How much do iGPUs degrade CPU performance?

[LloydLynx]

So I know that iGPUs can suck up memory bandwidth and reduce CPU performance, but how significant is that performance loss? I have this Core 2 Quad dual channel memory system running a small Minecraft server, and I value CPU performance most, going as far as to not use a graphical environment in Linux. On these old systems the north and south bridge are located off the CPU and I think they manage both memory and PCIe lanes, so I'm not sure if I would get the same benefit as a more modern CPU by eliminating the iGPU from usage. My question is: If I throw in some cheap PCIe card off ebay or something, how much performance gains will I get with the CPU? Anything significant enough to warrant $10? Will the GPU specs affect anything on the CPU?

[Mister Woof]

iirc GPU is on the motherboard on those systems.

[vanished]

I honestly hadn't ever even considered this or heard of it being mentioned before.  I thought this was going to be about a laptop where there's a power limit and in that case, having the iGPU suck some up can definitely lower performance for the CPU, but I'm not sure how much of an impact it would have here.  I'm going to try running some tests.  In the mean time I will just say that I know "last gen" iGPU systems, like what there was on Core 2 systems and earlier were typically very low powered and temperamental.  We take for granted these days that an iGPU will basically run anything the same as a modern dGPU, albeit at much lower framerate, but it definitely was not always the case.

[Bitter]

Yes, on Intel systems prior to Socket 1156/First gen Core iX systems the integrated graphics are part of the motherboard and other than consuming some system memory do not affect CPU performance in any measurable manner. Some boards didn't even have on board graphics, mostly the higher end boards where that would be unused so it was never installed. You can get a cheapo card for simple display out duties if you desire, $20 gets you a Radeon HD 7570 or 6570 which is PLENTY for simple display out and can actually handle casual office work and basic internet use as well if needed.

[Metallus97]

IT DOOOOES! 

I have a MBP 2018 with a i5 8259U. When using the CPU and not much of the iGPU, the CPU boosts to full speed. But when taxing iGPU and CPU, the CPU won't boost. This is due to power limits and temperature limits. Or weeeeeelll the mhhheee cooling on those machines