http://www.ultratechnology.com/cm522...

Well what the Novix did was it put it under the top of the stack and then it threw away the address on top of the stack. Optionally if you were doing and incremented fetch it put in on top of the stack and incremented the address that was on the top of the stack and everybody was happy. But implementing that in silicon was a mess You have address lines going to the wrong place, the second element on the stack. You have data lines going the wrong way. You have address lines coming to the top of the stack which is equally inconvenient. You need a second cycle to fix up the stack after the operation is completed. To eliminate that it makes sense to move the address out of the way to a special place out of the way and then you clear up the stack to receive the data. Now this really wasn`t my idea. It was Russell Fish`s idea in ShBoom. I had lots of quarrels with Russell but he did have some good ideas and I appreciate them.

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