IBM QMS 4525 manual 406&RPSLOH$KHDG7HFKQRORJ\$SSURDFK, Documents

Crown

Multitasking

Rather than rasterizing the page as a whole, the Crown operating system compiles the page into an intermediate, compressed QMS display list. If the printer is busy printing, the intermediate blocks of data are stored in printer RAM until the printer is available for printing. This process allows more efficient storage as well as concurrent com- piling, rasterizing, and printing. This, in turn, provides faster printing speeds.

406￿&RPSLOH￿$KHDG￿7HFKQRORJ\￿$SSURDFK

	Intermediate
Compiler	Blocks	Rasterizer		Print
	complied
PDL Interprets			Bitmapped	Engine
	into the		Pages
PDL and		Rasterizers
	Printer's
Creates		Intermediate		Prints
	Native
Intermediate	Language	Blocks as		Collated
			as needed
Blocks		needed		Documents
	(32KB each)

Collated Documents

By separating the printing process into the two operations of compil- ing into an intermediate format and rasterizing, the printer does not have to re-create an entire page from scratch each time it is printed. The more time-consuming compilation operation is done only once per page. Each page may be printed multiple times simply by rasteriz- ing the intermediate format.

An important feature of compile-ahead technology is simultaneous compiling, rasterizing, and printing. This capability changes what has traditionally been a sequential process into a parallel operation where several processes (compiling, rasterizing, and printing) work indepen- dently. In other words, the compiler changes the page description into intermediate blocks and stores them in memory; the rasterizer pro- cesses the intermediate blocks as needed by the print engine; and the print engine prints the pages. And all these tasks are done at vir- tually the same time.

Because the intermediate blocks are compiled ahead, stored effi- ciently, and processed quickly, after the first copy of a page is printed, all other copies of that page are printed at the printer's rated speed and in any order, including being automatically collated. In addition, parallel operation allows the printer to work on different phases of several print jobs at one time, employing the print engine more effi- ciently because it does not have to be turned off between print jobs.

2-26 QMS 4525 Print System User's Guide

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