HP ProLiant BIOS – 8GB Memory Detected but Only 4GB Shown in POST

Just ran into the same problem with an R310. Took quite a bit of digging but the link to the R310 Tech Guide helped. The 1GB UDIMM uses 128Mb x8 chips which is why it works. The Samsung sticks they keep sending you use 256Mb x8 chips and as you found in the Tech Guide the R310 won't work with 256Mb chips. I ran into the same problem using some memory we pulled out of an R710 server but they were 256Mb x4 chips so it was a double no-no.

Here is what I've found regarding memory. The actual DRAM chips on the memory module have differing numbers of lines. This is also referred to as the rank width, e.g., x4, x8, x16. The DRAM chips are also different sizes, e.g., 128Mb, 256Mb, 512Mb. The easiest way to explain ranks is to think of each rank as a virtual DIMM. So a single rank module is just that; a single memory module on a single physical DIMM. Dual rank memory actually has 2 memory modules on a single physical DIMM (it's deeper than that but this is the easiest way to visualize it).

So the bottom line is that the R310 will only accept DIMMs that are made out of 128Mbit or 1Gb/2Gb chips that are x8 devices. Or at least that's my story and I'm sticking with it until Dell tells me otherwise; e-mail to them is out and I'll let you know if they say something different.

Link to Hynix part: http://www.hynix.co.kr/datasheet/eng/module/details/module_20_HMT112U7BFR8C.jsp?searchType=2&menuNo=1&m=1&s=1&RK=20&RAM_NAME=

A link to an excellent briefing from Intel: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDsQFjAB&url=http%3A%2F%2Fdownload.intel.com%2Feducation%2Fhighered%2Fsignal%2FELCT865%2FClass2_21_lab_and_project_assignment3.ppt&ei=VKOiT-yKDoau9AS86730CA&usg=AFQjCNHOMlxRyI0C8F7GIdwMkU8h1ZOmyQ&sig2=nLNmplaHcJjbv7rktoqb2Q

Slide 13 is the key, but the entire package is very good depending on your level of geekdom :)

Update: Confirmed with Dell except that I was wrong about requiring 128Mb and smaller chips. The Foxhollow platform does support 1Gb and 2Gb chips. See here: http://cache-www.intel.com/cd/00/00/43/26/432686_432686.pdf

TL;DR - it's the MiniSAS

First things I tried was basic troubleshooting - different VGA cable, different power cable. No luck there so I tried with the original RAM - still no progress.

I logged a job with HP who diagnosed a motherboard fault and sent out a replacement board. After swapping the boards over I started the machine up with video and a blue (good) status light but realised the MiniSAS cable wasn't plugged in and once I did the machine refused to boot.

I was sent a new MiniSAS cable and managed to replace it - not an easy job. The server booted and is now working as expected.

If you have this issue, try unplugging the MiniSAS and see if the system boots. If it doesn't, contact HP or find a supplier for a HP Part Number: 616572-001 or HP Spare number 624881-001. The cable looks like this:

I had difficulty finding instructions to replace the cable so here is how I did it. HP also provide an instruction video here.

To remove the MiniSAS cable you will need to remove the MiniSAS from the motherboard (can be difficult) and for ease of access remove the motherboard and tray, and the 4x Hard disk caddies. You will then need to remove 4 screws at the back of the chassis. The allen key that comes with the machine and should be stored in the door can be used for this. The locations are marked below.

Once the four screws are removed the MiniSAS cable needs to be fed back though the chassis, over the power supply, but you will need to cut a number of cable ties to do this. Then you will need to disconnect the 4 Molex connectors (if you have a hard disk or CD/DVD drive in the top bay this will need to be removed to gain access to the cables). This was not easy as 1 of the cables was very stiff and needed some coaxing to come out.

Once the screws and cables are loose the rear panel that was unscrewed can be removed - I had to bring it forward feeding the cables down behind it and then rotate it so it could slip out between a center stand in the disk caddy area. You then end up with this (actually upside-down here).

The cable can then be disconnected from the mounting plate - 8 screws can be removed using the tool that comes with the server. The replacement cable can be pushed into place (small plastic bumps line up with holes in the rear and then screwed in. The plate can be put back into place, feeding the cables up past the fan, and then screwing back into place. Molex cables need to be connected back up, the MiniSAS fed back through over the PSU. Motherboard can be put back into place and MiniSAS, Power and other connectors can be done as well.

Put the door back on, cover on, power in and VGA in and start it up. That should be it.

Good luck.