The Omega Nebula (also known as the Swan Nebula, the Horseshoe Nebula, the Lobster Nebula, Diffuse Nebula M17, Messier Object 17, Messier 17, M17, or NGC 6618) is an emission nebula in the Sagittarius constellation. It was discovered by Philippe Loys de Chéseaux in 1745. The Omega Nebula is a region of star formation and shines by excited emission, caused by the higher energy radiation of young stars.
External links
Messier 17, SEDS Messier pages (http://www.seds.org/messier/m/m017.html)
The M17 provides five signal pins to indicate which memory space is active: data stack, return stack, code space, A buffer, and B buffer.
The M17 takes two clock cycles for each instruction: one clock cycle to load the instruction from program memory, and another clock cycle to perform the operation while doing a read from or write to one of the stacks in program memory.
The biggest difference between the M17 and the Canonical Stack Machine described in Chapter 3 is that the M17's stack memory and program memory accesses use the same bus, and may reside in the same memory chips.
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