8573 P70

rfp70a.exe P70 386 Reference Disk v1.04 (zipped image)

190-053 PS/2 MODEL P70 386 (8573-031)
189-074 PS/2 MODEL P70 386 (8573-061 / 121)
SHS15F2198 IBM PS/2 Model P70 386 HMS
SHS64F3994 IBM PS/2 P70 386 HMR
tpvol1.pdf HMM for IBM PS/2 P70/P75 and laptops/notebooks

S68X-2377-00 IBM Personal System/2 Model P70 Technical Reference Apr 1989
P70 Supplement for the Hardware Interface and BIOS Interface Technical Reference
DASD Storage Interface Specification Micro Channel (REV 2.2)

Planar BIOS
Floppy Drive
Floppy Drive Replacement
Support for 2.88MB Floppy Drives on New System Board FRU 56F9085
Supported Memory
The Mysterious "Masked SIMM" Revealed!

P70 Old System Board
   Old Video Card
P70 New System Board
   New Video Card

Disable ESDI Controller
   Derive MCA Bus from ESDI Ports?
Plasma Display Adapter Connector ("Display" on planar)
Plasma Connector Pinout
Plasma Display Auto-Dim Block Diagram
Remove P70 Floppy (H2)
ALPS DFP723D15C Rear PCB FP1T08D from a sick floppy
Remove Battery
Pointing Device Port (Not for KB!)
   305 Error at Power-Up
P70 Drive Carrier Mounting Hole Spacing
Auto 16/4 Token Ring Card Fits Lower Slot
113 Error
P70 Fixed Disk Drive Connector
Modify 160MB SCSI HD with ESDI PCB?
WD387 60MB Drive PCB
Fitting a SCSI hard drive
Early P70s Loose Configuration After Quick On-Off-On

For the original document, go to Dr Jim's P70 Project
   The P70 came in two planar versions: the older 38F4688/65X1564, used primarily in the 20 MHz -061 machines (but also seen in some -121 20 MHz boxes), and the 38F6973/56F9085 used in 16 MHz and 20 MHz -121 models.
   38F4688/65X1564 planars have the 386DX socket immediately to the right of the 387DX socket, and two BIOS ROMs near the upper left edge of the board. The 38F6973/56F9085 has the 386DX socket above and to the left of the 387DX socket. Another distinguishing feature of the newer models is the inclusion of video output filtering on the video card instead of on a 'daughter card' fitted in series with the video output cable. The newer planar seems slightly faster on some benchmarks, but the difference is hardly noteworthy.

Planar BIOS

New Planar (FRU 56F9085)

Single EPROM BIOS chip (128K x 8 CMOS EPROM - HN27C301G-20)
   56F7439.BIN P70 Planar BIOS

Old Planar (FRU 65X1564)

Two EPROM BIOS chips (64K x 8 CMOS EPROM - D27512-200V10)
   65X1565.BIN P70 Planar BIOS (odd)
   65X1566.BIN P70 Planar BIOS (even)

Floppy Drive

P70 comes with ALPS DFP723D15B 3.5" 1.44 MB floppy drive. FRU 38F5936

Floppy Drive Replacement

From Bob Eager:
   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.

Support for 2.88MB Floppy Drives on New System Board FRU 56F9085
  While desperately searching for a working drive, research turned up some assertions that the 2.88MB 64F4148 worked (Sony MP-F40W-00). The floppy header is on the correct side, the only downside is that the floppy eject button is about 1/8" too long to shut when a floppy is in the drive. Not a bad trade-off.

  I dunno, maybe the FDC Gate Array adds functionality to the NEC D72065L. But the new planar does support the 2.88MB under the original Refdisk (at what capacity I dunno). If you patch the original Refdisk with XGAOPT it updates some things...

End result is a choice for 2.88MB Diskette. Note that running autoconfiguration sets it to 1.44MB, but hey, it still works!

Supported Memory

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

Just like their big brother, the P70 prefers the Panasonic SIMM in SIMM2. 85 ns speed.

SIMM1: 65X6249
SIMM2: 65X1309/FRU 90X8625/iGH0258DA
SIMM3: 65X6249
SIMM4: 65X1309/FRU 90X8625/iGH0258DA

The Mysterious "Masked SIMM" Revealed!

