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Salvaged Server PC

Cheap PC from company cast-offs

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My local museum gets given a lot of stuff that isn't at all historic, so they get left out for people to help themselves. I picked up an old PC to see if I could get it working.

I did, and I lent it to a neighbour's kid who has got it running as a server!

Businesses are allowed to write off worn-out or obsolete equipment as a business loss, so they make less profit that can be taxed. Every year, tons of working IT equipment is scrapped after a few years service.

My local museum is contractually obliged to take in some of this, despite not being historic enough to merit exhibition space. Businesses get rid of many desktop and server PCs. The museum puts them out on a 'help yourself' table from time to time. I went to see if there was anything useful.

There were five HP Proliant ML110 G6 server PCs with Xeon CPUs. However, they are not complete for various reasons. There are no disk drives because companies remove them to ensure no confidential information is leaked. Some scavengers just pick out the more valuable bits they want and leave the rest - which annoys the museum which gets left with the PC which is even less likely to get taken away. Do not do this! It is like picking jewels out of jewellery - the parts are worth less individually than they are together. It is more sense to take a whole PC, get it working, then sell it on. 

I picked one that seemed the most intact, but it was still missing a PSU and RAM. Some had a PSU but no CPU heatsink, and so on.  I didn't have time (or screwdriver) to go through them all to try and complete my chosen PC.

I had a standard PSU of the right size but the connectors did not fit the motherboard (not enough contacts) or modern SATA hard drives. So I bought a new 300W PSU that was the correct HP part. There are plenty of suitable parts on eBay because there are companies that take old tax-write-off machines and sell their parts for repairs. I got the exact HP part I needed for £10.

Server PCs generally use RAM with error-correction circuitry (ECC), because reliability outweighs the extra cost. For personal use, I gambled that it would work with normal non-ECC RAM. My machine had four slots, for a maximum of 16 GB. I did not need that much. 

It is faster to have RAM in interleaved modules, so I bought 8G RAM as two 4 GB modules. That cost £16. 

Assembled, it briefly ran the fans then just blinked an LED. I guessed the CMOS RAM settings no longer matched the actual hardware. So I removed the coin cell to clear the settings. I also noticed it was 2.5 volts, and therefore dead, so I replaced it with a fresh 3V 2032 size coin cell. Things improved, in that the fans then remained on. No video though. Perhaps it had no RAM where expected?

Moving the RAM modules to alternate slots (not the ones the manual said to use) fixed the problem, video appeared. I tried booting from several old bootable disks, and they booted.

Thus I now have an 8 GB working PC for just over £26.

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  • Memory modules

    Keith07/09/2022 at 21:14 0 comments

    PC memory is a lot more complicated than simply plugging in anything that will physically fit.

    A modern desktop CPU often accesses memory 2 or 3 times faster than any one module can handle. They get round this problem by having 2 or 3 modules running simultaneously, each a half or a third of their memory cycle out of phase. Therefore modules need to be fitted in matched pairs or triplets.

    Most PCs have 4 or 6 slots, allowing two banks of pairs or triplets.

    For example, my floor-top PC has  three 2GB modules and the salvage PC has two 4GB modules. Both have twice as many slots but I have not needed more memory. 

    Most importantly it is best to buy memory that runs as fast as the CPU can. Any slower, and the CPU has to slow down. Any faster, and you will be paying more for faster memory speed that the CPU cannot make use of.

    Do not try plugging in modules that you just happen to have around.

    Read your motherboard and CPU manuals - carefully - to see what modules will work, before buying or  fitting any.

  • Specification

    Keith02/06/2022 at 17:33 0 comments

    The salvaged CPU is an old Xeon i7, which is reasonably useful. It can be bought on eBay for about £13. 

    My floortop 4-core 2.66 GHz i7 CPU cost me £180 in 2009. I still find it fast enough 12 years later, which is a very long time in technological terms.

    The i7 was the fastest mainstream CPU I could afford in 2009, running around 2.5 to 3.5 GHz. I'm surprised that this is still a common specification today. Why are we not on the i12 and 12 GHz by now? It seems that faster clock speeds mean higher electrical power than is practical to cool. And it isn't that easy to get extra performance from new architectures. So advancements come in the form of putting more cores on chips, more threads, while keeping the energy use about the same.

    Xeon chips are optimised for servers - more cores rather than speed. So although they are more expensive they are not usually best for personal use.

    I've now got a salvaged PC for £26, with about the same performance as the one I bought in 2009 for about £1000. 

    The video output is analogue VGA, but the resolution is less than the usual 1920 x 1080 pixels of modern displays. Graphics are not particularly important on servers. So I may buy the cheapest video card that has a DVI and HDMI output.

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