Not sure on the answer to your second question but I don't think there's anything too odd about this difference..the limit seems to vary between 1.4 & 1.7 as I said before.
Regarding your former post, note that you don't necessarily need to abandon 32 bit plugs if you still use a 32 bit host in your 64 bit o/s...that should still let you use up to 4Gb just for Nebula.
Your Q6600 would probably work pretty well if you up your ram but you said you were on 60% cpu already & an i7 would give you the extra grunt you might need if you start using some of the heavy 3rd party programs.
I'm pretty much set up to test my new i7 system now so hope to be able to post some figures on how this is working for me soon....I've stayed with 32 bit host as I use Duende a lot which doesn't support 64 bit yet. Going to try 32bit Neb with no bridging first & then with jbridge & if still not happy will try bridging to 64bit Nebula.
OK....First test results...possibly the last as I'm surprised how good these are & as I pre render my inputs & tapes this would be enough Nebs for me.
Hope this is useful info for someone.
Intel i7 930 @ 2.8 with 12Gb Ram. 9500GT graphics but no CUDA. (Put together by Scan computers in UK). Win7 home premium 64bit Cubase 5.1. TC Konnekt 24D f/w at 1024 samples. Nebula 32 bit. No bridging just straight install.
Nebula Reverb tweaked to DSP Buffer 2048 for less latency (so more cpu used) Rate CNV is at 3496.
Programs: AlexB CLC mic in (Unfortunately waiting on a new authorisation for my MBCPro) R2R Studer Tape Boost plus TapeSat 1/4 db CLC Buss Group Clean Doc Fear Combo EQ
No other plugs or VSTi...all tracks 24 bit stereo audio at 44.1k.
I inserted all 5 plugs on channel 1 of a 20 track project & copied them to each channel until I maxed out. Checked playback & stop while taking CPU reading from Windows Task Manager.
10 channels, 50 instances everything is smooth with Ram use at 3.66Gb & CPU peaking at 89%. DAW response still very good.
11 Channels, 55 instances slightly slower loading of plugs but still running fine at 3.87Gb & CPU peaking at 92%. DAW respons surprisingly still very good.
12 channels, 58 instances, 3.97Gb & CPU peaking at 98%. I'd cartainly avoid this sort of loading in a real project, but amazingly it still worked very well except for a very slightly slower response to controls.
12 channels, 60 instances 4.1Gb & CPU now hitting 100% & causing drop outs, Cubase still surprisingly well behaved, no crash or GUI problems....really surprised this can work at all!
After saving the song with the safe 55 instance reload time was a fairly painless 95 seconds.
To put these figures into perspective Cubase is notoriously resource hungry & on my Q6600 & 32bit XP I've never managed to open more than about 10 of these programs in a project. Other host (Reaper) would probably do better.
I'm well chuffed...thought I'd be messing about with bridging & tweaking settings for weeks to get results like this