Also called Model 55 486SLC2 System Board Upgrade
193-313 IBM Planar Upgrades For PS/2 Models 50, 50Z, 55 SX And LS
rf5055pu.exe  PS/2 8550/50Z/55 planar upgrade refdisk v1.01

Please tell me of repressed memories about this planar!

Password-override jumper (J11) 

CD-ROM connector (???)

CPU- 486SLC2 25/50 Copro 387SX 
Max Memory on board 16MB  2, 4, or 8MB, 70nS parity 
o   Planar memory support of 70ns, 80ns and 85ns memory SIMMs
Three  SIMM Sockets 

Three 16-bit MCA slots (includes one AVE) 
Video Memory- 1MB DRAM (2 SOJ) 
640x480, 16M: 24 bits/pixel 
800x600, 64K: 16 bits/pixel 
1,024x768, 256: 8 bits/pixel 
Parallel: One enhanced, bi-di with DMA support/
Serialone enhanced with DMA support 
HD Support AT/IDE and existing drive 
Floppy controller supports 1.44 and 2.88MB floppies 
Clock/calendar integrated CMOS battery