2 MB 85 ns P/N 65X249 - FRU 92F0104

Thanks to Tim N Clarke for digging through his private stash. Notice the places for R1 and R2, yet there is no solder dots on the reverse for R3 and R4. Yet the multimeter shows OXOX (pins 67-68-69-70). From this, "masked" probably means the SIMM's PCB connects pin 68 internally, i.e. in the mask for the traces.

2 MB 85 ns FRU 90X8625 - P/N 65X1309 - iGH0258DA

This is an original Panasonic iGH0258DA. Not even markings for PD resistors. Yet the multimeter shows OXOX (pins 67-68-69-70). PD bit shunts are definitely part of the SIMM's PCB mask.

Note: the four white outlines under the big memory chips are SMD capacitors. If you look edge-wise at the SIMM against the light, you will see SMD caps under the big chips on BOTH sides..

Kingston KTM-2000/M70 Failures
The P75 will digest Kingston KTM-2000/M70 memory, but the late P70 planar wants nothing to do with it. When I was trying to snap a KTM-2000/M70 into the socket, it looked "bowed", it may be the center notch is not deep enough? I kept getting not properly seated as a possible cause.

But whether it was all KTM-2000/M70, or M70/IBM, it threw a 225.

Peter said:
   I cannot recall right from out of my head if the P70 reads all 4 bits of the PD signal or if it masks it down to the two important bits only. In this case certain 4MB modules might be detected as 2MB ... but end up in an error later during memory count.

P70 Old System Board FRU 65X1564

146818A MC146818A RTC
4464 NEC D4464G-15L
65 PN 65X1565
66 PN 65X1566
72065 NEC D72065L
8259A NEC D71059L
8042 IBM MPD80C42C-146
BAT 6v Battery
Bus 32 bit riser
Display 16 bit video
DMA 90X8134
Ext FDD Hosiden connector
F1 KB fuse "SOC 1A"
Fan Solder pads
Floppy 34 pin header
GA1 38F7800
GA2 65X1279
HDA Top 34 pin header
HDA Bottom 40 pin header
IND Indicator header
J1 Power On Password
J2 solder pads
J3 solder pads
J4 solder pads
KBD Keyboard header
Mouse Mouse header
PIO 72X8299
POS1-4 72 pin SIMMs
Printer DB25 port
PRT 94X1265
PSU Power header
RS-232C DB25 serial
SPK Speaker
Y1 32 KHz xtal
Y2 1.843 MHz osc
Y3 14.31 MHz osc
Y4 40.0000 MHz osc
Y5 32.0000 MHz osc

Old System Display Card FRU 38F4686

4146 Vidmem
CN4 26 pin header
CRT HDD port
OSC1 Unk
OSC2 Unk
JP1 Unk
JP2 Unk
JP3 Unk
JP4 Unk
JP5 Unknown

P70 New System Board FRU 56F9085

72065 NEC D72065L
8042 Outline, not populated
BAT 6v Battery
Bus 32 bit riser
CPU GA 33F5946
Display 16 bit video
DMAC 90X8134
Ext FDD Hosiden connector
Fan Solder pads
F1 KB fuse "SOC 1A"
F2 Fuse "SOC 3A"
FDC GA 33F8602
Floppy 34 pin header
HDA Top 34 pin header
BA Bottom 40 pin header
IND Indicator header
I/O GA 33F5838
J1 solder pads
J2 Power On Password
KBD Keyboard header
MC146818 MC146818AFN RTC
Memory Controller GA 33F5944
Mouse Mouse header
MS700 57X4111
NS16550 NS16550AFV
PAL 20L8 marked "ROM"
POS1-4 72 pin SIMMs
Printer DB25 port
PSU Power header
ROM P/N 56F7439
RS-232C DB25 serial
SPK Speaker
Y1 32.768 KHz xtal
Y2 14.31 MHz osc
Y3 24.000 MHz osc
Y4 40.0000 MHz osc

ROM is Hitachi HN27C301G-20, Datasheet

Thanks to Jay P. Thorne who went through the tedious process of pulling his P70 apart for the scans I used for the New System Board and New System Video Card.

Odd, the 8259As have been integrated into one of the Gate Arrays. The 8042 has also been integrated, but there is a 8042 PLCC outline to the right of the PS/2 mouse port. PRT has also disappeared.

