Hi there!
I am experiencing the same problem in Cubase 5.5.3. I’ve been using Cubase 5.5 for a few years now with Windows XP SP3 x86 without any problems (with a EMU 1820m PCI audio setup). I recently upgraded my DAW with a MR816 and thought, hey… Let’s upgrade to Windows 7 x64 while I’m at it… NOT… I found out that complex projects with over 24 audio tracks with heavy duty VST’s run smoother in XP x86 in comparison to Windows 7 x64 (and yes, all VST’s are x64 as well). The Windows 7 x64 configuration is very basic and no special hardware is installed. I also optimized everything in Windows 7 (disabled aero, disabled ntfs encryption, disabled executable swapping, gave background processor priority, disabled indexing, no WLAN, set power management to performance, disabled Cool 'n Quiet).
I am currently investigating the PCI firewire card in combination with PCI latency issues (amongst other things the BIOS PCI latency setting). Fiddling around with this setting in the BIOS does have effect, but still the x86 environment runs smoother.
I have ordered a special firewire PCIe card with a TI (Texas Instruments) chipset and will exchange my old VIA PCI firewire card with this PCIe card and see if that helps. I suspect that this will make some difference being that a PCI card runs at 33mhz with a top bus speed of 133 MB/sec half duplex in comparison to 1x (1 lane) PCIe at 100mhz with a bandwidth of 400 MB/sec full duplex. Needless to say there will be some latency improvements.
Analyzing CPU while running these major projects also lead me to the conclusion that there must be some bus limitation/ latency issue. While running these projects the CPU almost never peaks over 40% (all cores). Due to the amount of memory HDD activity is nearly 0 while running the project.
I will keep you posted regarding the results.
PS. My setup is:
AMD Phenom II 1090T 6-core running at 3.6 Ghz
Asus M3A motherboard
6 GB RAM DDR2
2 TB WD SATAIII 7200rpm HDD
NVidia Geforce 8600GT PCIe
VIA chipset Firewire card (s400)
MR816X with ADA8000 through ADAT
Yamaha Motif XS8 daisy chained to MR816X
Yamaha MO8 & Roland TD-10
Kind regards,
WizzyWizz