Motherboard questions

[MerePeer]

Does a motherboard require a video card in it to post? In the pictures of farmer stacks I'm wondering if they use motherboards with onboard video, motherboards with vid cards, or dont bother with the vid card unless they are diagnosing/working on it.

Heres an nvidia mobo w/ 2900+ for $99 I am looking into, and it doesn't have video.

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1166612&Tab=2&NoMapp=0

Also is it safe to assume that an onboard network + today's BIOS will allow pxe/net booting? (I haven't done that yet but was considering it.)

Also I saw LAURENU2 say he puts 2 motherboards on one power supply. Is this done using some kind of splitter for the ATX power connector because or do some power supplies come with 2 of those 20(?) pin connectors? I wonder how big a power supply would need to be to support 2 motherboards no hardrives?

Thx.

[PCZ]

Most motherboards will post without a videocard.
However if you want it to boot you have to tell the bios not to stop on error.

I don't bother with video cards on my pxe nodes.
If the motherboard has on board video I disable it to increase the memory bandwith available to applications.

Obviously when setting up the board you need video I use on old pci video card for that.

LTSP should work OK with the realtek nic.

You can buy power splitters or make them yourself , IB had some made for him.

Personally I don't use splitters but they should be OK if the PSU is meaty enough.
Also some motherboards use the 12v plug so you would have to split that as well.

[MerePeer]

Thx for the previous replies PCZ. Now some more:

- I see in the pictures of stack threads, like LaurenU2's here http://www.free-dc.org/forum/showthread.php?s=&threadid=8281, that some motherboards have a disk drive attached "out in the open". Is this ok to do, for instance dont they need to be anchored to prevent vibration or to ground them or simply to keep them from eventually hopping across the board and falling off?

- without a case I'm realizing there will be no "start" button...what do you do about this? I couldnt find a "power switch" or atx button in newegg searches. I actually have a spare front panel, but thats awkward.

- I read one thread somewhere that said if you change your overclocking params (frequency for example), which result in a different machine's MHZ, then you will need to reinstall Linux. Is this true?

- whilst initally playing with frequency and getting the overclock just right I know that monitoring temps is important -- are there any linux utils to do this? Is it a better idea to install Win; do overclock activity and burn in; then a few days later after it has been running stable rewrite hard drive and install Linux?

- when using a PXE setup and the power fails: both the server and the nodes will all try to come up at once -- but since those (NFS?) mounts on the server aren't available for, say, 60 seconds while the server boots...do the nodes simply fail and shutdown and you have to go restart them when you notice this?

Thx. I'll do some reading on LTSP while waiting for my hardware to arrive.

[PCZ]

MerePeer

Lots of questions ;)

You can have a hardrive attached by just the ribbon and power cables.
If the surface it is siting on is flat there is no problem.

I used to run a few boards like this, before I made them all discless.
If you are worried about vibration just sit the drive on some bubblewrap.

As to the start button.
You don't need one just set 'restart on AC power loss' in the bios and the node will autostart when the power supply is turned on.

If for some reason you dont have this option in the bios just put an electrolytic capacitor across the startup pins.
There is a picture showing this at the end of one of the PXE threads.

As to reinstalling linux because you changed the clock speed of the CPU, this is bull.
There is absolutely no need to do this.

Oh yes the what happens if the power goes out question.
You are correct in assuming that the nodes won't boot because the server will not be up.

What can you do about this

1: You could buy a UPS for the Server
2: Use a computer with a built in UPS as the server, otherwise known as a Laptop :)

I favour option 2
The PXE server does not need to be powerful and an old laptop works fine providing it has enough ram.

[MerePeer]

Thx! :)

[Bok]

PCZ answers everything, but I'll a little too.

For power switches on my blades I just pulled a number of the power button / reset button wires from a few old cases and use them if required..

Never need to re-install linux - ever! if you wish. Only ever reboot if you upgrade the kernel.

