Windows 7: Windows File Sharing: Slow transfer speed when CPU is 100%

Hello. I will try to explain the issue as simple as possible.
I have created a Gigabit LAN network with 2 home PCs, where:



PC1 = Machine for video rendering. Motherboard: ASUS P8P67 Pro; NIC: Intel 82579V.
PC2 = Machine for work and a Data server for PC1. MB: Gigabyte EX58-UD3R; NIC: Realtek 8111D.
Router that bridges the computers: TP-LINK TL-WR1043ND, latest firmware.

Drivers for both PCs are the latest from Intel's or Realtek's websites.

I use PC1 for rendering/compression the files that are created on PC2, I have shared (through Windows' native file sharing/Samba) the PC2's entire hard drive and I load the project files on PC1 without copying to its hard drive.

If PC1 is idle, the compression on PC2 goes flawless and CPU is always at 100%.

However, if I put some stress on PC1 (compression for example), the transfer speed slows down and the compression slows down as well as pointed on this screenshot:




Both computers are using Windows 7 SP1 x64 Ultimate with the latest updates installed. No antivirus software or firewall installed.


I am open to ideas, solutions and alternatives.

Thank you in advance.