Is it possible to add another cpu with a custom PCI card?

[Ticker305]

I keep hearing how GPU's are really like another computer in your computer and acts a lot like your cpu. So that got me thinking, why hasn't anyone invented a pci card with a cpu socket on it that can be added to your current processor sort of like SLI or Crossfire. That would open up a ton of headroom for upgrades and extend the amount of time we could use a certain chipset before it becomes a dead end.

I'm sure this has been asked or thought of before, but in all of my years of lurking I have never seen anyone inquire about this. Is there some sort of fundamental reason why it hasn't been done, or is upgrading just half the fun and the thought of staying with the same board for more then 4 years a scarier thought then marriage?

 

[Forceman]

Bandwidth is probably a big one. Even the PCIe bus is terribly slow compared to the memory bus. That and having software that can support multiple CPUs - the home versions of Windows don't, for example. They did sell add-in co-processor cards back in the day though, if I remember correctly.

 

[tacohunter52]

I don't know if this will happen if the way you're meaning, but you just reminded me of those old cartridge CPUs. That was kind of like putting the CPU in a PCIe slot lol.

 

[Tsuyoi]

The problem with this is that the existing CPU would also have to be designed to support Multi-CPUs, and there would be zero backwards compatibility. The OS would also have to be able to support this. Ultimately though, the PCIe slot just wouldn't be able to put out the required speeds to keep up with the central CPU, not to mention you would have to mound a HSF horizontally to cool the secondary CPU, which would require a massively extended MoBo. So however you look at it, it's simply impractical (it'd be like trying to make a 5 wheeled bike)