HP Prodesk 400 G3 SFF 2nd RAM Slot issue

[GabCK]

Hi!

I wonder if someone could help me please, as I have tried a variety of tests to no avail.

I have a ProDesk 400 G3 (Intel i5 6500) which I am trying to upgrade to use as a dedicated Linux machine. I purchased 2 x 8GB RAM modules (this type; Corsair value select DDR4 2133 15-15-15 as detailed in the maintenance manual).

- When I install BOTH RAM modules (1 in each memory slot), the system refuses to boot, giving 3 long beeps and 2 short ones (memory initialization error)

- When I just put one of the RAM modules into the first memory slot, the system will boot; but this is no good as I need the full 16GB, not 8GB!

- I have tried switching the memory modules and either of them works fine in the first memory slot by itself, but the system just will not boot if I install both modules

- I assumed that the mainboard was faulty, so purchased a new mainboard. The same problem is happening with the new mainboard.

Given all of the above, the only rational conclusion I can come to is that the processor or motherboard just doesn't like the memory modules; but they are exactly the same spec as the HP ones and the manual does say that "industry standard" DDR4, 2133 modules with 15-15-15 timing are ok.

Has anyone else experienced this and if so, what did you do to fix it?

Thanks in advance

Gabriel

[itsmyname]

@GabCK -- how many memory chips per side of the original stick of RAM? Capacity -- 4 GB? 8 GB? 

How many memory chips per side of the replacement stick of RAM? 8 GB per stick? 

Is this your motherboard: HP ProDesk 400 G3 Desktop Mini Business PC Product Specifications | HP® Customer Support

It should support up to 32 GB of DDR4 RAM.

[GabCK]

Hi @Itsmyname and thank you for replying.

I can confirm, that the motherboard in that document is the same one that is in this machine. Both the motherboards (the original and the replacement one I bought when I assumed the motherboard was at fault, are the same type, part number etc. The only difference is that one is revision 0C and the other revision 0G.

I don't have the original RAM. The machine was without RAM when I bought it. There was just the processor (i5-6500). The previous owner had one (1) 8GB stick of memory in the machine but didn't sell the machine with the RAM as he needed it for his new PC. I saw the machine working before paying for it, at which point he removed the single 8GB stick of memory from the machine, hence me buying new RAM for it.

The Corsair memory I bought for it has 8 RAM chips per side for a total of 16 RAM chips per stick.

Noteworthy:

- I have used anti-static precautions (ground strap and grounded work area) and tested both the CPU and the RAM in another machine. All are working....just....not together in the Prodesk 400

- I was going through all the specs for the Prodesk 400, the CPU and the RAM again (for the hundredth time) and I had a "uh-oh" moment, though I don't know how big of a one (yet)... I noticed that the CPU is the i5-6500, NOT the i5-6500T as specified in the maintenance manual. Surely this shouldn't make a difference to the RAM though, given both the 6500 and 6500T support more than 16GB RAM and both have dual channel memory capability...)

Cheers

Gabriel

[itsmyname]

@GabCK -- the web-site at www.crucial.com has an interactive part that can tell you exactly which sticks of (made-by-Crucial) RAM are guaranteed to be compatible with your motherboard.  Hopefully, the specifications for their sticks match the specifications of your new RAM.  Worth a try!

[GabCK]

@Itsmyname I checked the Crucial website and none of the modules it suggests are compatible (according to the 400 G3's maintenance and service manual). The manual says that the motherboard & chipset support up to 32GB of PC4-17000 RAM, with 15-15-15 CAS timing; but none of the Crucial parts suggested by the interactive tool comply with that timing or speed.

However, the Corsair RAM I have does comply exactly with the service manuals requirements...

In fact the only part that doesn't meet the requirements in the manual is the processor, which is an i5-6500 and not the 6500T

Even though - by rights - the RAM I have should work with the chipset (verified to work with the Intel 100 series chipsets) and the Processor (according to the i5-6500's Intel ARK entry), I think it's reasonable to assume that something in the combination of the non-standard processor and using 2 X 8GB RAM sticks is causing a hiccup.

Again, it works fine with just the one stick of RAM, but wont work with two. So the memory is good (and compatible), the motherboard is good (I now have a spare, if anyone needs one?!) and the processor is good but I guess not compatible, even if it will work with just one stick of memory.

It's quite irritating really, but I guess there were good reasons for only including the i5-6500T and not the i5-6500 in the compatibility list. I will admit though to scratching my head as to why that might be, because as far as I can tell, the 6500 doesn't exceed the power or clock of the i7-6700 which is compatible with the machine....in fact, side by side, there is only a difference in clock speed and power; all the other capabilities and architecture are the same. The 6500T is a 35W CPU and the 6500 is a 65W one (the same as the i7-6700 that the machine can use)...

I'll dig a little more into it and see what real differences - beyond the obvious - there are between the 6500 and 6500T; it's piqued my curiosity now...