HP LaserJet - Upgrading Memory of Older Models

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. One can often 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 decoding, 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.

Even older models, such as the LaserJet II, IID, III, IIID, and 4/4M (i.e. not 4 Plus), used proprietary memory expansion boards. For example, the II and IID models used a roughly 4" square memory expansion board populated with DIP DRAM chips and a two-row header connector (with pins on standard 0.1" centers).