling issues. This alone wipes out the initial price advantage. Compact systems are also limited to "half-height" video cards, which are less capable demanding applications. Although the compacts are cheaper and more plentiful used, careful consideration must be given to whether they will be adequate in use. Bottom line: if compact systems are donated, use them. However it's probably better not to buy them. Used mini-towers are probably well worth an extra $10-15.

I also paid $33 each for larger HP xw6600 "workstations" These have dual CPUs with four cores each, Up to 32GB of RAM, more than twice as many cooling fans and 650 watt power supples. This would be overkill for most purposes, however the additional cores are a bonus if you are "rendering" architecture drawings or video, i.e. synthesizing photo-realistic images. Rendering can take hours to several days. Doubling the number of cores halves the time. Workstations are also better choices for fileservers.

I had to drive out to San Dimas and San Bernardino for all these deals on "boxes". Two of these were online auctions. Other parts came from around L.A. county and Orange County as far down as Irvine. Fortunately I own a pickup truck.

The "boxes" I bought all happened to be HP brand, however I was also prepared to buy Dell or Lenovo/IBM. I stick with model lines intended for business use (e.g. Dell Optiplex), since they are designed for 24/7 reliability plus easy setup and maintenance. Large firms and government offices buy these by the truckload and replace them every few years, so they become available in quantity at favorable prices. If you're setting up a roomful, it's good to purchase lots and avoid chasing around after individual items, even at low prices.

Disposing of the older equipment probably costs businesses at least as much as they get back from the sales. If businesses are taxed, you could probably offer attractive tax deductions for donations instead. The hassle of getting IRS approval to secure deductions for donors could potentially pay off. So does networking with people in the community who work for organizations that use computers, so you're in the loop when they replace. My impression is that organizations in the public sector are required to auction stuff off. Here's a combined public sector auction listing:


  • Most of the "boxes" I bought used came with 2GB RAM. I upgraded to 4GB, a few to 8GB. 4GB seems sufficient for most purposes. Too little RAM forces operating systems to substitute hard disk space for RAM, which slows things down tremendously However once you install enough RAM to get out of this substitution mode, there's no benefit to further increases. Exceptionally demanding software or having many programs active simultaneously may actually use 8GB or more. I would recommend against buying smaller than 2GB memory sticks, since upgrades beyond 4GB are wasteful and complicated if you start with 1GB sticks installed, since motherboards normally have only four memory slots. Each system will have RAM specifications, that you must pay attention to and follow. RAM not meeting the system's specifications usually won't work. Expensive surprise!

  • Hard disk upgrades to ~250 or ~500 GB. Some of our used boxes came with 80GB drives. That would actually be enough for many purposes, but it was too small with all the architecture applications LATTC covers in class. We could have gotten away with 160 GB, but we found an excellent deal on 250 GB so that's the minimum we installed.

  • The compact and mini-tower desktop systems came with basic graphics on the motherboard. This would have sufficed for many applications (such as the Microsoft Office suite), with one display. However software for architecture classes demands more powerful "workstation" graphics cards, plus we wanted students to have a dual-display capability. We installed Quadro cards, which are NVidia's workstation line. NVidia and AMD also offer other lines of cards optimized for gaming. They are equally powerful, yet not as suited to architecture purposes. The compact desktop systems had size and power limitations so we had to install Quadro 600 and K600 models. The larger "mini-tower" systems could install full-height Quadro 2000 cards, which use more electricity but are more capable. The workstation graphics cards cost $20-30 used. The HP xw6600 workstations could install higher-end graphics cards drawing 200 or more watts. These are even more capable but much more expensive.

  • If you aren't using demanding architecture or engineering drawing programs and aren't trying to support gaming software, you may be able to get by with the "free" graphics built into the motherboard (single display), or a basic dual-display card costing in the neighborhood of $5 used. Dual displays is a significant productivity boost whenever you need to switch back and forth between windows/programs. The latest, greatest graphics cards are expensive. Their extra performance is only relevant in very specific circumstances. Software documentation should tell you if this is the case.

  • The desktop boxes all came with Intel Core 2 Duo CPUs, and the xw6600 workstation boxes all had two ea. of quad-core Xeon CPUs . We were careful to buy only systems that had or could be upgraded to later versions with 45nm technology. The previous 65nm or larger CPU generations were slower, hotter, and lacked SSE 4.1 instruction extensions. Current or future versions of some software requires SSE 4.1. Again, software documentation should mention whether this is the case.

  • Most Intel Core 2 Duo CPUs can be replaced with Core 2 Quad, doubling the number of cores and potentially speeding things up. Quad CPUs typically cost $10 and up, with low-power and faster models selling at a premium. However mini-tower systems generally had large enough power supplies and enough cooling so costlier low-power CPUs are not required when upgrading to four cores.

  • We did not buy boxes in Intel's newer i3, i5 or i7 CPU line. They offer about 2x more performance, but prices of used systems were out of our range.

  • Windows 10. We were able to buy valid licenses online for $5 or less each. We also could have purchased licenses for the MS Office suite at similar prices, but didn't because students have onlline access.


Sample budget:

Used minitower system $21

Upgrade RAM to 4GB 6

250GB hard disk 5

Basic 2-display graphics card 5

Keyboard, mouse 2

17" display, 1280x1024 11

Windows 10 license, MS Office 10______



Quad-core CPU 10


Quadro 2000 graphics card 25

Second display 11


Patience can really pay off. If you're in a hurry, you can expect to pay more.

I am writing from the Windows perspective, since I have virtually zero Linux experience. Generally, I would recommend building a prototype system, installing the operating system and software to be run, and testing thoroughly to check how the prototype system performs.

With a single system, you can evaluate performance with two-core vs. four-core CPUs, different amounts of RAM and different graphics options. You can also see how much disk space is actually needed. You can also install Windows, Linux, etc. on different hard disks and swap them around to evaluate those major alternatives. You can even install Apple's OSX on yet another hard disk. This is a bit tricky, but once you have it working on one system, you could replicate it on more. Google "Hackintosh" for more info. These can get you into trouble with Apple though.

As for networking, WiFi can be troublesome to maintain, while wired networks are simple, usually trouble-free, and faster. Most PCs come with wired Internet support on the motherboard, whereas you would need to buy and install WiFi cards to go wireless. Also, the more PCs you have accessing a single WiFi access point, the slower they get, since they must share a finite amount of WiFi bandwidth. Wired networks don't have this issue, since each wired connection is a separate circuit. So my recommendation is to wire all the desktops you install and only provide WiFi for people who bring in laptops or handhelds.

Interesting to speculate what could be done with handhelds such as Androids, accessing a fileserver via WiFi. I don't have experience with this, but there probably are people around who can advise.

A room full of computers in use is bound to draw a lot of power. Probably averaging at least 100 watts per desktop and 50watts per laptop. Peak demands will be greater, so you may need to allow twice as much maximum. Plus some more for printers, lights, fileservers and so forth.

All those watts end up as heat. A steady 1,000 watts is 3,412 BTU/hr, the unit for measuring performance of air conditioning equipment. Each person in the room is equivalent to another 100 watts. In Summer, you will want enough ventilation or cooling to remove this heat. In Winter you may be able to reduce or dispense with heating.

If you haven't already, check out the W6TRW electronics swap meet in Redondo Beach near the SE corner of Aviation and Marine, last Saturday mornings of every month. You never know what you might find there, and prices can be really low, with no shipping expense. Best to get there early, e.g. 8AM. Sellers start packing up and leaving after 10AM.

That's all I can think of. Probably mostly stuff you already knew anyhow. If you have other questions, I will do my best.


Dave Mason