New System Display Card FRU 38F4686

Arne Falch wrote:
By the way..: I have the new type of display card and plasma panel. Since the old display card will not work with new plasma panel (or vice versa), I guess that the old panel connections are different. The panel is a Matsushita electric type MD480T640PG4, P/N 38F4744. made in week 06,1990.

The machine is originally a model 8573-031 (16Mhz processor, 30MB disk), but someone has put in a 60Mb disk.

Disable ESDI Controller
>I will be surprised if it can be disabled. 

Peter said:
   Just remove the harddisk .... the ESDI controller is underside :-) These drives are drive and controller in one physical unit. The strange 2-connector port they are attached on the P70 is in fact a "sort of" MCA connector. The card-ID is DF9F and it will show up at slot 3 in the setup.

MCA Bus from ESDI Port?
> Can you hack an MCA bus out of the pseudo-one in the ESDI-DBA connector?

Ed Avis replies:
   I'm told that this is not possible because the connector carries only those signals needed for the disk, and not enough for a general MCA card.

Peter said:
   The VGA port supports all VGA graphics and text modes including 640 x 480 graphics, 320 x 200 graphics in 256 colors, and 720 x 400 text using any optional PS/2 VGA color display, and maintains compatibility with CGA and EGA modes. Unlike to the P75 the P70 cannot drive Plasma and external VGA at one time - except in DIAGS mode.

   As I said in a previous posting: the VGA chipset on the plasma-video adapter is the same 256K-IBM / INMOS stuff as used in the Mod. 50 / 60 / 70 / 80 - and therefore has the same limits: 640 x 480 at 16 colours ... ending of sending. So the answer is "No - you cannot get more colours at 640x480".

I'd really tried a lot to get more out of that thing (back in the good old days) but it simply doesn't work. The available memory on the bit-planes is too low. You need at least 512K VRAM (and a better Video DAC) but the Inmos-DAC *should* be able to get it - probably. It is specified for a video bandwidth of 18.44 Mhz only (which is 640 x 480 with 60 Hz vertical refresh) - but the main problem is the missing Video-BIOS mode for 256 colours at 640 x 480 and the missing V-RAM.

   Simple calculation: 640 x 480 pixels = 307.200 pixels total. Each one occupies 4 bit for 16 colours  = 153.600 bytes V-RAM (Video Mode 12h). The 320 x 200 / 256-colour mode (Mode 13h) occupies 8 bit per pixel and therefore a 256-colors mode would need double the space.
   The Video-DAC controls 4 x 64K for each "Map", where the maps are the bit-planes for red, green, blue and intensity on the 640 x 480 mode. The Video-DAC adress buffer resides at A000h - AFFFh (whereas the locations from A95FF - AFFF are "reserved").

   I really tried to write a video driver for this thing ... but it is hard to replace hardware with software - especially if you have the hardware missing to support that. :-D

>is possible to use the display card of a P/2 Model P70 in another PS/2 system with onboard VGA. I  don't want to use both screens in the same time. I do not want to use any CRT. I want to use the plasma screen on my PS/2 Model 55.

   As far as I can tell - you can't. The plasma board is basically a plain vanilla VGA card with a different output stage for the row/column addressing of a plasma display. But internally it uses the same chips, addresses and ports like the generic onboard VGA of the 55SX - apart from the odd form-factor of this card.
   The card-ID should be EDAF - but there is no ADF for this card. There is an @EDAF.DGS on the P70 reference and that means the ADF function is substituted by the board logic setup internally, so you cannot take it over anyway.

   The P70  / P75 have built-in information on this EDAF card and need no ADF then - the 55SX (and none of the "normal" PS/2 machines) hasn't. In addition you need the P70 power supply for the high voltages to run the plasma display.

Plasma Display Adapter Connector
The following figure shows the Signal assignment of the plasma display adapter connector. The connector contains the same signal set as of the 16-bit micro channel connector except two pins; the pin B04 does not provide the signal 14.3MHz OSC and the pin B45 is assigned with the signal -KEYSTROKE for the plasma display.

