I have 2x2GB memory in my 2 (of 3) blue slots (Hynix 2GB 2Rx8 PC3-8500E-7-10-E0 ). Everything works fine. I wanted to upgrade to 12 GB and purchased (on eBay) 4x 2GB Dimms (Hynix 2GB 1Rx4 PC3-8500R-7-10-C1). When adding the memory the system won't boot, fans are going on max and screen stays black (no beeping). I tested with just 2 new ones and I get a (memory failure?) beep code 1-3-3-1. In different combination of 2 new dimms in blue slots I get no beeping at all. I updated to latest bios and no difference in behavior. So my questions are:
1. Can I use single rank dimms in S20?
2. Can I mix single rank vs dual rank?
3. Is the new memory broken?
4. On the memory there is a second sticker showing some Sun part number (Sun (TM) 371-4426-01). Is this memory more than just a rebranded standard Dimm. Can It be some kind of SUN only memory, like Sun used special firmware on harddisks and other (generic) parts?
unfortunately you purchased the wrong type of memory. the new modules are RDIMMs and not supported in your system. you need ECC UDIMMs instead.
mixing ranks isn't the issue. the PC3-8500E vs. PC3-8500R is where things went wrong. you need PC3-8500E or PC3-10600E modules. the 'E' means it's an ECC Unbuffered DIMM (or UDIMM) where the 'R' means it's an ECC Registered DIMM (or RDIMM).
hopefully you can return the modules to the reseller and source something else.