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Installing SIMMs

 

Every SIMM has a notch on one end of the stick at the bottom next to the pins. Make sure that this notch is on the same side as the SIMMs currently in your system. Slide the SIMM stick in at about a 45 degree angle making sure it sits completely in the slot. Now, tip the SIMM towards the metal clips on either side of the slot. You should feel them click into place as the stick comes into the upright position. Ensure that the stick is firmly seated in the slot fully (not half in and half out).

You should ground yourself to the machine case (power off to the system). While remaining in contact (skin to metal) to install the SIMMs. I usually rest a forearm on the case side leaving my hands free as well as steadying them.



Here are the standard configurations for banks and SIMM sticks.

	BANK 0		BANK 1
Memory Size	SIMM 1	SIMM 2	SIMM 3	SIMM 4
8MB 16MB 16MB 24MB 32MB 32MB 40MB 48MB 64MB 64MB 72MB 80MB 96MB 128MB 128MB 136MB 144MB 160MB 192MB 256MB 256MB 264MB 272MB 288MB 320MB 384MB 512MB	1MBx32/x36 2MBx32/x36 1MBx32/x36 1MBx32/x36 4MBx32/x36 2MBx32/x36 1MBx32/x36 2MBx32/x36 8MBx32/x36 4MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 16MBx32/x36 8MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 8MBx32/x36 16MBx32/x36 32MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 8MBx32/x36 16MBx32/x36 32MBx32/x36	1MBx32/x36 2MBx32/x36 1MBx32/x36 1MBx32/x36 4MBx32/x36 2MBx32/x36 1MBx32/x36 2MBx32/x36 8MBx32/x36 4MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 16MBx32/x36 8MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 8MBx32/x36 16MBx32/x36 32MBx32/x36 1MBx32/x36 2MBx32/x36 4MBx32/x36 8MBx32/x36 16MBx32/x36 32MBx32/x36	------ ------ 1MBx32/x36 2MBx32/x36 ------ 2MBx32/x36 4MBx32/x36 4MBx32/x36 ------ 4MBx32/x36 8MBx32/x36 8MBx32/x36 8MBx32/x36 ------ 8MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 ------ 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36	------ ------ 1MBx32/x36 2MBx32/x36 ------ 2MBx32/x36 4MBx32/x36 4MBx32/x36 ------ 4MBx32/x36 8MBx32/x36 8MBx32/x36 8MBx32/x36 ------ 8MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 16MBx32/x36 ------ 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36 32MBx32/x36

I have gotten a large number of requests from subscribers who want to know how the math behind RAM works. i.e. How do they get 32MB from 2x4x32.

Let's take for example the RAM configuration 2x16x32.

The first number (two) is the number of physical SIMM modules. if it was 4x16x32 then you would have four physical SIMM modules.

Here's how you work the math:

The last number is the data path in bits. 32 is for non-parity and 36 is for parity, so 2x16x36 means that you have two physical modules that are parity (see edition #12 for more info on what parity is.) To work the math on these, just pretend that the 36 is a 32. So like I was saying, this number is in bits. To convert this to bytes, we divide by eight. 32 / 8 is 4.

Now take your middle number (sixteen in this case) and multiply that by the last answer (four). This gives us 64MB. Now multiply that by the first number (which is the number of physical modules) and you get 128MB of RAM. Pretty easy huh? Here's the math without all the words:

2x16x32

32 / 8 = 4
4 * 16 = 64
64 * 2 = 128MB


Here's another example:

4x32x32

32 / 8 = 4
4 * 32 = 128
128 * 4 = 512MB


As always, there is another way when dealing with math. You can also take the last two numbers and multiply them together (remember, if it's parity (36), then just pretend it's non-parity (32) while calculating.) Now, take that result and divide by 8 (eight bits make a byte), then multiply by the first number (the number of physical modules.) This works equally well, but if math isn't your strong point, this way will most likely involve a calculator or at least scratch paper. Here is the last example we did but using the second formula.

4x32x32

32 * 32 = 1024 bits
1024 / 8 = 128 MB
128 * 4 = 512 MB



There is a lot more I want to cover on this subject, but I think I'm going to quit now. Maybe I'll do some more on this subject in another newsletter. Stuff like waitstates, exactly how the RAS/CAS and signaling works etc...

 

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