Building a Mining Rig

[SchizophrenicX]

Hi everyone,

This thread started out with me trying to ask for help building my own mining rig, since mining is a highly specialized deal. I was not able to find off-the-shelf PC that is cost-efficient (I did find some) and neither did the wiki page help much.

Reasons I felt being some of them weren't within my budget or that in the age of GPU-Mining, CPU/RAM Power and other apparels are of less importance, the cost of these could go into more GPU power or simply lessen the burden of the investment by having a lower return of investment.

I also found a few other similar threads that eventually help me decide on what I'll be building in a few days from now. Many thanks to grndzero and many others who have been nothing but a great help to such a DIY-PC newbie like me to actually putting together one by myself.

I've found myself thinking of building more rigs with a focus of balancing cost-effective with future upgrade option and thus will continue to keep this tread alive with my findings and possibly discussions with many experts from this forum. I also intend to consolidate the different guides/treads/builds that are around into this one tread so that it'll be a lot easier for everyone who'd need this info.

Hopefully this tread will be of help to new people like myself in this massively confusing and technical world and also serve as an updated guide between the same fast-paced PC world and Bitcoin Mining world.

This is not yet complete but I intend for it to. Let me know what you think about it and give me suggestions and feedbacks. I gotta go get some sleep now and do some other stuff.

1. Before you start
You have to ask youself where is your balance for this machine, is this a
 - Dedicated Mining Rig
 - Mining/Gaming Rig
 - Entry/Trial Mining Rig
Head over to here and see some of the rigs that people are showing off and discussing to have a better idea of what I meant by balance.

2. Budget
After you've decided, you'll want to have a rough gauge of the amount of budget you'd want to throw into building this rig. The general guide is that don't spend over $1 per Mhash/s for your rig or it might not even be profitable enough to cover it's own cost in future [subjective] ($0.75/(Mhash/s) for best but hard to achieve)

3. Picking out the stuff
After budgeting you can have a general idea of how much Mhash/s will you be generating from this rig, with that we can start off with the Graphics Card (GPU) which is the core of generating Bitcoins, there isn't really much to say here as the Hardware Comparison Chart shows all the hashing rates for most of the modern cards.

The rest of the components are discussed but subject to availability in your local store, I agree to the general consensus of not accepting backorders as the difficulty adjustments recently are going all over the place and it is becoming very difficult to grasp the situation and make any predictions. The calculations that you've made would be best carried out as soon as possible.

  - 3.1 Graphics Card
    - Hardware Comparison Chart
    - 5830 @ 320 Mhash/s
    - 5850 @ 340 Mhash/s
    - Best GPU for price
  - 3.2 Motherboard
  - 3.3 Processor
  - 3.4 PSU
    - Best PSU to buy?
  - 3.5 Other Stuff
    - RAM
    - HDD
    - OS
      - Windows
      - Mac
      - Linux
         - LinuxCoin
         - Ubuntu 11.04 Natty 64bit Headless Bitcoin mining with ATI 11.5 binary driver
         - Ubuntu Natty Narwhal 11.04 Mining Guide / HOWTO
    - MISC

4. Build Treads
building a mining rig with $1800
Building a 4x GPU setup. Need some advice
What I Learned from Building 3x5850 Rigs; May 2011
Building first time under $1000 rig
Best bang for the buck? Whole rig
Best Coin/Buck rig V2
4x Radeon HD 6990
Problem running 4x 5830, please help!

5. References & Others
Windows Sidebar Gadget Supports (Deepbit/Slush/Eligius/BTCMine/BTCGuild)
FOR SALE: PCIe 1x & 16x Extender Cables, Mining Chassis & GPU Dummy Plugs
PCI-e 1x Extender not work in 16x connector
Auto Run Miners, Run Miners in Background/as Service?
run your miners invisibly with different arg when pc idle and pc used (Download)
run your miners invisibly only when pc idle (Download here)
How To Open 6 Terminals, Set GPU Clocks, And Start POCLBM On Ubuntu Startup???
Whitepixel breaks 28.6 billion password/sec
Sapphire ATI Radeon HD5850 Xtreme 1 GB Review

P.S If you found my post helpful, feel free to send me a tip | 13kHaYGkF9W5xNjF2Ck5hTgVR9MNjr8c3U |

P.P.S I realized I've quickly transited from a rig-building consolidation to looking more like a simple newbies guide so I've started this tread instead so I may continue updating here with my rig-building stuff.

