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View Full Version : Piggy-back RAM chips for 5170



Druid6900
May 6th, 2017, 06:46 AM
I have a whole set of these piggy-back RAM chips, along with a NPU and, possibly, a CPU that came out of a 5170 that was trashed by an exploding battery.

The board was in good enough shape to be able to run a system board and memory test, but was falling apart as we worked on it.

The memory and processors tested out good for about 5 trips through the test and then it gave up the ghost.

They have been sitting in a sealed anti-static bag for several years now.

Are they worth anything?

gslick
May 6th, 2017, 11:13 AM
The 128Kbit piggy-back DRAM chips do have some value. I have an AT 5170 Type 1 motherboard which uses those. Two or three of them are currently bad. I picked up another whole working motherboard before I got around to finding replacements for the bad piggy-back DRAM chips. I would still like to get them replaced as the motherboard is fully functional otherwise.

Stone
May 6th, 2017, 11:35 AM
As the name suggests, two 64K chips, one on top of the other, is all you need.

evildragon
May 6th, 2017, 11:41 AM
Well, they aren't just generic 64K's piggy backed. If they were, you wouldn't be able to address just one of the chips.. If you were to separate them, they wouldn't work as standard 64K's. In fact, I don't believe the bottom chip even has writing on it, if I remember. They are both internally wired differently, so the stacked chips act like a single 128K.

modem7
May 6th, 2017, 03:29 PM
As the name suggests, two 64K chips, one on top of the other, is all you need.

They are both internally wired differently, ...
The differences shown at [here (http://minuszerodegrees.net/temp/3/temp_732567618712.png)] would need to be catered for.

Compared to a 4164:
* The 41128 package has two RAS pins
* So that those two RAS pins are next to each other, the two 64K chips have their Din and WE pins shifted by one pin position.

Also, some 4164 use pin 1 to specify the refresh mode.


The 128Kbit piggy-back DRAM chips do have some value. I have an AT 5170 Type 1 motherboard which uses those. Two or three of them are currently bad. I picked up another whole working motherboard before I got around to finding replacements for the bad piggy-back DRAM chips. I would still like to get them replaced as the motherboard is fully functional otherwise.
In case you have not seen it, a list of possible chips is at [here (http://minuszerodegrees.net/memory/41128.htm)].

Druid6900
May 7th, 2017, 06:06 AM
What would a general consensus be of a fair market value then?

I know what people are asking for them, but, you don't always get what you ask.