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| Click here to select a new forum. | | Will this ram work?? | Posted by: maceffects on 2012-05-06 21:22:56
I have a (only one but can get two) of the following memory stick:
Memory (RAM): 128MB=1X128MB FAST PAGE
FAST PAGE
Number of Memory Chips: 24CHCIPS
Memory Capacity: 128MB=1X128MB FAST PAGE
Number of Pins: 72PINS
Density: 16X4 FAST PAGE
Will this work in the LC475, if not will two of these work in a PowerMac 6100?
| Posted by: trag on 2012-05-08 11:07:19
It will probably work in the LC475. It may or may not work as one of a pair in the 6100.
There are probably eight smaller narrower chips and 16 larger wider chips, with two or four more pins per chip on the larger ones.
The larger chips are 16M X 4, which means that they have 16 million (2^24) addresses and they read or write four bits at a time.
Eight of these chips bundled together creates a 16M X (8 X 4) => 16M X 32 bank of memory, which is 16M X 4 bytes => 64 MB of capacity.
The SIMM is 32 bits wide (see 16M X 32 above) as are all 72 pin SIMMs and there are sixteen of these large chips on board. So there are two 64 MB banks on the SIMM for a total capacity of 128 MB.
The remaining eight smaller (16M X 1) chips provide parity and so are irrelevant to Macintosh operations.
The two banks on the SIMM are addressed separately by selectively activating the four RAS_ pins on the SIMM in pairs. In my experience, sometimes the RAS_ pins/wires are connected together on the SIMM in pairs which do not correspond to the way that they are paired on the PM6100 logic board. In those cases the SIMMs won't work with the PM6100.
There may be resistors on the SIMM which will allow you to change the pairing of the RAS lines on the SIMM, but I'm not certain.
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