Hi does anyone know if i can upgrade a mac pro single xeon 5675 to dual xeon 5690

The A1289 2012 Mac Pro was according to EveryMac's chart apparently available as a BTO with 3.06 GHz 6 Core Xeon X5675, though the information I found didn't indicate that was available as a single CPU unit. Not sure about any other model years. Confirmation as to the exact Mac Pro model the OP has is indeed needed.

Regards.

My memory may be faulty, but I seem to remember that the single-processor Mac Pros of that era came with only a single socket, with the space where the other socket would be on the motherboard was just empty. If that's the case, then it would not be possible to upgrade to a dual processor without replacing the motherboard.

Even it there are two sockets, from what I can tell, upgrading the processor in a 2009 Mac Pro at all is possible but it's not simple, and it appears to be quite easy to cause significant failure and appears to require firmware hacking. So it's really not something we can address here in these forums. There are other sites more suitable for this sort of hardware futzing. Though why you'd want to spend probably several hundred dollars (based on the prices I've found on x5690s) on a system that's fifteen years old I don't know.

Regards.

if it left the factory with one socket you would need to replace the slide out processor (single) with a slide-out processor (double). You would also need the TWO heatsinks which are a completely different size and shape from the single heatsink.

There is no extra open socket. and even if there were one, there is no heatsink, and it is not trivial.

also, you can not mix like 2009 model processor modules with the 2010 mainboard, or the reverse. There are chips on the mainboard that are doubled on the processor module (SMC maybe?). if you do not match them, the fans run on high forever.

Single 5690 3.46 MHz hexa-core is as high as you can go with one socket, but with the single processor in a 2009, you can leave the lids in place. Dual-processor that started its life as a 2009 uses rare de-lidded processors, ONLY. 5690 is a Westmere processor, which supports fast RAM speeds, provided ALL RAM is 1333 and not just 1066.

More information needed, please.

the processor you cited does not appear to be standard.

EXACTLY what model-year and what processor did it leave the factory with? What Mac are you starting from ?