DDR2 woes on HP DC7800

Question

My desktop (HP dc7800) has two 1GB DDR3 modules in it, and slot for 2 more. I tried to add (working) 2x1GB sticks of DDR2, 667, PC5300U. But got angry beeps and no boot. Any ideas?

Current memory:

 *-memory:0
      description: System Memory
      physical id: 33
      slot: System board or motherboard
    *-bank:0
         description: DIMM DDR2 Synchronous 667 MHz (1.5 ns)
         product: 8HTF12864AY-667E1
         vendor: JEDEC ID:2C 00 00 00 00 00 00 00
         physical id: 0
         serial: 4E351FDD
         slot: XMM1
         size: 1GiB
         width: 64 bits
         clock: 667MHz (1.5ns)
    *-bank:1
         description: DIMM DDR2 Synchronous [empty]
         vendor: JEDEC ID:
         physical id: 1
         slot: XMM2
    *-bank:2
         description: DIMM DDR2 Synchronous 667 MHz (1.5 ns)
         product: 8HTF12864AY-667E1
         vendor: JEDEC ID:2C 00 00 00 00 00 00 00
         physical id: 2
         serial: 4D351FDD
         slot: XMM3
         size: 1GiB
         width: 64 bits
         clock: 667MHz (1.5ns)
    *-bank:3
         description: DIMM DDR2 Synchronous [empty]
         vendor: JEDEC ID:
         physical id: 3
         slot: XMM4

Answer 1

HP clearly indicates that this model can support 4gb of Ram @ 4x1gb configuration. Configurable Components. The speed and size of the Ram you indicate falls well within the parameters set by HP. I realize I am most likely telling you nothing that you did not already know. I am just being clear that you haven't done anything wrong by accident... from what information you have provided.

What could be wrong? For one, you might be mistaken about the two sticks that you want to add, in that they might not actually be working. You could try replacing the existing memory with those two sticks (instead of adding them) and see if the machine boots. By Replace, I don't mean put them in the empty slots, and then remove the old ones. The black slot has to always have a Ram stick in it, so I mean actually put the two new ones in the same slots that the old ones were in. If the machine boots without beeping angrily at you, then you have confirmed the Ram is not what is making it beep.

It is possible (but not probable) that when you put the new Ram in, you didn't seat one or both sticks completely. I realize you most likely checked that, which is why I say it isn't probable. I just have to mention the possibility.

I can tell you that it does NOT have to do with the fact that the new Ram is pc2-5300u Ram. The U means unbuffered, and the Ram already in the unit is ALSO unbuffered.

So, confirm that the new Ram is indeed good Ram. If you just bought it, that is no guarantee.