EDIT: I've been pretty busy learning more stuff and updating the Beginner's Thread and have been lacking in this thread. However, I've added many links here regarding builds as I try to optimize my build and future builds.

Original Post
Hi everyone,

I'm in this weird position and need some help.

Where I stand,
1. I'm in need of a new desktop (mine's 'bout 9 years old), albeit not desperately
2. I intend to build a least 1 mining rig
3. I don't have that much cash to burn
4. Worried about Bitcoin's collapse (thus breaking even)

So I this is what I think, I get a basic comp jam some GPU hashing power in there and get it mining (2.). If (4.) were to ever happen I'll rip  the GPU out and build my 'new' desktop (1.), while the basic comp will be fitted with some basic GPU and be given away to my relative. In my mind this essentially utilize whatever 'cash' I have to play around with (3.)

Let me know if this makes sense to you and share some perspective

However, right now I'm presented with the problem of acquiring the mining rig, I've usually just bought desktops off the shelf and is not technically inclined to build my own desktop (which I know is cheaper [3.]). Seems like mining is highly specialized and there isn't much choice of readily available systems out there

I've read that GPU is the main focus on OpenCL mining and the subsidiary problems would be supplying it with power, cooling and the motherboard. What is less of a concern are the processor, RAM, OS and HDD.

So I came across a 2x5970 (Used) for $810 (good deal?) and would probably go for it. But I don't have any idea what other components to purchase for. Can you guys please help me make the most of my money, I'm not sure of how to complete the rig other than the GPU (From the comparison chart).

1. GPU - 2x5970 ($810)
2. Power Supply - Seasonic X-850 ?? 80+ Gold PSU ??
3. Mobo - 2xPCIe16x ?2.0/2.1/3??? This I totally have no idea
4. Processor - Sempron 140 ??
5. RAM - 1 GB ?? DDR2 or DDR3 ??
6. OS - I read there are readily scripted ubuntu/linux distro for mining. Please point me to the right thread plz
7. HDD - I also read that I may be able to just run (6.) off a USB stick/ext. HDD (Which I own) Plz clarify and point me to the right thread
8. Casing - I don't wish to go for good cooling casing, I might just leave the case open with my huge-ass fan on it

The stuff I have up here are from reading the forum. Please advice on the build and really, where can I get the stuff. Thanks in advance

[1714787822]

1714787822

[kiwiasian]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

[SchizophrenicX]

Right... So, I have no idea what you've just mentioned. I'm sorry.

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

[grndzero]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

Yes, he is serious. It hardly takes any CPU power to mine. Buy a AM3 compatible board and put a sempron in it for mining. When he's done mining he can pull out the sempron and put an Athlon or Phenom in it. That way he's not wasting money and power up from on an Intel setup.

[SchizophrenicX]

Yes, he is serious. It hardly takes any CPU power to mine. Buy a AM3 compatible board and put a sempron in it for mining. When he's done mining he can pull out the sempron and put an Athlon or Phenom in it. That way he's not wasting money and power up from on an Intel setup.

Thanks, I guess I've been reading the right stuff. I don't know what is an AM3 compatible board. But I think you've at least taken a read at my long-winded post which I'm grateful for. So I'm really confused about the whole motherboard thing as I'm reading on DIY computers right now.

The Athlon or Phenom I assume are processors that I may upgrade to later on, I'm worried about the bottlenecking issue that I'm reading on 2x5970. But I think this is a problem for later, I need to complete this mining build first so I can get mining.

Care to shed some light on 'bare minimum' (for mining) and around how much they'd cost? Better yet, link me the URL. I'm situated in South-east Asia and I'm not sure about the whole DIY scene.

