How are you getting higher density? Are you going to run more than 3 of them in 1 rig? are you going to run them in a rack? If not then get 6x7950/7970s and have the same density. The only density that matters is mh/rig, mh/card is irrelevant.

For every 7990 you buy you could have had 3.5-4x7950s depending on at what price you can find them, how does it make any sense to pick the 7990. Even counting the extra motherboard requirements etc you would still be looking at 3x7950 vs 1x7990 price wise. Justify that please, all I get when I have asked is "it's my money and I can do what I want"
 

Speed up the work? There won't be any chips until mid-end-June, except maybe for testing samples.

unexpected problem..
Guiminer 0 shares accepted
Runs about 591kh/s but 0 shares accepted after some time. Trying to mine LTC in coinotron,notroll.in

using
Windows 7
12.8 catalyst drivers
AMD-APP-SDK-v2.4-Windows-32

, with guiminer settings 7950 high usage mining doesn't work,

SI Prefixes
Multiple   Prefix   Symbol   Example
1,000,000,000,000,000,000 (1018)   exa-   E   Eg (exagram)
1,000,000,000,000,000 (1015)   peta-   P   PJ (petajoule)
1,000,000,000,000 (1012)   tera-   T   TV (teravolt)
1,000,000,000 (109)   giga-   G   GW (gigawatt)
1,000,000 (106)   mega-   M   MHz (megahertz)
1,000 (103)   kilo-   k   kg (kilogram)
100 (102)   hecto-   h   hm (hectometer)
10 (101)   deka-   da   daN (dekanewton)
1/10 (10–1)   deci-   d   dC (decicoulomb)
1/100 (10–2)   centi-   c   cm (centimeter)
1/1,000 (10–3)   milli-   m   mm (millimeter)
1/1,000,000 (10–6)   micro-   (   (F (microfarad)
1/1,000,000,000 (10–9)   nano-   n   nm (nanometer)
1/1,000,000,000,000 (10–12)   pico-   p   ps (picosecond)
1/1,000,000,000,000,000 (10–15)   femto-   f   frad (femtoradian)
1/1,000,000,000,000,000,000 (10–18)   atto-   a   aT (attotesla)



When will we reach 1 Exa Hash per second?  EH/s <---- Eh? Canadian named it.