Hints and tips on the PS/2 P70 portable

This is just a collection of snippets on the PS/2 P70 (8573) portable, gained while playing with the one that I own (it cost me 30 cents).


The P70 has four 72 pin SIMM slots. Unlike the P75, the largest SIMM that can be used is 2MB. The speed can be 85ns or 80ns.

Getting the case undone

To the uninitiated, it is not entirely obvious how to remove the back of the case. There are three large screws. One is inside the hinged cover, at the corner of the case. The other two are 'inside' the 'feet' of the case, on the bottom. After loosening all three (they are captive screws) gently lever the back away from the rest of the case.

Fitting a SCSI hard drive

The P70 comes with one of the IBM Direct Bus Attachment (DBA) hard drives; these are the black ones that have a single wide edge connector whicb is essentially the MCA bus; the controller is integrated on the actual drive. These are not compatible with anything else, so the opportunity for upgrading them is very limited.

One solution is to fit a SCSI disk, at the expense of one of the two slots in the machine. This is what needs to be done:

  • Open the case, and remove the disk cage (three screws, one on the bottom and three inside). Also remove the disk cable from the planar.
  • Fit a SCSI controller card. I used a standard IBM SCSI controller, with the onboard terminator. It would be better to use one of the later ones with automatic termination, if you have one, to save using an external terminator or opening the case every time you want to plug in (say) a CDROM drive.
  • Remove the old disk from the disk cage, and fit the new one. The disk I used was a slim 350MB one; I had to drill some extra mounting holes to secure it, and for safety I fitted a thin sheet of insulating material next to the electronics board (I used part of an old CDROM sleeve).
  • Get, or make, a SCSI cable. This is a 50 way cable with a 50 pin header on one end, and a 50 pin edge connector on the other. I made a custom cable so that it could be exactly the right length with no extra folds; there isn't much room inside the P70 case.
  • Install a power cable. This is the most fiddly bit. Obtain a standard 4 pin drive power cable, with a few inches of wire on it. Choose one where the wire isn't too thick, again to save space. Graft this into the output cables from the power supply; I did this using automobile crimp connectors for joining two wires together (just use a pair of pliers to close them).
  • Fit the power cable to the drive, also the SCSI cable. Install the drive. Finish by connecting the other end of the SCSI cable to the controller.
  • Boot from the reference disk and run autoconfiguration. Run diagnostic tests, and with luck that will be it!
  • Diskette drives

    The diskette drives on these machines suffer badly from the ingress of dirt and dust, mainly due to the orientation of the drive. The head mechanism also has to push the heads up against gravity, which causes excessive actuator spindle wear. Both of these can cause slow response to the Power On System Test (POST), generating errors such as 601 (diskette drive failure) or 162 (configuration error due to the failure of the drive to be detected).

    The correct FRU number for a replacement diskette drive is FRU 38F5936. However, it seems that FRU 64F0162 will also fit, and is electrically compatible. This drive is commonly used in the following machines: Model 55SX (8555), Model 60 (8560), Model 65SX (8565) and Model 80 (8580). It is also used in some Model 85 (9585), Model 90 (8590) and Model 95 (8595) systems, except of course when a 2.88MB drive is fitted! Note that the 8560, 8565 and 8580 have also used a different drive with a 40 pin card edge connector rather than the 34 pin header; this will not fit. In all cases, it will be necessary to remove the plastic drive sled from the base before fitting the drive to a P70. The blue plastic button may be a different length, so it may be a good idea to keep the button from the old drive (it simply pulls off) to fit to the replacement drive.

    The reference diskette

    The reference diskette is essential for configuring the system. The file you need is called RFP70A.EXE, on the IBM PCC BBS web site. After downloading the file, you will need a blank formatted 1.44MB diskette; run RFP70A.EXE and it will make the diskette. If you look at this diskette under Windows (even just a DIR command) you may destroy the special signature; you can use the REFSTAMP utility to restore it.

    The online Hardware Maintenance Manual

    The P70 (and P75) have quite a useful Hardware Maintenance Manual (HMM). This can be found online, at ftp://ftp.pc.ibm.com/pub/pccbbs/mobiles/tpvol1.pdf. Don't be put off by the fact that this looks like a manual on ThinkPads; chapter 6 does actually cover the older machines.

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    Last Updated: 24th August 2001
    © 2001 by Bob Eager, Tavi Systems