[grndzero]

Yes, he is serious. It hardly takes any CPU power to mine. Buy a AM3 compatible board and put a sempron in it for mining. When he's done mining he can pull out the sempron and put an Athlon or Phenom in it. That way he's not wasting money and power up from on an Intel setup.

Thanks, I guess I've been reading the right stuff. I don't know what is an AM3 compatible board. But I think you've at least taken a read at my long-winded post which I'm grateful for. So I'm really confused about the whole motherboard thing as I'm reading on DIY computers right now.

The Athlon or Phenom I assume are processors that I may upgrade to later on, I'm worried about the bottlenecking issue that I'm reading on 2x5970. But I think this is a problem for later, I need to complete this mining build first so I can get mining.

Care to shed some light on 'bare minimum' (for mining) and around how much they'd cost? Better yet, link me the URL. I'm situated in South-east Asia and I'm not sure about the whole DIY scene.

I don't know what retailers and online computer shops you have available to you in southeast asia, so I can't really link anything for you directly.

The best motherboards and CPU's for the price for mining purposes specifically are AMD motherboards and Sempron processors. The CPU socket type (pin configuration of the CPU) is called AM3. Basically you need a motherboard that will support the number of cards that you want to mine with. You also should think about future expansion. Motherboards with 2 video card slots are pretty common.

The best entry level cards for mining right now are the HD 5830, HD 5850, and HD 5870 but that depends on the availability and pricing in your area.

You will need a good power supply to run them. It would not be a good idea to pick the cheapest on on any list from any store, you need to look at reviews. Depending on what cards you get and how many you get you will be looking for a power supply in the range of 750-1000 watts.

Here are some threads you should read through to get a better idea what people are planning to put together for mining rigs.

http://forum.bitcoin.org/index.php?topic=8546.0
http://forum.bitcoin.org/index.php?topic=8169.0
http://forum.bitcoin.org/index.php?topic=8506.0

[SchizophrenicX]

I've not thought of future expansion and was only thinking of getting my first rig up and running before anything else. This is mainly due to my availability of capital for investment toward bitcoin right now.

I already have a deal for 2x5970 which averages 650 Mhash/s ea. according to hardware comparison chart, this puts me nicely into 1.3 Ghash/s and the build considerations starts from there.

SO I'm pretty sure I could only manage this much (2x5970, 1 rig) right now, but thanks to your reminder and the treads. I realized that I might need to consider better MOBO+PSU for expanding more GPU in the soon future.

However, before that I need to ask, isn't 2x5970=4GPU and I'm not sure but does MOBO usually support more than that? And PSU that can support future expansion? Can I find a value-for-money configuration for such a consideration to exist. If not, shouldn't I just go for the cheapest config I can get starting from a 2x5970 point?

If such case, now it's looking like

1. GPU - 2x5970 ($810)
2. Power Supply - Seasonic X-850 ?? 80+ Gold PSU ?? (Not sure what's 80+Gold but should be around 850 Watts OC?)
3. Mobo -  Dual PCIe2.x16x AM-Compatible MOBO
4. Processor - Cheap Sempron (Not sure which)
5. RAM - 1 GB
6. Casing - As cheap as possible, open aired or might not even get one.

Still need to find out
7. OS - I read there are readily scripted ubuntu/linux distro for mining. Please point me to the right thread plz
8. HDD - I also read that I may be able to just run (7.) off a USB stick/ext. HDD (Which I own) Plz clarify and point me to the right thread

But if it's possible to get more GPU on 1 machine after 2x5970 I'd appreciate it if you point me to the right thread so I may look at the possibility of future expansion.

[grndzero]

However, before that I need to ask, isn't 2x5970=4GPU and I'm not sure but does MOBO usually support more than that? And PSU that can support future expansion? Can I find a value-for-money configuration for such a consideration to exist. If not, shouldn't I just go for the cheapest config I can get starting from a 2x5970 point?

If such case, now it's looking like

1. GPU - 2x5970 ($810)
2. Power Supply - Seasonic X-850 ?? 80+ Gold PSU ?? (Not sure what's 80+Gold but should be around 850 Watts OC?)
3. Mobo -  Dual PCIe2.x16x AM-Compatible MOBO
4. Processor - Cheap Sempron (Not sure which)
5. RAM - 1 GB
6. Casing - As cheap as possible, open aired or might not even get one.

