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RDRAM working, but only two sticks show up

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December 5, 2008 1:43:35 AM

I've recently installed two additional sticks of Rambus PC800-40 in a Dell Dimension I'm working on. It came with 128x2, and I put those in the second pair of memory slots and installed 256x2 in the primary pair of slots. The computer runs alot faster, programs load in seconds compared to up to a minute before the upgrade, and all four sticks show up in SiSoftware Sandra, and it shows that are all working properly.

However, when I right-click My Computer, with 768MB installed, it says I have 256MB of RAM installed. When I take out the 128x2 in the second pair of slots and put in the dummy sticks, it displays 448MB in My Computer and 512MB in Sandra. Any ideas what's going on?
December 5, 2008 1:53:11 AM

I can't say why your computer won't see the whole 768MB. But the reason why it only says 448 when you have 512MB is because some of the memory is taken for the onboard video memory.
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a c 78 } Memory
December 5, 2008 1:58:32 AM

Do you have an on-board video controller? Do the new memory modules have identical specs to the original ones? Are they on the list of compatible modules?
December 5, 2008 2:05:48 AM

Rambus can be very finicky about mixing and matching (speaking from experience, I still have a machine here running with 1GB RDRAM, I hate Rambus).
December 5, 2008 2:09:19 AM

GhislainG said:
Do you have an on-board video controller? Do the new memory modules have identical specs to the original ones? Are they on the list of compatible modules?

The computer has a video card installed in the AGP slot on the motherboard. There's no video integrated onto the motherboard.

The specs/labels on the two RDRAM sticks, exactly as they appear:
Stick 1 256:
Quote:
Samsung Korea 0307H 256MB / 8
MR16R1628DF0-CT9 1066-32P 102

Stick 2 256:
Quote:
Samsung Korea 0244 H 256MB/8 ECC
MR18R1628AF0-CM8 800-40 101

Stick 3 & 4 128:
Quote:
Samsung Korea 0244 H 256MB/8 ECC
MR18R1624DF0-CM8 800-40 012

Again, Sandra reads them all and reports no problems. It lists them all as having identical specs, despite one of the 256MB sticks being 1066-32P. The 2x256s just aren't showing up on My Computer properties, just the 2x128s when both pairs are installed.
December 5, 2008 2:11:22 AM

The fact it's running RDRAM, I wouldn't invest a lot of time or money into getting it up and running. That system is at least 6 years old. I throw out any RDRAM system I come in contact with that isn't running because of how expensive the RAM still is.
a b } Memory
December 5, 2008 2:13:09 AM

The difference between 448 and 512 could be due to an onboard graphic controller. My memory could be faulty but I remember that Rambus didn’t support more than three sticks of ram due to timing issues, so that should be three sticks of ram and one dummy.

December 5, 2008 2:22:43 AM

pjmelect said:
The difference between 448 and 512 could be due to an onboard graphic controller. My memory could be faulty but I remember that Rambus didn’t support more than three sticks of ram due to timing issues, so that should be three sticks of ram and one dummy.



No, RAMBUS has to be installed in sets of two, and any remaining slots must be populated by continuity chips (CIMMs). So it's either 2 or 4 actual RIMMs.
December 5, 2008 2:24:31 AM

runswindows95 said:
The fact it's running RDRAM, I wouldn't invest a lot of time or money into getting it up and running. That system is at least 6 years old. I throw out any RDRAM system I come in contact with that isn't running because of how expensive the RAM still is.

I only spent $20 on the 2x256 I listed, so I'm not breaking the bank or anything. It's my mom's computer, and I'm limiting the upgrades to the memory I bought, a 7200RPM hard drive to replace the 5400RPM one, and a 2.66GHz P4 to replace the 2.4GHz P4, that last two I just have sitting around and no use for otherwise.
a c 78 } Memory
December 5, 2008 2:29:07 AM

Your problem is with the 256MB stick that has the label

Samsung Korea 0307H 256MB / 8
MR16R1628DF0-CT9 1066-32P 102

This one isn't ECC (only 16 chips instead of 18). It also is 1066Mhz instead of 800Mhz and 32ns instead of 40ns. That explains the weird memory issues that you have. Replace it with another one like stick 2 and you'll be fine.
December 5, 2008 2:31:20 AM

GhislainG said:
Your problem is with the 256MB stick that has the label

Samsung Korea 0307H 256MB / 8
MR16R1628DF0-CT9 1066-32P 102

This one isn't ECC (only 16 chips instead of 18). It also is 1066Mhz instead of 800Mhz and 32ns instead of 40ns. That explains the weird memory issues that you have. Replace it with another one like stick 2 and you'll be fine.

