Finding Datasheets for Old Parts

[janagyjr]

I've found some specs on the following chips, but no actual data sheets at the usual places (findchips, datasheetcatalog.com, alldatasheets, etc.; I copy/pasted from a document I made to put the info I did gather into):

MCM6256BP10
General Purpose Dynamic RAM - Early write capability
Motorola

Number of Words=256k
Bits Per Word=1
t(acc) Max. (S)=100n
tW Min (S)=200n
Output Config=3-State
P(D) Max.(W) Power Dissipation=600m
Nom. Supp (V)=5.0
Package=DIP
Pins=16
Military=N
Technology=NMOS

UM2128-1
General-Purpose Static RAM - ICC 100mA max
United Microelectronics

Number of Words=2k
Bits Per Word=8
t(acc) Max. (S)=150n
tW Min (S)=150n
Output Config=3-State
P(D) Max.(W) Power Dissipation=1.0
Nom. Supp (V)=5.0
Status=Discontinued
Package=DIP
Pins=24
Military=N
Technology=NMOS

P21256-12
General Purpose Dynamic RAM - Page Mode Cycle Time 120ns min
Intel

Number of Words=256k
Bits Per Word=1
t(acc) Max. (S)=120n
tW Min (S)=230n
Output Config=3-State
P(D) Max.(W) Power Dissipation=1.0
Nom. Supp (V)=5.0
Package=DIP
Pins=16
Military=N
Technology=NMOS

I'm surprised that the above specifications are available even without an available data sheet. Any help with these chips would be appreciated (I salvaged them out of an old Dell and would like to recycle them if possible).

 

[(*steve*)]

You'll find one interesting issue with dynamic RAM is that unless you refresh it frequently, it loses its memory.

In the earliest IBM PC's there was an interrupt routine that refreshed all the memory (and I'm stretching brain cells here) 18 times a second. It used (again, from memory) around 7.5% of the available CPU power.

I recall a program that would slow down these refreshes (because memory was almost always way better than the minimum spec) and frequently you could get away with two or three per second.

OK, so with that little bit of history, you'll see that using these chips in a design means that you'll either need to only want to store the data for a very short period, or provide some mechanism for refreshing.

You will probably find that the techniques applicable to almost any dynamic RAM are applicable to almost all of them. The things that tend to change are the delays between states. You may have seen this in the BIOS of a PC. CS, RAS to CAS and other alphabet soup.

This might be helpful. (And this too)

As you can see, using DRAM is not trivial. Static RAM, in comparison, is *way* easier to use.

You'll probably find more information if you search on just the numbers. Also try chipdocs.com. They have a search that seems better than the free datasheet sites, however you have to pay to get access to their data. BUT they do give you a list of the device names, so you can use that to further your search. For example, looking up 6256 turns up a whole swag of full part numbers that look suspiciously correct maybe it's a 416256? doc.chipfind.ru is another site that has datasheets, an plugging in 416256 into this gives you an enormous number of options.

 

[janagyjr]

Whoa. That's quite intensive indeed. Hrm. Still, they could be useful (at least to someone). I'll hold on to them for a bit and see what I can do with them.

Thanks for the search tips Steve.