Still need to find out
7. OS - I read there are readily scripted ubuntu/linux distro for mining. Please point me to the right thread plz
8. HDD - I also read that I may be able to just run (7.) off a USB stick/ext. HDD (Which I own) Plz clarify and point me to the right thread

But if it's possible to get more GPU on 1 machine after 2x5970 I'd appreciate it if you point me to the right thread so I may look at the possibility of future expansion.

2 x 5970 is 4 GPU's, yes.

As long as the motherboard has the slots for it, it will support as many video cards as you put in it. There are many people running 6 processors on 1 board (3 x 5970 or 6990 cards) and a thread http://forum.bitcoin.org/index.php?topic=8847.0 of someone reporting running 4 x 6990 (8 gpus) on 1 system. The OS is the limiting factor. Windows will only support up to 4 GPU's, Linux will handle up to 8.

You should go for the best quality (reviewed) for the price, not the absolutely cheapest.

1. Wish I had them. Looks good.
2. Should be good to run a system with 2 x 5970's. Won't allow for an expansion to 3 though.
3. AM3 compatible board, rest is correct.
4. Sempron 140 or 145 is fine.
5. I went with 2 G of ram just because it was worth buying for the price. You probably want 2G if you go with Windows, 1G is good for Linux
6. It's personal choice. I like having a case and leave the side panel off.
7. Another personal choice. I like Linux better and think it's better for dedicated mining machines. If you decide to go Linux, Ubuntu is the most popular and well supported here, I recommend that one. http://forum.bitcoin.org/index.php?topic=7514.0 The dedicated one still has some work to be done on it to make it easier from what I've read.
8. I haven't tried it yet (but I will soon). Ubuntu can probably be run from a USB stick or USB hard drive without much trouble. You need at least 8G. I don't know of any specific threads. You would have to plug them in and install it to the USB device. Windows will require a hard drive or SSD.

[jspielberg]

https://en.bitcoin.it/wiki/Mining_rig
This link used to be pretty good.

Looks like it was recently updated for the 6900 class Radeon hardware.  The older version I think was more what you were looking for as it was specifically listing 5970's. (No luck finding it on the way back internet machine though... sorry).

[SchizophrenicX]

Alright, the more reading I do the more confused I get.

I've got around 2k that I'm willing to invest into building a new computer/mining rig.

I've got a dual core 3Ghz 2GB RAM 4850 doing 75 Mhash/s (No idea what MOBO) and as my main computer. and another MBP 320M doing like 6 MHash/s as my mobile computer.

I don't know how many GPU can a motherboard/OS support and stuff like that so I really need help... I'm not sure if I should build with plans for future expansion. I might have another deal for 2x4850 for really cheap but these only does another 150 Mhash/s. I don't want to overcommit myself to mining yet and the idea pop since initially I've had plans for a new desktop.

I've got a deal for 2x5970 @ $808
I don't know and can't find any site where I can learn or play around with to see what works and what doesn't.

Apparently a lot of people goes to newegg, I don't know how to navigate that site but since every cheap rig uses Sempron 140 I'll assume it's best. I also don't know if I can find these parts around here or if they ship to my country yet. Will read on that later.

GPU: 2x 5970 ($808)
MOBO: Still having problems
CPU: Sempron 140 ($39)
PSU: At least 850 W (Recommended) Should need more factoring OC
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

Optional GPU: HD5850 @ $160 ea.

$867 + MOBO + PSU + ($160x#) for ~1.3 Ghash/s + (#x300Mhash/s)

I've got around $1133 left, is it better to get better (& costlier) MOBO+PSU and get a few 5850 or get minimum required for 2x5790 and save the $ for building another rig? (Considering having more GPU on one machine is going to have major heat issues)

Plz give me a hand on this. Thanks a lot.

P.S Yea, I saw the mining_rig wiki just yesterday but it's been updated. Those are quite costly aren't they?