I mount some of my blades inside stackable baskets using those little ties for wiring on the HD and mobo. Looks fairly neat and the the baskets are less than $10 each.

What are you using as blades ?

Bok

[MerePeer]

Thx for the tip on the old cases -- I actually had found one this way too! And while I was digging through the scrap pile I found an old ATI Rage 3d vid card I can use if the IGP fails.


What are you using as blades ?

I grabbed a $63 Biostar M7NCG 400 which is micro sized, OC-capable BIOS, onboard VID, nvidia chipset. Then I inserted a $67 boxed Sempron 2400 which is 166x10 (1.67Ghz) and appears to be happy at 189x10 (1.89Ghz or > Sempron 2600) with no voltage increase (avoiding silicon damage), and curiously the IGP still working. Boxed AMDs have heatsink + fan. Add a $27 3200 Rosewill 256MB + a $10 Rosewill RV300 power supply (2 fans, nice amps, lots of over-protection).

I took a slightly different approach on the PXE boot, electing not to use LTSP but still using TFTP and pxelinux. The node is booting a custom Debian 2.6 kernel I had to build so that it included NFS, NFS as root, and the reverse engineered nvidia onbard lan driver (I won't mention how long it took me to figure out this was an issue!). I'm wondering if a smaller kernel is a faster kernel so I've also been trimming baggage from the default Debian kernel, like DECNET, IPX, Appletalk, ATM etc. At first I tried using a tinysofa kernel http://www.tinysofa.org/, but it too would need the NFS support built-in and thus I'd need to build a kernel and so I've waitlisted that project for a rainy day.

I still have an open issue I need to solve re: my DNS not getting auto-updated with the PXE node's name (because the dhcp activity takes place pre-node-O/S install and thus the /etc/dhclient.conf is not doing its "send host-name xyz " activity; but I'll post in the networking forum if I cant solve.

I was really impressed yesterday when the NFS server went down and the node just waited until it came back and then kept doing D2OL!

I added it as a separate node in D2OL so I could track its average -- which after 3 days is 50 although its been up/down alot as I experiment. D2OL is so random re: length of time to complete a WU that its hard to really know how fast this node is producing. I should look for some Linux benchmarking software someday; hey maybe I should dig out that DF benchmark thing! I eventually need to decide on a mounting approach -- those baskets sound like an interesting idea Bok, are they made of plastic? Meanwhile here are the basic dumps:

Tinkerbell:~# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : AMD Sempron(tm
stepping : 1
cpu MHz : 1891.100
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
bogomips : 3743.74

Tinkerbell:~# sensors
w83627hf-isa-0290
Adapter: ISA adapter
VCore 1: +1.60 V (min = +1.47 V, max = +1.63 V) ALARM
VCore 2: +1.52 V (min = +1.47 V, max = +1.63 V)
+3.3V: +3.31 V (min = +3.14 V, max = +3.47 V)
+5V: +4.95 V (min = +4.76 V, max = +5.24 V)
+12V: +12.04 V (min = +10.82 V, max = +13.19 V)
-12V: -12.28 V (min = -13.18 V, max = -10.80 V)
-5V: -5.10 V (min = -5.25 V, max = -4.75 V)
V5SB: +5.51 V (min = +4.76 V, max = +5.24 V)
VBat: +3.12 V (min = +2.40 V, max = +3.60 V)
fan1: 0 RPM (min = 10546 RPM, div = 32)
fan2: 3013 RPM (min = 5273 RPM, div = 32)
fan3: 0 RPM (min = -1 RPM, div = 16)
temp1: -48 C (high = -112 C, hyst = +0 C) sensor = thermistor ALARM
temp2: +34.0 C (high = +120 C, hyst = +115 C) sensor = thermistor
temp3: +35.5 C (high = +120 C, hyst = +115 C) sensor = thermistor
vid: +1.550 V (VRM Version 8.2)
alarms:
beep_enable:
Sound alarm disabled

Note: those temps are in a 60F (16C) room. Temps in a 70F (21C) room were 40C. Not in a case.