Solved PC won't boot, too much RAM.

October 17, 2015 at 13:14:28
Specs: Windows Vista, Pentium 4/ PC133
I am upgrading RAM on a D845HV Intel motherboard with a Pentium 4 2.6GHZ 400MHZ FSB 512KB cache and 845 chipset with the latest BIOS P15. Also, it is running windows vista and has a 256MB DDR2 ATI Radeon X1300Pro installed in a 4x AGP slot. The documentation for this motherboard shows that it can theoretically take 2GB (two DIMM slot version) or 3GB (three DIMM slot version). The board I have has three DIMM slots. So, I tried to upgrade to 3GB, but that didn't work. I tried 2.5GB and that did not work either. 2GB in two DIMM slots with the third left empty works. When it fails, the machine does not boot and I can not enter CMOS. Working or not, POST displays the total amount of RAM installed correctly. And before I started upgrading I did have RAM installed and working in the third slot albeit a lower amount, so the slot itself should be fine. The memory I am using are PC133 128Mx64 un-buffered Non-ECC 168pin SDRAM. What would be preventing this system from reaching the theoretical maximum of 3GB?

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✔ Best Answer
October 18, 2015 at 06:20:57
Look at what I put in bold in my other response. For 3GB RAM to work, all three 1GB sticks must be based on 512 Mbit technology.

October 17, 2015 at 19:42:15
"The D845HV/D845WN boards have been designed to support DIMMs based on 512 Mbit technology for a maximum onboard capacity of up to 3 GB, but this technology has not been validated on this board."

Why are you wasting your efforts on such an outdated setup?

message edited by riider

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October 17, 2015 at 22:43:46
1. It's available.
2. It doesn't cost anything.
3. I have new and new works just fine without any effort from me.
4. Because old does not.
5. And because it does not, I might just learn something new.

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October 17, 2015 at 23:51:52
Are the three DIMMs identical? Same manufacturer? Have you tried every combination of them to ensure that they all work, and all work together?

I appreciate the experimentation if you already have all the hardware, but it wouldn't make sense to try the upgrade if you didn't already possess the appropriate DIMMs - nowadays they probably cost more than a m/b + RAM that could run rings round that old equipment.

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October 18, 2015 at 03:03:17
Well all the 1GB sticks are identical and marked "PC133 128Mx64 UNB Non-ECC SDRAM". One turned out to be bad however. But I don't think that is the end of the story. I had also installed 2.5GB of known good working RAM and it still would not boot.

The defective RAM was identified as follows. POST would count up to the 3G, but the machine would reboot and show progressively less memory after a couple times down to just 2GB. The machine never did boot with all three 1G sticks installed. And to clarify things before my confusion becomes yours, the defective stick was only ever installed in slot 0.

Assuming that the problem would be in slot 3 due to the MB documentation (see riiders post #1) I pulled the RAM from its slot. POST would count up to 2GB, but the machine would still not boot. At that point, I noticed mechanical damage on the surface of two of its IC's. That made it only suspect to me, so I reinstalled it. After reinstalling it, the machine stopped showing anything on the monitor. It was then that I realized it was not the slot 3 RAM I had just pulled out and stuck back in but the slot 0 RAM. I had been looking at it backwards and only realized it when the monitor stopped showing anything. POST didn't seem to care as much as I thought it would because it had reported on the RAM even with no stick in slot 0. Does that seem odd to anyone else?

Anyway, the machine has now got two identical 1GB of RAM installed (one in slot 0 and one in slot 1). There is nothing in slot 3. And it boots with just this 2GB installed.

As I said earlier, I had installed 2.5GB and the machine failed to boot. I had put the original 512MB stick from before the upgrade into the empty slot 3. So, at this point and as far as I can confirm, the RAM sticks were no longer identical at least in terms of size. That stick is marked "512MB,SDR DIMM, H 64WHS STK 4603841". I looked that up online and found a website. I am not sure if it is an exact match. Mine does not say dell on it and like the RAM in the link below does not say whether or not it is buffered or unbuffered. Here is the link.


If you trust that the link matches, everything would seem compatible except that it does not say whether it is buffered or unbuffered.

I don't think the size difference is an issue, but I can't be sure of that.
And I don't know if you can mix UNB (unbuffered) and buffered memory and still boot?

Sorry if this post bounces around too much like flashbacks or flash forwards in a movie.

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October 18, 2015 at 06:20:57
✔ Best Answer
Look at what I put in bold in my other response. For 3GB RAM to work, all three 1GB sticks must be based on 512 Mbit technology.

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October 18, 2015 at 13:50:56
The IC's on the 1GB RAM sticks are marked HYB39S512800AT-7.5.

These are 512Mbit chips. They way I read it, each register on the chip is 16Mbit wide, there are 8 registers per bank, and 4 banks per chip. I'm not sure how that adds up to a 128Mx64 or 1G module (which has 8 chips per side). Anyway, long story short it says 512 in the part number of the chip making it 512Mbit technology.

The 512MByte module I used on the other hand has HYB39S256800DT-7.5 chips on it.
There are 16 chips total on the module. I'm not sure how that works out to in ?Mx? notation and maybe the 64WHS is some alternative marking to that. But again, long story short, the part is marked 256, so it is 256Mbit technology.

So, what that statement is leaving out then, is that for memory to be installed between 2GB and 3GB total. A third stick whether 1GB or less must have 512Mbit chips on it.

And that for total memory less than 2GB it doesn't care if its 512 or 256 Mbit tech.

If that is the case, perhaps my whole problem has been the defective 1GB stick all along.

I am still confused about how all the memory geometry all works out. I'll have to take more time to look into that.

Also, I noticed the 512Mbyte stick has an H marked on it "512MB, SDR DIMM, H". Any idea what H means?

message edited by ISAmad

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October 18, 2015 at 14:28:52
I had an error in my last post. It should have said 8 registers not 4, I corrected it.

So then that means 8 registers per bank x 16Mbits per register = 128Mbits per bank.

That is the 128M in 128Mx64.

And 4 banks per chip times 16 chips = 64

or 128Mbits in 64 banks across 16 chips.

128Mbits x 64 banks = 8192bits. 8192bits / 8 bits per byte = 1024bytes. 1GB.

I am still trying to see how the PC actually addresses the module and understand rank and figure the actual bus width.

Anyway, I got an RMA, should have another 1GB stick soon, and we'll see what this MB can take.

message edited by ISAmad

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February 13, 2016 at 15:37:01
I was expecting an exchange out of that RMA, but it turned into a one sided return of the defective stick. The seller never got back to me about honoring the original bid and I became less interested in pushing it over time.

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