EDITED: 2 New post while writing this. Thanks for the replies grndzero & jspielberg

[SchizophrenicX]

So if I go for minimal cost no future expansion it'll look something like this

GPU: 2x 5970 ($808)
MOBO: Foxconn A7DA-S 3.0 ($45)
CPU: Sempron 140 ($39)
PSU: Diablotek PHD ($70)
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

$982 for ~1.3 Ghash/s [1.324 Mhash/$]
Not sure about the power consumption but it cost $0.20/kWh

So if I wanna go for more GPU then I'll need more PCIe2.0x16 slots? or what other slots? The PSU and MOBO with >3 of these slots are much more expensive though I wonder if it's more cost effective to just build another similar machine.

P.S 140.285714 BTC to breakeven. Can someone tell me how long it takes to get this amount of BTC I already have a 140 MHash/s so total is around 1.5 Ghash/s if I build this. And if I should continue to mine in pool and at which point should I start mining solo? Hmm

[grndzero]

So if I go for minimal cost no future expansion it'll look something like this

GPU: 2x 5970 ($808)
MOBO: Foxconn A7DA-S 3.0 ($45)
CPU: Sempron 140 ($39)
PSU: Diablotek PHD ($70)
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

$982 for ~1.3 Ghash/s [1.324 Mhash/$]
Not sure about the power consumption but it cost $0.20/kWh

So if I wanna go for more GPU then I'll need more PCIe2.0x16 slots? or what other slots? The PSU and MOBO with >3 of these slots are much more expensive though I wonder if it's more cost effective to just build another similar machine.

P.S 140.285714 BTC to breakeven. Can someone tell me how long it takes to get this amount of BTC I already have a 140 MHash/s so total is around 1.5 Ghash/s if I build this. And if I should continue to mine in pool and at which point should I start mining solo? Hmm

Mobo doesn't support Sempon: I would recommend this http://www.newegg.com/Product/Product.aspx?Item=N82E16813130290
PSU has really bad reviews: I would recommend this one http://www.newegg.com/Product/Product.aspx?Item=N82E16817152043
Memory needs to be at least DDR3 1033. You probably don't have they laying around if your computer is 9 years old. http://www.newegg.com/Product/Product.aspx?Item=N82E16820148147

Buying the cheapest parts invites trouble. Spend as little as possible but make sure you're buying quality parts.

[SchizophrenicX]

What does it mean when it says this
PCI Express 2.0 x16: 2 (x16, x4)
is this alright? Cuz if it then would this mobo work too? Looks very much the same but cheaper.

And this PSU have great reviews too though it's not Gold but it's 80 Ready which actually I don't really know what's the difference -.-

Yes I'm trying to skim course USD is a larger currency than mine, every 10 bux difference helps.

Would you be kind enough to tell me if those work too? and if so, what's the difference? For 1 GB DDR3 probably someone I know would have one lying around haha. Everyone's been going 4~8 GB I'm sure there are plenty of 1 GBs around

[grndzero]

What does it mean when it says this
PCI Express 2.0 x16: 2 (x16, x4)
is this alright? Cuz if it then would this mobo work too? Looks very much the same but cheaper.

And this PSU have great reviews too though it's not Gold but it's 80 Ready which actually I don't really know what's the difference -.-

Yes I'm trying to skim course USD is a larger currency than mine, every 10 bux difference helps.

Would you be kind enough to tell me if those work too? and if so, what's the difference? For 1 GB DDR3 probably someone I know would have one lying around haha. Everyone's been going 4~8 GB I'm sure there are plenty of 1 GBs around

X16, x8, and x4 are speeds of the PCI Express slot. That doesn't matter for mining.

That board would work, but it puts the cards right next to each other and doesn't allow much room for airflow. Something you should avoid with 5970's especially.

You should also ask friends, family, and co workers what computer part sites are available in your region. Upwards of 90% of computer parts in the US come from the Asian continent. There has to be someplace in your region that you can get stuff from, possibly at cheaper prices. Depending on what currency you are using, you may get better exchange rates buying in Euros or Australian Dollars. You would very likely get better shipping from Australia than the US.

[ensign_lee]

Remember guys, he's trying to build a new desktop for COMPUTING, not exclusively for mining.

