Populating and Expanding a Server Board + Yea or Nay on ECC

[atomictom]

I got hold of a 12 core opteron engineering sample(2.0Ghz) earlier this year and I'm finally getting round to getting all the components i need for it and the last bits i have to buy are the motherboard and the RAM.
The motherboard is going to be a Supermicro H8SGL-F which is pretty much perfect for my needs.

RAM-wise though i have to admit my knowledge not entirely complete and since this is a fairly costly sum of components i don't want to screw it up.

Now I've got a choice between either Registered ECC or just normal RAM as the former can populate the board with up to 256GB (I would only ever max populate this up to 128GB since I'd have to sell half my organs for 32GB modules). Is there much of a performance hit with Registered ECC and is it worth the extra money to go for it considering the expandability option as well? And will ECC improve system stability over longer periods of time, as i on occasion wish to leave it on for weeks at a time.

Second point is the cost. A 16GB Hynix module from scan is gonna cost me £125 a pop and ideally i'd be buying only two of them initially. That's the cheapest i could find(+/- £3). Will that motherboard work with just 2 DIMMS occupied since in the manual it says 'always install in groups of 4'(the manuals play it safe half the time but i'm not really willing to bet a couple hundred pounds on that this time). Otherwise i would have to downgrade to using 8GB sticks at first which actually ends up being more costly per GB than the 16GB modules (or can someone prove me wrong on that one?).

Finally, the last question:
1333mhz vs 1600mhz? there seems to be only a 10% difference in cost(£6-£7 per 8GB module)so is the benefit of the extra monies worth it?

And just for reference this machine is going to be used for running half a dozen or so virtual machines(most likely via Proxmox) some will be running low-end game servers for older games or maybe minor web-hosting. but whatever i run on it i plan on having a sizable ram-disk.

Thanks in advance guys!

[bytejunkie]

because it specifically states groups of four, I'd install four 8's in it at first.

from various discussions recently, i just dont see a benefit in buying 1600 GHZ chips. so don't stretch the budget for them. for what you're going to be running, the fact you've only got a single processor strikes me as the probable bottleneck. i wouldnt bother with ECC either. sometimes the load the error checking adds just isn't needed. and you're on a single processor...

[atomictom]

Thanks for the advice. In the end i went with ECC because i managed to get 32GB(4x8GB) of some 1333mhz Samsung stuff off of flea-bay for only a couple more quid than unbranded RAM. hopefully there won't be too much performance loss, but i was inclined to go with it anyway for stability if i'm running off ram-disks for days/couple weeks at a time.

thanks a lot though!