Pin Signal Pin Signal
B03 GND A 03 GND
B04 Reserved A04 A 11
B05 GND A05 A 10
B06 A 23 A06 A 09
B07 A 22 A07 +5Vdc
B08 A 21 A08 A 08
B09 GND A09 A 07
B10 A 20 A10 A06
B11 A 19 A11 + 5Vdc
B12 A 18 A12 A 05
B13 GND A13 A 04
B14 A 17 A14 A 03
B15 A 16 A15 + 5Vdc
B16 A 15 A16 A 02
B17 GND A17 A 01
B18 A 14 A18 A 00
B19 A 13 A19 + 12Vdc
B20 A 12 A20 -ADL
B22 -IRQ 09 A22 -BURST
B23 -IRQ 03 A23 -12Vdc
B24 -IRQ 04 A24 ARB 00
B25 GND A25 ARB 01
B26 -IRQ 05 A26 ARB 02
B27 -IRQ 06 A27 -12Vdc
B28 -IRQ 07 A28 ARB 03
B30 Reserved A30 -TC
B31 Reserved A31 +5Vdc
B32 –CHCK A32 -SO
B33 GND A33 -S1
B34 –CMD A34 M/-IO
B35 CHRDYRTN A35 + 12Vdc
B37 GND A37 D 00
B38 D 01 A38 D 02
B39 D 03 A39 + 5Vdc
B40 D 04 A40 D 05
B41 GND A41 D 06
B42 CHRESET A42 D 07
B43 Reserved A43 GND
B44 Reserved A44 -DS 16 RTN
B48 D 08 A48 + 5Vdc
B49 D 09 A49 D 10
B50 GND A50 D 11
B51 D 12 A51 D 13
B52 D 14 A52 + 12Vdc
B53 D 15 A53 Reserved
B54 GND A54 -S8HE
B55 -IRQ 10 A55 -CD DS 16
B56 -IRQ 11 A56 + 5Vdc
B57 -IRQ 12 A57 -IRQ 14
B58 GND A58 -IRQ 15

Plasma Display Connector

P70 Auto Dim Block Diagram
Auto-dim function
  The plasma display has an auto-dim function. It automatically turns the plasma display off after the specified period since the last keystroke. Any keystroke returns the plasma display on.
A desired value for the period can be specified approximately in the range 1 to 120 minutes during the system configuration by the backup copy of the reference diskette.

Note: For German models, the background intensity of the screen is selectable. The background intensity does not affect the auto-dim function.

The auto-dim logic is integrated in the PDC on the adapter card. (See Figure 4-3.)

The sequence of auto-dim operation is as follows. (See Figure 4-3.)
1. During the system configuration, plasma display may be enabled (PDP ENABLE bit is set) and a value corresponding to the specified period is stored.
2. When the auto-dim function is enabled. the AUTO-DIM ENABLE bit is set by POST (Power-on Self Test).
3. The up-counter increases each minute with a interval pulse derived from the VSYNC (Vertical Synchronization) signal.
4. The comparator compares the count and the value specified for the period, then the result is latched.
5. The result is gated twice into the plasma display.
If the AUTO-DIM ENABLE bit is set and the count has reached the matching value, the plasma display is disabled and the up-counter is reset. Otherwise, nothing is performed.
6. Go to step 3.

P70 Plasma Pinout

Arne Falch wrote:
   I used a scope on the connections, and I was able to identify pins for 4 databits, pixel clock, vertical and horizontal sync. There are still 2 or 3 unknown signal pins, one is probably a blanking or data enable pin.

Ok, here is my first try at the pinout.:

1    Vertical sync, active high. 15ms period, 62uS high pulse.
3    Horizontal sync, active low. 32 uS period, 3,8uS low pulse.
5    Pixel Data 
7    Pixel Data
9    Pixel Data
11  Pixel Data
13  Data Enable? Blanking? One long 8mS high pulse, then many  32uS period pulses, with  high time =  6.3uS. - then pattern repeats.
15 Display Data clock. approx  40nS period, my guess is frequency is the same as one of the Oscillators. (Ed. 4x10(8) inverse is 25MHz)
17  Display On/Off . Low signal = on. Goes high after 10 min display blanking timeout.
19  1,1mS low, 2,7mS high, 1,1mS low,  11 (eleven) ms high, then pattern repeats. (Blanking???.)
        Maybe the 1.1 mS periods is longer when the display is blanked at the top/bottom in CGA/EGA mode? I will look into this when I get software that enables CGA/EGA mode.
21  Unknown signal. No visible activity.
23   GND
25   GND

All even-numbered pins are GND.