OP, try this:

Intel i5 - 2400 (or INtel i3-2100 for cheaper) (or Intel i5-2500k if you really want to splurge and want a high performance CPU for NOT mining purposes)
$150 (or $100 if you get the i3) (or $180 if you get the 2500k) from Microcenter
Mobo: Gigabyte P67 UD3
$120 from Microcenter
RAM: Cheapest RAM you can get, 4GB will do ya
Probably around $35 to $40
Case: Something with lotsa fans?
$50?
Power Supply: Don't skimp on this. Everything could die if this thing fails. And if you're going to run two cards that each require 2 6pin or 8pin slots, ideally find a power supply with FOUR of those slots.
$60-$100

Graphics cards: Cheapest bang for your buck at the moment is probably the 5850 for ~$150 each. Should get you around 300 MHash/s each.

This computer will be good at mining, and GREAT at gaming, whatever else you need it for in the future.

[grndzero]

Performance Miner

http://www.newegg.com/Product/Product.aspx?Item=N82E16811119233 - $59.99 - COOLER MASTER HAF 912
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371050 - $129.99 - Antec High Current Gamer Series HCG-900 900W
http://www.newegg.com/Product/Product.aspx?Item=N82E16813130290 - $74.99 - MSI 870-G45
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103871 - $99.99 - AMD Athlon II X4 640 Propus 3.0GHz
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148149 - $21.99 x2 - Crucial 2GB 240-Pin DDR3 SDRAM DDR3 1066

Quad Core Athlon, 4G RAM, 900 W PSU - $408.94
   

[jasonk]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

Total waste of money to buy an i7, UNLESS your going to use it to game.

Sempron 140 is fine.  I'd say get 2GB of RAM though, as when I was shopping it was like $20 for 1GB and $25 for 2GB.

So if I go for minimal cost no future expansion it'll look something like this

GPU: 2x 5970 ($808)
MOBO: Foxconn A7DA-S 3.0 ($45)
CPU: Sempron 140 ($39)
PSU: Diablotek PHD ($70)
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

$982 for ~1.3 Ghash/s [1.324 Mhash/$]
Not sure about the power consumption but it cost $0.20/kWh

So if I wanna go for more GPU then I'll need more PCIe2.0x16 slots? or what other slots? The PSU and MOBO with >3 of these slots are much more expensive though I wonder if it's more cost effective to just build another similar machine.

P.S 140.285714 BTC to breakeven. Can someone tell me how long it takes to get this amount of BTC I already have a 140 MHash/s so total is around 1.5 Ghash/s if I build this. And if I should continue to mine in pool and at which point should I start mining solo? Hmm

Mobo doesn't support Sempon: I would recommend this http://www.newegg.com/Product/Product.aspx?Item=N82E16813130290
PSU has really bad reviews: I would recommend this one http://www.newegg.com/Product/Product.aspx?Item=N82E16817152043
Memory needs to be at least DDR3 1033. You probably don't have they laying around if your computer is 9 years old. http://www.newegg.com/Product/Product.aspx?Item=N82E16820148147

Buying the cheapest parts invites trouble. Spend as little as possible but make sure you're buying quality parts.

Yes it DOES support the sempron.  I run a Sempron 140 in mine, no problems... I have that same Foxconn board.

[grndzero]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

Total waste of money to buy an i7, UNLESS your going to use it to game.

Sempron 140 is fine.  I'd say get 2GB of RAM though, as when I was shopping it was like $20 for 1GB and $25 for 2GB.

So if I go for minimal cost no future expansion it'll look something like this

GPU: 2x 5970 ($808)
MOBO: Foxconn A7DA-S 3.0 ($45)
CPU: Sempron 140 ($39)
PSU: Diablotek PHD ($70)
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

$982 for ~1.3 Ghash/s [1.324 Mhash/$]
Not sure about the power consumption but it cost $0.20/kWh

So if I wanna go for more GPU then I'll need more PCIe2.0x16 slots? or what other slots? The PSU and MOBO with >3 of these slots are much more expensive though I wonder if it's more cost effective to just build another similar machine.

