Mac Pro 4,1 upgraded or 5,1?

[ALim]

I'm looking to buy a secondary machine I can either offload rendering to and/or use as a primary station in it's own right for a while and would like to get a 5,1 but there's not too many floating it around it seems, though a fair few upgraded 4,1 s. My question is it worth continuing to scour for a clean 5,1 and are there any major/specific advantages over getting say a 12 core 3.46 2009?
I'd prefer to buy as clean as possible with not too many mods. Is ebay THE place to look or any other good resources. Either US or UK.
Thanks

 

[KeesMacPro]

The Mac Pro 4,1 and 5,1 are technically the same and can be upgraded equally .
The only differences are :
- the LogicBoard and Processorboard of a 4,1 and a 5,1 can not be exchanged because of a different SMC number.
-the 4,1 DUAL processor uses delidded CPUs, while the single CPU and both 5,1 single and dual CPU use normal lidded CPUs.

 

[ALim]

The Mac Pro 4,1 and 5,1 are technically the same and can be upgraded equally .
The only differences are :
- the LogicBoard and Processorboard of a 4,1 and a 5,1 can not be exchanged because of a different SMC number.
-the 4,1 DUAL processor uses delidded CPUs, while the single CPU and both 5,1 single and dual CPU use normal lidded CPUs.

Great thanks. I've seem some stuff about delidding the CPUs but was still trying to work out exactly why it's needed. To create space am I correct?

 

[KeesMacPro]

YW.
I could only speculate about why Apple decided to construct de 4,1 DUAL with delidded CPUs..

 

[RAMtheSSD]

I have upgraded my cpus a couple of times now --I want to have all the bugs worked out for the 5690s-- and it seemed impossibly hard before I knew how but (I will update when I find the info on the "pad" material that is needed for the little chips around the heat exchanger) anticlimactically simple once I knew about the washers. I took a risk and bothered a lot of people trying to figure it all out on my own but there is a mom and pop computer shop (out of WA I think) that sells a kit so the guesswork is taken out of the equation. All that is left is cross tightening the heat exchangers back on very carefully (try with 5620 or something equally inexpensive to get a feel for it before you go for the 56(70,80,90)s.

One thing I will absolutely say, get the two cpu machine. The difference in max ram is serious and an X5690 is crazy fast in comparison to the WXXXX that can be installed in the single CPU machine. You do not need to do the pixlas mod right off if you don't want to but you will want to upgrade the wifi/bluetooth card and replace the Northbridge plastic screws with stainless steel (there are kits and there is a lot of discussion about this topic) because you will have everything as accessible as it can possibly be anyway.

Delidding is more of a heat transfer thing but I imagine that the surprise was that the transfer efficiency just wasn't there because the lid is larger than the processor by enough to matter. Also, the lid is fastened to the processor by someone who has done it a million times so the conductive paste --even if their paste is nowhere in the league of the current DIY stuff-- is applied perfectly enough that the heat transfer rate is perfect. Somewhere in the process, Apple probably found that the "we made a million, how many do you want?" processors are cheaper to source than the "you want what?!" kind.