latest version of the mod as of yesterday. We have a moderate setup, probably a couple hundred wires and half a dozen storages linked up but lately we've been getting some bad graphical lag. F3 showing hundreds of updates, after much trouble shooting we finally removed the cable master and suddenly all the lag was gone. So it would appear that once you start getting into a decent sized setup you run into pretty extreme fps loss. Was hitting as low as 10fps at times on a high end gaming pc.

Optifine seemed to help immensely once I added that in for what it's worth.

can you give me the world save?

It's on a sever I'll talk to the owner about it this evening

So I tested this on my side with some "very" complicated network in both 1.8 and 1.8.1
Did not tried smp but I doubt this will make a difference in this case.
Of course fps drop is expected with that amount of connected TileEntities - don't know if @MrRiegel is using ISBMs or FastTESRs or other special case renderers but it is expected. In my case FPS drops from 120 to around 40-45 and my processor isn't that high end anymore.
I did not notice any difference between those two version
There was also no difference if network had cable master or not, same for moving items or not.
There was short lag on first connection with CM. Other than that
Stats;

• 1200 grey network cables
• 240 storage cables connected to
• the same amount of chests
• 90 import cables connected to
• 90 chests that are connected to another
• 90 storage ones that are connected to
  -3 super fast import cables sucking cobble in order to saturate whole network.
  The power usage is way higher than CM can handle hehe.
  Pretty picture of my setup:
  
  

BTW I do not recommend this kind of networks other than a test env as apparently it is too much data for MC Anvil engine;

[File IO Thread/ERROR]: Failed to save chunk
java.io.UTFDataFormatException: encoded string too long: 98113 bytes
    at java.io.DataOutputStream.writeUTF(Unknown Source) ~[?:1.8.0_74]
    at java.io.DataOutputStream.writeUTF(Unknown Source) ~[?:1.8.0_74]
    at net.minecraft.nbt.NBTTagString.func_74734_a(NBTTagString.java:28) ~[ea.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:392) ~[dn.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:24) ~[dn.class:?]
    at net.minecraft.nbt.NBTTagList.func_74734_a(SourceFile:45) ~[du.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:392) ~[dn.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:24) ~[dn.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:392) ~[dn.class:?]
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:24) ~[dn.class:?]
    at net.minecraft.nbt.CompressedStreamTools.func_150663_a(CompressedStreamTools.java:111) ~[dx.class:?]
    at net.minecraft.nbt.CompressedStreamTools.func_74800_a(CompressedStreamTools.java:101) ~[dx.class:?]
    at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_183013_b(AnvilChunkLoader.java:232) ~[anj.class:?]
    at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75814_c(AnvilChunkLoader.java:210) [anj.class:?]
    at net.minecraft.world.storage.ThreadedFileIOBase.func_75736_b(SourceFile:37) [auc.class:?]
    at net.minecraft.world.storage.ThreadedFileIOBase.run(SourceFile:30) [auc.class:?]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_74]

I don't think it's the fault of the cables.
@Saereth wrote, that the problem was gone by breaking the cable master.

yes, it always wasnt anywhere near that many, 300 cables tops, 3 request tables, 1 master. They were connected to storage drawer controllers (2) and 3 modular storage systems from rftools if that makes any difference. I havent heard from the server owner about a world save yet.

@MrRiegel, saving chunk failure ? Pretty sure mc is unable to save chunk with cable master that is connected to that big network ^^ - ripping part of this monster helps :).

Ok, I hooked a bunch of rf modular storage blocks filled with stuff plus a bunch of storage drawers controllers with few drawers each - that did not change much in frames.
The only thing that causes more drops ( because of chunk redraws ) is Indicator block if I hook it additionally and it is not constant drop, more like every half a second. Plus in this case it cost me like 4ms of TPS.
It is worth to mention that I did not set anykind of filters in cables.

I made a setup with 463 storage cables and 463 chests.
the cable master saves 28826 bytes. (positions of cables and inventories).
a cable saves max. 1358 bytes.
1358*463=628754
thats way more than the cables master.