Intergrated circuit speed question

Just wondering if an ic that is 100 nanoseconds can be replaced by one that is 120 nanoseconds or will that not work?

100ns and 120ns are access times, which is the inverse of speed. Lower access time means higher speed (faster operation).

Typically, you want replacements to be the same speed or faster; which means the same access time or LOWER.

That said, many things were designed and/or built with significant margin, and will work with slower devices. So, I'd say: there's a good chance a 120ns device will work fine... but you'll be taking your chances as there's no guarantee.
 
It all depends on clock speed of the CPU, how fast it access the RAM, and if it uses any "wait states"...

A good rule of thumb is 120ns to 8MHz and 100ns to 10MHz when dealing with older dynamic RAMs and zero wait states.
 
Just wondering if an ic that is 100 nanoseconds can be replaced by one that is 120 nanoseconds or will that not work?

Quick answer depends on the board and the ram chip.

Safest answer just replace it with the same speed.

Longer jibberish answer

If your board was designed to use 120 nanosecond ram chips. Putting a 120 where a bad 100 is isn't going to effect you much.

If your board was designed to use 100 nanosecond chips. You will be over driving your 120. Not a real problem if your using nec brand chips but you do add an element that might add a possible unstabliness in your game.
 
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