Signal connections:
1    Pin 16 on 74LS241 via 330 ohm.
3    Pin 18 on 74LS241 via 330 ohm
5    38F461 (large IC)
7    38F461 (large IC)
9    38F461 (large IC)
11  38F461 (large IC)
13  38F461 (large IC)
15  38F461 (large IC) Goes to a pin with GND pins on both adjacent pins 
- this corresponds well with a clock signal.
17  38F461 (large IC) 
19  38F461 (large IC)
21   Unknown. No visible activity.
23  GND
25  GND

The connector corresponds CN1 on the drawing on your page. The machine is located elsewhere at the moment (at work), so the drawing is from memory. I will correct it if I'm wrong.

The display card, left edge, where the cable to the panel enters:

                            Top of machine.
  |        _____Pin 26 of display panel cable
  |      /     ____Pin 25 of display panel cable 
  |    o  o
  |    o  o           Three-pin capacitor??
  |    o  o             ( )    ( ) 
  |    o  o             ( )    ( )
  |    o  o             ( )    ( )
  |    o  o             ( )    ( )
  |    o  o             ( )    ( )
     Some 74LS logic over here
  |    o  o             ( )    ( )
  |    o  o             ( )    ( )
  |    o  o
  |    o  o
  |    o  o
  |    o  o___Pin 1 of display panel cable
  |     \________Pin 2 of display panel cable. 


                          MC edge connector

Remove Floppy (H1)  I have two -121s, one has the H1, the other has an H2.

Remove P70 Floppy (H2)


Open the plasma screen so you can get your hand behind it.Grasp the lower edge of the drive cover, pull out and forward. Once it snaps off (you will feel it, pull the cover up and out. If you grab onto the floppy slot, it should give you enough of a grip to do it.


   Unscrew the black screw at the bottom center of the drive carrier. If you look between the floppy cable and the grounding strap, you will see it. Thank God it's a captive screw. It's a combo standard/phillips screw.

  With the retaining screw loose, push the drive carrier up until it comes free of the case clips. Now you have full access to the floppy drive mounting screws.You must remove the floppy from the carrier before you can take the floppy cable out.

Install Drive Carrier
  Reverse action of removal.  Hook on case clips and pull down. When seated, screw in the black retaining screw in the bottom center. Now look at the sides of the drive carrier. Notice the slots about half way up the carrier- they go straight in, then go down. Look at the cover- it has two posts... slide the cover onto the carrier, make sure the eject button is lined up with the hole. Now push the cover down until it snaps into place. Congratulations, break out the Jolt!


The image is of the rear or bottom PCB from an ALPS DFP723D15C floppy drive, P/N 38F7802 FRU 38F5936. It is correctly oriented in the position it would be when installed, e.g. with the 34 pin header pointed down.

Not a fun day. Many of the solder joints in the lower left have a "grainy" look to them. Oddly enough, the power component in the lower left corner by J4 (floppy motor power) has green corrosion on BOTH sides. One would think if it was from a leaking cap, it would be toward the source of contamination.

At this point, I am hesitant to start recapping, due to the poor looking solder joints of a whole bunch of teeny tiny components. Heck, some SMD components have the grainy solder appearance looking almost as big as the component... Maybe a good application of baking soda and water could remove some of this, but I am not confident.

Remove Battery

   This shows how to remove the carrier and battery. To replace just the battery, pull the catch away from the battery, and pull the battery up. Battery is FRU 72X8498, and the common replacements are HERE Usually in the camera section of your local supermarket.

Pointing Device Port (or Mouse Port)
Peter says:
   The rear port is designed 'pointing device port' in users manual as well as HMM. No keyboard will work on this port ! Don't use a serial mouse to PS/2 port adapter! You may just end up frying something!

305 error at power up
   That is a sure indication that the keyboard/mouse port fuse is blown. If you open the unit and look at the lower side of the board down from the rear mouse port you will find a little black square fuse. "SOC 1A" printed in white on it. Maybe you need to bend the EMC (grounding) shield a bit up to see it. It is  marked F1 on the planar and surrounded with a box printed in white. (Left of the board fixing screw).

Check continuity with a multimeter. If it reads infinite resistance it is blown.

