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Registered Member #1575
Joined: Sun Jul 06 2008, 12:21AM
Location:
Posts: 6
Hey everyone. So, I'm pretty new to all of this. I was wondering if there was any way to design a circuit that had a port on it to plug a RAM card into, and then maybe some kind of PIC card or something else with software on it to test it? I'm hoping to eventually be able to make a whole bunch of testing rigs for different hardware parts.
I'd love for any information on this, I'm not really expecting someone to just give me a circuit schematic, but if you could point me in the direction of some info that could help me figure out how to do it myself I'd really appreciate it.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
What you need to do is to first define what you consider a successful test. That a PIC can read and write to the RAM does not mean the RAM is usable in a computer. Also it depends in the type of RAM, not all RAM will function well at the slow speeds of a PIC.
If you want to know if the RAM is usable you need to test the RAM at the maximum frequency, lowest voltage (and some times other voltages) and highest temperature it will be used at. If you define a usable RAM module to have less than one error a week you need to test it for several weeks to be confident that it is good. You can test it at worse conditions than it will be used at and say that if it can take 20 minutest of that then it will run for a year under normal conditions without any errors and hope you are right.
One obvious solution is to plug the RAM into the computer it was designed for and test it there at the correct frequency.
Registered Member #1575
Joined: Sun Jul 06 2008, 12:21AM
Location:
Posts: 6
Ok, thank you for the info. So, if a PIC card wouldn't be a good way to test RAM do you have any other suggestions? Is there any way to test RAM as usable in a computer without just having it in a computer and running a software test? If not, I'll just do that, but I was hoping I could actually make a circuit for it, seems like more fun. :)
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
It depends on the type of RAM, if we are talking 20 years old then yes, if we are talking modern RAM then using a PC would be simpler and cheaper. On modern RAM you need to do timing in fractions of a nanosecond and since you are asking about this I expect there is no way you can reach that.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Efficient testing of RAM chips, at least at the factory, requires testing for pattern-sensitive faults. The read or write failure of a bad bit can depend on the state of its physical neighbors, and its row- and column-mates. Design of test patterns, and the hardware to generate them on the fly, requires knowledge of the scrambling between nominal X- and Y-addresses, and the real physical order of rows and columns in each block of the array.
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Testing rig
