| 摘要 |
An improved printer is provided that uses a hard disk drive resident in the printer to temporarily store some of the page data of print jobs received by this printer. Since disk access time is relatively slow as compared to access time of random access memory (RAM), only a minimal amount of pages are initially stored on the hard disk drive while the remaining pages of a print job continue to be stored in RAM, such that the pages on the hard disk drive are interleaved with those stored in RAM. Once the pages are stored on the hard disk drive, some of the areas of RAM where they previously resided are released, which allows the printer to free up some of its RAM. In a preferred embodiment of the present invention, only every fourth page is initially stored on the hard disk drive, which effectively spreads out the effects of the slower disk access time across several pages as they are printed. The page data that is stored on the hard disk drive will be divided into tiled "blocks" of print data, so that the individual blocks can be stored in non-contiguous locations within the printer's main memory system of RAM, and later stored on the hard disk drive. If a page of data is to be stored on the hard disk drive, some "empty" space in RAM large enough to hold all of the blocks of data that are being stored on the hard disk drive for this page is reserved in RAM, so that later the blocks that have been stored on the hard disk drive can be retrieved from that drive and will have an immediate place to go in the printer's RAM, which allows the printer to maintain its overall rated printing speed in more situations. These "empty" locations that have been reserved in RAM and known as "shared memory tables," and will contain enough memory locations in the printer's main RAM system to hold all of the compressed bitmap data for all of the blocks for a particular page, or for the "largest" page (in terms of compressed bitmap data) of several pages. If the printer's RAM becomes so scarce that, even after all pages of bitmap data are stored on the disk, the printer still calls for more RAM to be freed, then two or more shared memory tables can be combined with one another in an attempt to make more RAM available to meet the printer's request for more free RAM.
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