   To change it: no need to remove the entire board (and too complicated anyways). Just cut the fuse with a sharp pliers directly at the fuses' case and remove it. Bend the remaining contacts up and straighten them a bit. Get a new microfuse (resistor style fuses) and solder it to these contacts. Cut off the rest of the "legs" and that was it.

   If the fuse was *not* blown and the machine still has a working keyboard - suspect the mouse / mouse driver to be non-functional at all. Get a "real PS/2" mouse and use the MOUSE.COM from PC/MS DOS or the  MOUSE.EXE from Win95 (which is a Logitech-driver V 6.50)

  If you end up in a non-functional keyboard and no blown fuse ... well ... you'd damaged the keyboard / mouse controller, which cannot be replaced (that easy). In this case you should try getting a replacement system board.

P70 Drive Carrier Mounting Hole Spacing

   All dimensions are from the rear of the drive. They are to the center of the hole. Be careful when drilling! These placements DO NOT line up with the reinforced segments of the drive case. Be careful when tapping! Use a plug tap, a normal tap would bottom out on the PCB.
  The mounting holes do NOT line up with ANY holes on modern drives, even the 0661 drive holes WILL NOT FIT. The drive will mount upside down, there is no other way to do it.

       Additional features of the system unit include: 
o   One general purpose 32-bit full-length Micro Channel slot* 
o   Half-length Micro Channel slot
o   85-watt automatic voltage-sensing power supply 
o   Time and date clock with battery backup 
o   Integrated 16-grayscale plasma display, integrated version of IBM Enhanced PC Keyboard. 
*  Some half-length cards that fit in a half-length slot may not fit in a full-length slot. 

Auto 16/4 Token Ring Fits Lower Slot
> the Auto 16/4 Token Ring fits into the bottom 16 bit slot, almost like it was built for it.

Peter has a flashback and says:
   The short 4Mbit on which the later 16/4 short design is based on *was* in fact particularly designed for the P70 ... some time back in the late 80s when the P70 (and the P75) appeared in IBMs list there was a "short Token Ring card" offered along with it, while the "normal PS/2" still got the "toilet-seat 4 Mbit TR card".

       The Token-Ring Network Model P70 386 Adapter/A (#1598) permits attachment of the Model P70 386 (8573-061 and 8573-121) to the IBM Token-Ring Network.  This adapter is half-length and designed to fit in the short slot.  It transmits and receives at four million bits per second.  To facilitate attachment to the IBM Personal System/2 P70 386, a unique L angle connector with a permanently attached short cable is provided. 

8573-031 30 MB Hard Disk, 16 MHz planar 
8573-061 60 MB Hard Disk, 20 MHz planar 
8573-121 120 MB Hard Disk, 20 MHz 

113 Error

This error code indicates a DMA timeout caused by a MCA card... if there is nothing installed except the harddisk - replace that. It doesn't look like one, but the 72-pin card-edge connector is in fact a MCA connector (Slot 4 in the setup).

> As noted in a different thread: some series of 120 and 160MB HDs did not run properly when installed "upside down" in the P70. Either they come up with a 10482 error right after start -or- fail to LLFormat / run at all later but operate fine otherwise when turned "upside up" again. (WD-3158, WD-3160).

>> The -031 models used the infamous "energy conserving" harddisk, which reduced spindle speed when in idle and spins up again when accessed. A nerve killer !

> Like the Model 50Z and 70 the P70 had fairly lot of problems with non-functional HDs. In the P70 *only* the black IBM WD-series drives had been used for the 60 and 120MB models - like the WD-3158 120MB drive from the Model 70-121 / -A21.

P70 Fixed Disk Drive Connector

The following figure shows the signal assignment and pin numbering for the fixed disk drive connector on the adapter. The fixed disk drive connector is a 2- by 36-pin connector. Side A of the connector is the top and Side B is the bottom.

Ed. HDA Upper (34 pin) and BA Lower (40 pin). So... we have 74 pins from the headers, or so it seems. If lucky, the Upper and Lower headers are Signal and Ground...

