LaserJet is the brand name used by the American computer company Hewlett-Packard (HP) for their line of dry electrophotographic (DEP) laser printers.
HP LaserJets employ electro-photographic laser marking engines sourced from the Japanese company Canon. Most early printers used internal firmware, controllers, associated software, and drivers developed internally by HP and were considered their "value add" to the standard printer engines.
The first HP LaserJet and the first Apple Inc. LaserWriter used the same Canon print engine. The internal engine evolution differences were mostly superficial, with the main difference being in the onboard RIP controller, and the user-interface evolution (discussed below). This sharing of an identical Canon engine in two competing products continued with the HP LaserJet II/III and the Apple LaserWriter II, which also used the same internal Canon print engines.
Beginning with the LaserJet 4000, HP nearly completely outsourced its print-engine evolution work to Oak Technology, now Zoran Corporation, among many other suppliers, creating a much greater divergence in print-engine evolution between Apple and HP.
The first HP LaserJet and the first Apple Inc. LaserWriter used the same Canon print engine. The internal engine evolution differences were mostly superficial, with the main difference being in the onboard RIP controller, and the user-interface evolution (discussed below). This sharing of an identical Canon engine in two competing products continued with the HP LaserJet II/III and the Apple LaserWriter II, which also used the same internal Canon print engines.
Beginning with the LaserJet 4000, HP nearly completely outsourced its print-engine evolution work to Oak Technology, now Zoran Corporation, among many other suppliers, creating a much greater divergence in print-engine evolution between Apple and HP.
Upgrading memory of older models
Many older LaserJets and other HP printers, including LaserJet 4+, 4MV, 4MP, 4P, 5, 5M, 5MP, 5N, 5P, 5se, 5Si MOPIER, 5Si, 5Si NX, 6MP, 6P, 6Pse, 6Pxi, C3100A; DesignJet 330, 350C, 700, 750C, 750C Plus; DeskJet: 1600C, 1600CM, 1600CN; and PaintJet XL300 used proprietary 72-pin HP SIMMs for memory expansion. These are essentially industry-standard 72-bit SIMMs with non-standard Presence Detect (PD) connections. It is very often possible to adapt a standard 72-pin SIMM of appropriate capacity to support HP PD by soldering wires to pads, a simple task. HP printers of this type specify that RAM not faster than 70ns be used; this is probably due to a limitation of the PD encoding, and faster RAM can actually be used so long as the PD encoding indicates a speed of 70ns or slower. All printers will work with FPM (Fast Page Mode) memory; many, but not all, will work with EDO memory.
Many older LaserJets and other HP printers, including LaserJet 4+, 4MV, 4MP, 4P, 5, 5M, 5MP, 5N, 5P, 5se, 5Si MOPIER, 5Si, 5Si NX, 6MP, 6P, 6Pse, 6Pxi, C3100A; DesignJet 330, 350C, 700, 750C, 750C Plus; DeskJet: 1600C, 1600CM, 1600CN; and PaintJet XL300 used proprietary 72-pin HP SIMMs for memory expansion. These are essentially industry-standard 72-bit SIMMs with non-standard Presence Detect (PD) connections. It is very often possible to adapt a standard 72-pin SIMM of appropriate capacity to support HP PD by soldering wires to pads, a simple task. HP printers of this type specify that RAM not faster than 70ns be used; this is probably due to a limitation of the PD encoding, and faster RAM can actually be used so long as the PD encoding indicates a speed of 70ns or slower. All printers will work with FPM (Fast Page Mode) memory; many, but not all, will work with EDO memory.
(Cridited to Wikipedia)
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