DDR3L RAM in DDR3 Slots? Mix DDR3L and DDR3?

SkunkWorksSR71

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Jun 4, 2017
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I'm upgrading an Optiplex 9020 SSF (i5-4590 non-K) and according to the Dell website:
"Note: DDR3 and DDR3L
DDR3 and DDR3L are socket compatible, however, It is NOT compatible with systems using 4th Generation Intel (Haswell) processors, which exclusively support 1.35V operation for memory.
OptiPlex 9020 (MT, SFF) 4 32Gb 1600MHz (DDR3 Non ECC)
"
http://www.dell.com/support/article/us/en/19/SLN152123/optiplex--memory-compatibility-guide?lang=EN

However, the current RAM in the system is DDR3 (Hynix 4Gb HMT451U6BFR8C) even though I'm using a Haswell cpu. While I suppose the first question is whether the slot on my motherboard is actually DDR3 or DDR3L, my other questions are:

- If it is a DDR3 slot, can I use DDR3L ram?
- If I buy DDR3L ram can I still use my existing DDR3 ram?

Thanks!