Side A Side B
Pin I/O Signal Pin I/O Signal
1 0 -CD SETUP 1 0 A15
2 0 A13 2 0 A14
3 N/A Ground 3 N/A Ground
4 0 A11 4 N/A Reserved
5 0 A10 5 N/A Ground
6 0 A09 6 0 A12
7 0 +5Vdc 7 0 -CMD
8 0 A08 8 I -CD SFDBK
9 0 A07 9 N/A Ground
10 0 A06 10 I/O D01
11 N/A Ground 11 I/O D03
12 0 A05 12 I/O D04
13 0 A04 13 N/A Ground
14 0 A03 14 0 CHRESET
15 0 +5Vdc 15 I/O D08
16 0 A02 16 I/O D09
17 0 A01 17 N/A Ground
18 0 A00 18 I/O D12
19 0 + 12 Vdc 19 I/O D14
20 0 -ADL 20 I/O D15
21 I -PREEMPT 21 N/A Ground
22 I -BURST 22 I/O D00
23 0 +5Vdc 23 I/O D02
24 I ARB 00 24 I/O D05
25 I ARB 01 25 N/A Ground
26 I ARB 02 26 I/O D06
27 N/A +12Vdc 27 I/O D07
28 I ARB 03 28 I/O D10
29 0 ARB/-GNT 29 N/A Ground
30 0 –TC 30 I/O D11
31 N/A +5Vdc 31 I/O D13
32 0 -S0 32 0 -SBHE
33 0 -S1 33 N/A Ground
34 0 M/-IO 34 I -CD DS 16
35 N/A Ground 35 I -IRQ 14
36 I CD CHRDY 36 N/A Ground

Modifying 160MB SCSI Drive With ESDI PCB

   Modifying a 160 MB SCSI Disk was only half way successful (took of the SCSI PCB and hooked up the ESDI PCB from my bad 120 MB Drive). I can see the HD when booting with the Refdisk, but I get all kinds of errors when trying to format it.

   The 160 operates with a different number of sectors IIRC. Only have the data for the 80 and 160MB: 984 cylinders, 10 heads, 17 (80) and 34 (160) sectors. So the 120 must have 26 sectors (25.5 arithmetically - but there are no half cylinders ...). I think the 120MB controller cannot "fetch" a valid sector start ... and therefore jumps out. The LLFORMAT routine does not go *that* deep that it can write raw sectors on the media. That's usually the purpose of some factory tools.

WD387 60MB PCB

D15 - LED
J4 - 7x2 pin header with two pins snipped
J7 - two pin header
J2 - 20 pin header
U3 - 32P541-CH
U5 - S80C31-1
U7 - K1-230 BIOS?
- Hitachi HD64950CPB
U17 - HM6264ALFP-15T
U9 - TC8564AF
U11 - TC17G032AF 6127911
U15 - P/N 6127914
Y1 - 16KSS0A
Y2 - 12AKSS0A
Y3 - 3.6DKSS0B

S80C31-12 Temic Semiconductors 8-Bit Microcontroller-Microcomputer - Programmable serial port
HD64950SCP Hard Disk Controller - File Data Processor
Silicon Systems SSI32P541-CH Read Data Processor Datasheet


79F6265 BIOS
38F7621 / M52831FP
D240B1 osc

79F6265 BIOS chip is a SOIC 28 like on the P75 planar...

80196KB CHMOS Microcontroller
32D535 Data Synchronizer / 2, 7 RLL ENDEC with Write Precompensation
32P541 Read Data Processor
M5M5256BFP 32K word by 8-bit CMOS Static RAM
65256BLFP Hitachi
TA7736P Brushless, Multi-Phase dc Motor Driver

Fitting a SCSI hard drive

From Bob Eager:
   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 which 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:

  1. 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.
  2. 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.
  3. 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).
  4. 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.
  5. 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).
  6. 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.
  7. Boot from the reference disk and run auto-configuration. Run diagnostic tests, and with luck that will be it!

Early P70s Fail to Retain Configuration after Quick "On-Off-On"

>> DASDDRVR.SYS under DOS. Early P70 (16MHz version) tend to "spit out" the configuration when you quickly power them off and back on. 

>Not only the 16 MHz ones. I had this phenomenon on my 20 MHz Rev.1 (which is up and running again) also. Seems a common phenomenon for the first PS/2 - which lacked a delay in the power supply. But the early 16MHz and all Mod. 60 were pretty critical. If you didn't wait at least 20 seconds after a power down you could have wrecked the config already.

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Ardent Tool of Capitalism - MAD Edition! is maintained by Tomáš Slavotínek.
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