How to identify RAM chips on an Apple II Plus motherboard

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Joined: Oct 21 2011
Posts: 4

I've recently purchased an Apple II Plus off eBay and it's in working order.

One thing I'd like to know is how much memory it has. It boots into Applesoft BASIC fine, so I'm assuming it has at least 4K of RAM.

Looking at the motherboard, I see all chip sockets in the RAM section are full, but I can't tell what kind of RAM chips they are (4K or 16K?) and I don't know for sure if they are working properly or not.

Is there a way to identify a RAM chip by the lettering on top?

Is there any built-in memory diagnostic in the monitor or in Applesoft BASIC?

Thanks!

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Offline
Joined: Dec 20 2003
Posts: 359
Re: How to identify RAM chips on an Apple II Plus motherboard

Usually the RAM chips have numbers like 4116 on them. If you have all the RAM sockets filled then it's almost guaranteed that you have 48k on a II+. Only the very earliest II+ had memory select blocks. If you should have them then they'll be on the left side of your RAM and marked 4 or 16. If you don't see them then you're using 16k RAM.

To test the RAM you need a utility

Dog Cow's picture
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Joined: Dec 11 2008
Posts: 463
Re: How to identify RAM chips on an Apple II Plus motherboard

Chips will typically have two numbers on them: a date code, and an ID. The date will be four digits. The left two digits are the year, and the right two digits are the week number. For example, a date code of 8105 Indicates a manufacture date in February of 1981.

The second number is the ID of the chip. RAM chips for the Apple II and II Plus are either 4116 or 4114. The 4116 is a 16 byte x 1 bit DRAM, and the 4114 is a 4 byte x 1 bit DRAM. Since the Apple II is an 8-bit machine, it takes 8 of these chips to store an entire byte.

If your Apple II Plus has memory selector blocks, it could have fewer than 48k of RAM. However, it is EXTREMELY UNCOMMON to find any Apple II Plus with fewer than 48k of RAM. If your Apple II Plus does not have memory selector blocks, then it is 99% guaranteed to have 48 k RAM, since that is what those models shipped with.

Apple II Plus with memory blocks:
http://i158.photobucket.com/albums/t118/bradandjennifer_2007/80251-1.jpg
They are on the left, near the power supply, and say 16K upsidedown.

Apple II Plus without memory select blocks:
http://www.classiccmp.org/dunfield/apple2/h/pboard.jpg

Quote:

Is there any built-in memory diagnostic in the monitor or in Applesoft BASIC?

There isn't any test program built-in, but you can write one in Applesoft:

10 PRINT “WRITING MEMORY”
20 FOR I = 6000 TO 49151
30 I%= I
40 J%=I/256
50 POKE I%,J%
60 NEXT I
70 PRINT “CHECKING MEMORY”
80 FOR I = 6000 to 49151
90 I%=I
100 J%=I/256
110 IF PEEK (I%) = J% THEN GOTO 140
120 PRINT “ERROR AT ADD:”;I%;” DATA:”;PEEK(I%);” EXPECTED:”;J%
130 GOTO 160
140 NEXT I
150 PRINT “NO ERROR”
160 END

This program was taken from: Mr. Willegal's site: http://www.willegal.net/appleii/appleii-repair.htm

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amauget's picture
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Joined: Jan 3 2011
Posts: 242
Re: How to identify RAM chips on an Apple II Plus motherboard

Hello,

See my previous post for a simple memory test.

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Apple II forever