What's the slowest/oldest CPU to get for a GPU mining rig?

[bustaballs]

Should we go as far back as Athlon XP / P4? Should the rules be as long as the mobo supports the video card you want to use, the CPU doesn't matter at all? I'm looking around for used desktops with enough of a PSU to throw a card in. I've been checking craigslist and such so advice on the CPU is welcome. Thanks.

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[kirby9058]

I have a workstation with an Athlon XP in it, and the 4650 in it is mining just fine.

[smoki]

Well, the Athlon XP motherboards are AGP only, so no good mining video card will fit.
P4 on the other hand, comes in several varieties, including socket 775, so at least these will fit into pretty much any socket 775 motherboard. It will be powerful enough for mining, even on multiple video cards. Just make sure, since you're looking at used systems, that the motherboard actually has any x16 pci-express slots (some motherboards, particularly from oem manufacturers, use integrated graphics and don't have any pci-express slots for discrete video cards).

[melco]

Get MSI 790FX-GD70 MB and cheapest Sempron avaliable for AM3. Should be less than 40$ CPU + <80$ MB

[NetTecture]

Get MSI 790FX-GD70 MB and cheapest Sempron avaliable for AM3. Should be less than 40$ CPU + <80$ MB

Esxact.

Looking for really old stuff has a number of problems:

* Possibly BIOS problems
* Power P4? Remmeber how many watt those used?
* Replacements. You build a minig rig now - you do not want to get crap that breaks tomorrow.

I would go for a nice low power curent solution, and the MSI + Sempron are pretty much the best deal.

[airdata]

I got a sempron 130 last week for $30 on newegg.  I do wonder if this presents a bottleneck when I have 3 cards all mining at one time.

It's also a PITA when I'm having to do anything on the system because the CPU is very slow compared to everything else I have.

[Fakeman]

One downside with the P4 especially is power consumption. If you happen to be sure you will only ever use one GPU, there are some very inexpensive, low power motherboards that come with netbook style processors (Atom D4XX, D5XX, AMD E350) and can be well under $100 for the combo for some of the Atoms. I have a Sapphire E350 (18 W TDP) and it suits me fine for mining with one card, although I didn't buy the mobo for mining specifically. It's not what a lot of people would go for though of course, but I am pretty sure the CPU is not bottlenecking mining performance in any way. Case and PSU were from a crap P4 that idled at 150 W.

[gigabytecoin]

I am running a $25, single cored, AMD 1.8 GHZ Athlon cpu (the 160U).

It only runs at 20 watts, low heat, and I have 6 cards running full speed ahead on them.

[aceman1011]

Sempron 140 is the best CPU. It is decent speed, comes with good quality thermal paste, heatsink, and fan, and is only $40 shipped overnight.

[kjj]

Sempron 140 or Socket 775 Celeron D.

The Sempron has a TDP of 45 watts, while the Celeron is only 35 watts.  However, you can get boards with AM3 sockets that have 6 PCIe slots.  I think if you want that many slots on an intel board, you are looking at a much higher power CPU.

[CubedRoot]

Another vote for a Sempron 140. 

Pick one up at Amazon for $39 bucks with an OEM heatsink and fan:
http://amzn.to/ilK3X3

[Rodyland]

I'm running an Athlon 64 3200+ with my 5770, and the only "problem" I had is that OpenCL isn't supported in Windows XP, so I had to upgrade to Win7.