Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucsdhub!hp-sdd!ncr-sd!ncrcae!sauron!stevem
From: stevem@sauron.Columbia.NCR.COM (Steve McClure)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: One more Amiga RAM question. ;*)
Message-ID: <2021@sauron.Columbia.NCR.COM>
Date: 28 Feb 90 13:07:00 GMT
References: <928@orange9.qtp.ufl.edu>
Reply-To: stevem@sauron.UUCP (Steve McClure)
Distribution: na
Organization: E&M-Columbia, NCR Corp, W Columbia, SC
Lines: 51

In article <928@orange9.qtp.ufl.edu> sutherla@qtp.ufl.edu (scott sutherland) writes:
>
>
>	Well, I have asked several questions about memory expansion and
>the Amiga, specifically w.r.t. the A2091 and A2630.  Now I am more 
>informed AND more confused.  What I have been told is that, for the
>A2091, I need 16 256K x 4 CMOS DRAM 120 ns chips for 2 Megs.  I can find
>these in Computer Shopper for ~8 ea.  Now, for the A2630, I have been
>told that I need, get this, 256K x 4 CMOS DRAM 100 ns chips (or faster).
>NOW I AM REALLY CONFUSED.  
>
The key here is that memory is memory.  8-bit, 16-bit, 32-bit all refer to
the number of bits that can be accessed in one read, in other words in
parallel.  The chips you need are 256Kx4, x4 means 4 bits in parallel.
Therefore you need 4 chips to have memory that is accessable 16 bits at a time.
This means you should be able to populate the board in 256K/2*4 increments.
						        ^^^^^^ it takes 
					two chips to make 8 bits or a byte.

There is some organization to the chips.  The most popular being 256Kx4 and
1Mx1 in 1 megabit chips.  The design of the board determines how many bits
can be accessed in parallel.

>	A couple of extra questions.  I have been told that I MUST use CMOS
>chips and not NMOS chips.  None of the places in the Computer Shopper
>specify whether the chips they list are CMOS or NMOS.  How do I differentiate?
>And finally, Dave Haynie told me that the chips for the A2630 were NOT only 
>256K x 4 CMOS DRAM 100 ns chips, BUT that they must be in the ZIP package.
>
>What in the world is a ZIP package???  Again, none of the advertisers in CS 
>mention anything about ZIP!!  They mentions SIMMS, but NO ZIPS.  Why do I need
>ZIP?  How do I determine if a chip advertised in CS is ZIP or not???
>

Chips come in different packages, or physical designs:
	Dual Inline Package - DIP's 	pins are in two parallel rows.
					.......
					.......
	Zig-Zag Inline Package - ZIP's	pins are in one row, slightly offset.
					. . . .
					 . . . .
	A host of others.

You usually have to ask about package styles and chip types.  Typically, the
parts you see advertized in CS are CMOS DIP's for this chip type.

Steve
-----
Steve.McClure@Columbia.NCR.COM
The above are my opinions, which NCR doesn't really care about anyway!
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