Can I connect an 8800 640mb gts with an 8800 320mb in SLI?

Hi,

I was thinking of going sli and while looking at the prices saw that the 8800 320mb gts is cheaper than the 8800 640mb gts. Can I hook these two up in SLI? Will that work or do they have to be exactly the same?

Thanks

Here they are:

8800 320mb gts:

http://www.newegg.com/Product/Prod [...] 6814130082

8800 640mb gts:

http://www.newegg.com/Product/Prod [...] 6814130327

to rayn:
http://www.tomshardware.co.uk/foru [...] sfire-faqs

Do the cards have to be same model?
I answer it with an example:
You have a NVIDIA Geforce 7800GTX 256, and you want to add another card , the second card has to be 7800GTX exactly.

But what about the memory? Can you add a 7800GTX 512 and use that with 7800GTX 256?
It's recommended to use a 7800GTX 256 with a 7800GTX 256 and 7800GTX 512 with 7800GTX 512.
However you can use a 7800GTX 256 with 7800GTX 512 , BUT the 7800GTX 512 will lower its clock to operate with the 256 one , so it wont have its true power. (This option isn't recommended )