Figuring out substitute parts?

[Mrwoodchuck]

Hi all,

So a little back ground info on my self.
I have been working with computers most of my life, I have dabbled in electronics here and there but never really got into it "radio shack 300 in 1 kit"  .
This last year I have spent some time getting to know the basics, I think I am ready for my first big project.

I decided on an open source super nintendo cartage that you can load your backups onto, it seemed well written but little support.

The problem I came across was in the parts list, there is a memory chip that i found at one company that seems to have the last 25 chips on earth.
MT45W8MW16 micron
http://www.questcomp.com/questdetails.aspx?pn=MT45W8MW16BGX-708WT&pnid=346509&stock=Yes

So because of this I was wondering how do we know what are compatible substitutes for old parts that no longer are made.

here is a link for the project encase anyone was curious.
http://sd2snes.de/blog/downloads

any info would be helpful as I said i'm still kind of a rookie so don't be too harsh if this is a dumb question.
Thanks all.

[Skimask]

Here's what I did...

Go to www.digikey.com or mouser, or whatever your favorite dealer is...

Search for RAM

Search for all packages with 54 pins

Search for all packages with 54 pins that are BGA types

Search for all packages with 54 pins that are BGA types that are 8Mx16

Search for all packages with 54 pins that are BGA types that are 8Mx16 that are pseudo-static RAM (PSRAM)

Ok, Digikey doesn't stock the exact Micron types, but there are others if you can match them up...not at Digikey, but they are out there.


P.S.  Before starting a project, you might want to check if parts are available in the first place.

[Mrwoodchuck]

Thank you for the quick reply! 

I was not sure if ram would be an interchangeable part, like how capacitors or resistors are.

I assumed that ram pin outs would not be the same for different manufactures, but I guess I should have grabbed the spec sheet and compared to a different version.

Again total rookie, after reading your post it totally makes sense.
I was more thinking if i ordered everything and the chip was not comparable it might fry something.

very good tip, I did not quite start the project yet I just downloaded all the materials and adjusted the parts list as his were all listed for uk company's and I live in the us.

That was just one of the parts I was lost on.

Again thank you for the smack in the head I needed. Lol

[Skimask]

Well, the steps I gave you just kinda help you drill down to what will actually FIT.
It's up to you to grab the datasheets, look at the chip pinouts, look at the ratings, etc., and decide if the 2 parts are interchangeable or not.
Worst case, you find another one that might fit, and ask the question again.
(ok, maybe not the worst case, but you get my drift...)

[Mrwoodchuck]

Now that I have done some more searching,

I am still not able to locate a module to replace this one, I have been on newark.com, digikey, mouser, a few uk sites.
The closest I have come is the site I listed above  and that seems a little iffy.

So I guess what im asking at this point is how would you redesign things to make it work with newer types of chips with these ideas in mind, because they will not keep producing chips.

I assume the firmware would have to be rewritten and basically start from scratch as the pcb layout would change so on and so on.

thanks all.