Mailinglist Archive: opensuse (911 mails)

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Re: [opensuse] memtest only seeing 48GB out of 64GB?
On 12/31/2015 12:12 AM, Lew Wolfgang wrote:
I have added memory to both my desktop and ThinkPad computers. I didn't
even use the same make of memory and all works fine. For example, my
ThinkPad came with 4 GB of Samsung memory and added 4 GB of Kingston.
It just worked without problem.


I have a hunch it's more related to signal timing and clock speed rather
than capacity. Lower speed DRAM probably has fewer issues than high
speed ones. I had a problem like Greg's on a SuperMicro server mobo
some years ago. I never did get it working and just lived with
48-GB. I've
got one now with 128-GB and it's rock-solid. Go figure...

That boils down to board quality. The desktop system got a new
motherboard a couple of years back and has an Intel I7 CPU. I bought
some memory initially and more some time later.

Incidentally, many years ago, I used to work with core memory, which was
made with tiny ferrite rings arranged in an array strung over extremely
fine wires. Now that was fussy about timing in that if you replaced one
inhibit line transistor or one of the driver/sense ICs connected
directly to the array, you had to replace all of them with devices from
the same batch. Those memory boards were either 8 or 16 KB on a 15"
square board. On my shelf behind me, I have a core plane from a Collins
B8500 computer. it contains 4096 cores and is about 5" square.

Here's a picture of it:
https://drive.google.com/file/d/0B5LapMwk8iPrNkFZUXA4cmd5dTg/view?usp=sharing
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