Editing IBM PCjr (section)

====Limited hardware expansion====
Computer dealers quickly identified the PCjr's limited hardware expansion capability as another major disadvantage.<ref name="zientara19840409">{{cite news | url=https://books.google.com/books?id=jC4EAAAAMBAJ&pg=PA13 | title=PCjr sales below expectations, dealers say | access-date=April 3, 2011 | work=InfoWorld | author=Zientara, Marguerite | date=April 9, 1984 | publisher=IDG}}</ref>{{r|time19840402}} ROM cartridges had small storage capacity,{{r|cook19840306}} requiring, for instance, two cartridges and a floppy disk for the PCjr version of Lotus 1-2-3, which also had difficulty fitting complex spreadsheets into 128K of RAM.{{r|trivette198504}} IBM published technical details for the PCjr as it had done for the IBM PC to encourage third parties to develop accessories, but did not offer a second floppy drive, hard drive,{{r|wp19831106}}<ref name="ruby198402" /> or memory beyond 128&nbsp;KB.{{r|hoffmann198403}}{{r|halfhill198410}}

While multiple sidecar expansion units could be attached, they took up a lot of space, and the computer required additional power supplies to support a second floppy drive or more than one sidecar. IBM advised against adding more than four sidecars.<ref name="ruby198402" /><ref name="mccarroll19841224" />{{r|levy198501}} The PCjr also lacks a [[Direct memory access|DMA]] controller, so the 8088 CPU has to service floppy disk transfers directly, causing the system to momentarily freeze while accessing a disk. The PCjr also cannot use modems faster than 2400 baud.<ref name="hoffmann198403">{{cite web | url=http://www.atarimagazines.com/creative/v10n3/74_IBM_PCjr.php | title=IBM PCjr | access-date=February 25, 2011 | author=Hoffmann, Thomas V. | date=March 1984 | work=Creative Computing | pages=74}}</ref>{{r|levy198501}}{{r|manes19850528}}