P.S 140.285714 BTC to breakeven. Can someone tell me how long it takes to get this amount of BTC I already have a 140 MHash/s so total is around 1.5 Ghash/s if I build this. And if I should continue to mine in pool and at which point should I start mining solo? Hmm

Mobo doesn't support Sempon: I would recommend this http://www.newegg.com/Product/Product.aspx?Item=N82E16813130290
PSU has really bad reviews: I would recommend this one http://www.newegg.com/Product/Product.aspx?Item=N82E16817152043
Memory needs to be at least DDR3 1033. You probably don't have they laying around if your computer is 9 years old. http://www.newegg.com/Product/Product.aspx?Item=N82E16820148147

Buying the cheapest parts invites trouble. Spend as little as possible but make sure you're buying quality parts.

Yes it DOES support the sempron.  I run a Sempron 140 in mine, no problems... I have that same Foxconn board.

Newegg only list Phenom as supported processor, I thought it was kind of weird but ok.

[Basiley]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

he's shoulld be okay with sempron, but im suggest[only $9 more expensive Athlon II 220 or 210/230(for similar prices], cause single-core cpu can behave erratically in modern OS'es and/or become bottleneck[for IO overhead mainly ;]. imagine OS failure because lack of CPU horsepower for APCI routing
clearly its not Crossfire[suitable only for gaming], but OpenCL computing PC.
OpenCL not supported by games[as Crossfire did], but thats only disadvantage for gaming. and thats games creators problem, not topicstarter.
CPU load usually under 1%, with short 3%-5% spikes for seconds.

[SchizophrenicX]

Quad crossfire 5970's with a Sempron 140 and 1gb of RAM?

Are you serious?

At least put an i7 in that system. Go with Sandy Bridge even or wait for Ivy.

Total waste of money to buy an i7, UNLESS your going to use it to game.

Sempron 140 is fine.  I'd say get 2GB of RAM though, as when I was shopping it was like $20 for 1GB and $25 for 2GB.

So if I go for minimal cost no future expansion it'll look something like this

GPU: 2x 5970 ($808)
MOBO: Foxconn A7DA-S 3.0 ($45)
CPU: Sempron 140 ($39)
PSU: Diablotek PHD ($70)
RAM: 1 GB Lying Around ($0)
HDD: None/USB ($0)
CASE: None/Cheapassjunk (~$20)
OS: Linux Ubuntu ($0)

$982 for ~1.3 Ghash/s [1.324 Mhash/$]
Not sure about the power consumption but it cost $0.20/kWh

So if I wanna go for more GPU then I'll need more PCIe2.0x16 slots? or what other slots? The PSU and MOBO with >3 of these slots are much more expensive though I wonder if it's more cost effective to just build another similar machine.

P.S 140.285714 BTC to breakeven. Can someone tell me how long it takes to get this amount of BTC I already have a 140 MHash/s so total is around 1.5 Ghash/s if I build this. And if I should continue to mine in pool and at which point should I start mining solo? Hmm

Mobo doesn't support Sempon: I would recommend this http://www.newegg.com/Product/Product.aspx?Item=N82E16813130290
PSU has really bad reviews: I would recommend this one http://www.newegg.com/Product/Product.aspx?Item=N82E16817152043
Memory needs to be at least DDR3 1033. You probably don't have they laying around if your computer is 9 years old. http://www.newegg.com/Product/Product.aspx?Item=N82E16820148147

Buying the cheapest parts invites trouble. Spend as little as possible but make sure you're buying quality parts.

Yes it DOES support the sempron.  I run a Sempron 140 in mine, no problems... I have that same Foxconn board.

Newegg only list Phenom as supported processor, I thought it was kind of weird but ok.

hmm which MOBO are u guys talking about? The cheapass one? Cuz I'm trying to drive down the investment for the rig. other than the gfx card. which I already planned on investing in the first place. The rest of the stuff I wanna get as cheap as possible.

My question now is how many PCIe should I try to get cuz I could expand with maybe 5850s for the rig. but is it worth the increase cost of the MOBO and PSU or is it just cheaper to get another cheapass rig