Even with My Computer properties only reading the 2x128MB sticks, I instantly noticed a massive increase in the computer's performance after installed the 2x256. So I'm guessing everything's working, but it's just not being listed on the XP OS My Computer specs? Is it just some kind of harmless quirk caused by one of the sticks being 1066?
a c 78 } Memory
December 5, 2008 2:38:35 AM

You normally can't run 2 RDRAM sticks that are that different without running into issues. If both were ECC, it would probably work even though one is 1066, but you have one that's not ECC. If you leave it like that, run memtest for several passes to ensure that it's stable. When the OS doesn't see the correct amount of memory, it usually is an indicator that something is wrong.
December 5, 2008 2:53:31 AM

GhislainG said:
Your problem is with the 256MB stick that has the label

Samsung Korea 0307H 256MB / 8
MR16R1628DF0-CT9 1066-32P 102

This one isn't ECC (only 16 chips instead of 18). It also is 1066Mhz instead of 800Mhz and 32ns instead of 40ns. That explains the weird memory issues that you have. Replace it with another one like stick 2 and you'll be fine.



Good catch Ghi! I totally missed that.

Yea, running ECC and non-ECC is a :non: 
December 7, 2008 12:52:17 AM

I listed the PC1066 non-ECC on eBay for $28 and sold it right away. So I made a couple bucks on that chip over the $20 I paid for both. I purchased a couple 256MB PC800-40 non-ECC and the computer's running with 768MB and it's all being read correctly by the computer.

Now I have a leftover 256MB PC800-40 ECC sitting around. If I purchased a single stick with identical specifications, will the motherboard disable the ECC feature and run the ECC pair alongside the non-ECC pair without any problems? The problem before indeed seemed to be that one stick in the pair was ECC and the other non-ECC, though they did run. The computer is a Dell Dimension 8200.
a c 78 } Memory
December 7, 2008 1:02:48 AM

What modules are currently installed? 2 x 256MB PC800-40 non-ECC and 2 x 128MB PC800-40 ECC? If that combination works, then replacing the 2 x 128MB PC800-40 ECC with 2 x 256MB PC800-40 ECC should work.
December 7, 2008 5:37:36 AM

GhislainG said:
What modules are currently installed? 2 x 256MB PC800-40 non-ECC and 2 x 128MB PC800-40 ECC? If that combination works, then replacing the 2 x 128MB PC800-40 ECC with 2 x 256MB PC800-40 ECC should work.

My memory is 2 x 256MB PC800-40 non-ECC and 2 x 128MB PC800-40 non-ECC.
a c 78 } Memory
December 7, 2008 12:33:33 PM

Quote:
Stick 3 & 4 128:
Quote :

Samsung Korea 0244 H 256MB/8 ECC
MR18R1624DF0-CM8 800-40 012


The 128MB modules are not the ones that you listed before?
December 10, 2008 4:20:54 AM

GhislainG said:
Quote:
Stick 3 & 4 128:
Quote :

Samsung Korea 0244 H 256MB/8 ECC
MR18R1624DF0-CM8 800-40 012


The 128MB modules are not the ones that you listed before?

Whoops, should read:

1797549,18,339627 said:
Quote:
Stick 3 & 4 128:
Quote :

Samsung Korea 0244 H 128MB/8 non-ECC
MR18R1624DF0-CM8 800-40 012
a c 78 } Memory
December 10, 2008 11:41:07 AM

You should use all ECC or all non-ECC modules. You've already determined that using 2 pairs of non-ECC modules having almost identical characteristics works fine. Mixing both will probably not work properly, unless you can disable parity in the BIOS (and even that might lead to weird results if you have both ECC and non-ECC modules).
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