
The What and Why of ZEnterprise Millicode - rbanffy
http://archive.ibmsystemsmag.com/mainframe/administrator/performance/millicode_rogers/
======
peter_d_sherman
Excerpt:

"Microcode can be used to enable an inexpensive low-end machine to look at
software just like an expensive high-end computer. An example of this from the
S/360 era was the Model 30. Physically, the Model 30 was an _8-bit machine
with 8-bit registers and 8-bit data paths_. The architected general-purpose
registers were not hardware registers at all, but actually resided in core
memory. Yet, _by using microcode in a read-only store (ROS), the Model 30
presented the full basic S /360 architecture—in which the registers and
operations are defined—as if it were a 32-bit machine_."

8-bit to 32-bit, just like magic...

Probably a lot slower though, but magical nonetheless...

Great article!

