PC730/750
Types 6875, 6876, 6885, 6886

n2mt28a.exe Refference Disk for PCI/MCA models
n2jt50a.exe Flash Update utility (readme)
n2jt52a.exe Flash Update utility (readme)
Official Product Page and Software and Device Drivers (both dead)

PC 730/750 Planar
Jumper Settings
Memory
Video
CPU Upgrade
IDE Controller and Win95
BIOS may not recognize HD > 4.2GB
What to do if wrong BIOS Flash applied
Unplug Power Before Removing the HDD Cage


PC 730/750 Planar (Pentium 75/90/100/120/133 MHz)


(Outline borrowed from IBM manual)

1 Riser connector
2 (J15) Modem Ring Detect connector
3 (J29/WP) Diskette drive write protect
4 Diskette drive connector
5 HDD connectors (0: Prim, 1: Sec)
6 (J38) On/Off Switch PSU connector
7 (J37) On/Off Switch connector
8 Power supply connectors
9 L2 Cache size jumpers
10 Processor connector
11 (J19) Bus/Core Ratio
12 Cache connectors
13 Memory connectors (Bank 2)
14 Memory connectors (Bank 1)
15 Memory connectors (Bank 3)
16 Video memory connectors
17 (J40/PWD) Power-on password jumper
18 Battery
19 Display connector
20 Parallel connector
21 Serial connector
22 Serial connector
23 Mouse connector
24 Keyboard connector
25 Audio jack (Input jack)
26 Audio jack (Output jack)
27 IDE CD-ROM audio connector
28 (J28) Mouse jumper
29 (J26/J27) Bus/CPU speed select
30 Hard Disk (1-2) / Power LED (3-4)
31 Fan Header
32 Front-Panel (Audio)
33 Speaker (3-4)
34 Power Connector
35 Mute (Audio)
36 Mute (Audio)
37 AUX1 (CD-ROM)


Jumper Settings

The jumper setting information

Jumper Setting Description
J19 Open
Short
2/3 Bus/Core Ratio
1/2 Bus/Core Ratio
J28 1-2
2-3
Mouse enabled
Mouse disabled
J29
(WP)
2-3
1-2
Enable writing to a diskette
Disable writing to a diskette.
J40
(PWD)
1-2
2-3
Password enabled.
Password reset.
RED is default.

Bus/CPU Speed MHz Setting

Jumper 50/75 60/90
60/120
66/100
66/133
J26 2-3 2-3 1-2
J27 2-3 1-2 1-2

Cache Jumper Settings

Cache J21 J22 J23 J24
256 KB 1-2 1-2 1-2 1-2
512 KB *1 1-2 1-2 2-3 2-3
1 MB *2 2-3 2-3 2-3 2-3
Never seen a 512KB or 1MB cache module.

*1 Option Guide doesn't mention about 512KB setting.
It's written in Product Index stored in IBM WEB Site.
*2 TAG RAM: Socket #10 is vacant for stock 256KB configuration. According to the manual, one more TAG RAM should be installed in socket #10 for 1MB cache configuration.

Originally 8x cache chips are installed in socket 2 to 9. Each cache chips should be installed like illustrated on the picture.


Memory

You can use 32MB 60 ns/70 ns Parity SIMMs.
6885 ( PCI/ISA version ) can take EDO SIMMs but I have not tested EDO on mine.
Sander Fransen wrote in his page that 6863 could take EDO SIMMs. 6886 could do that too.
Watch SIMM socket layout. BANK 1 sockets are the two in the middle (#14 in the layout picture above).


Video

Onboard video chip is S3 Vision 868. Video Disable jumper is not ready on the planar. If you want to use a PCI video card under Windows 95, disable S3 video under Device Manager section of the Control Panel.

PCI Video card known to be usable on this machine:
   S3 Virge DX4 based card
   Matrox Mystique
   Matrox Millenium
   Matrox Millenium II


CPU Upgrade

The Planar itself supports Classic Pentium CPUs rated up to 133 MHz. VRM socket is not ready on the Planar. In order to use CPU rated higher than 133 MHz, you need an interposer. For MMX CPU, you need an interposer with a voltage regulator. K6-II/III-400 can be used with an appropriate interposer. PowerLeap interposer is my favorite one. Connect the power connectors FIRMLY or your interposer (and your K6 CPU) will get toasted (Ed. really?).

I've tested following CPUs and all of them worked nicely on an PowerLeap Interposer (PL-ProMMX Plus):

  • MMX166 and 233
  • K6-300
  • K6-II/400
  • K6-III/366 and 400

K6-III series require PL K6-III, PL-ProMMX Plus doesn't work (for me).

AMDK6UPD.EXE is required to use K6-2/350 or faster on Windows 95B/95C (OSR2/2.1/2.5). Japanese explanation is HERE.
Also refer to Knowledge Base Q-235249 if you use MS Backup.

For Japanese readers:
   PKK6.ZIP IO DATA PK-K6H series support software Ver. 1.02
   HK6_2.EXE BUFFALO (known as Melco) HK6 series cache utility diskette (1.44MB)


IDE Controller and Win95

The OPTI Dual PCI IDE Controller may not get properly recognized under Win95.
This symptom observed on some 6885 and 6886 ( not on every machines ). To solve this problem you need to rewrite Win95 system registry by following steps. This instruction was once available in OPTI's web site.

  1. From Windows 95 click Start
  2. Click Run
  3. Type in "regedit"
  4. Click OK
  5. Double Click HKEY_LOCAL_MACHINE
  6. Double Click System
  7. Double Click CurrentControlSet
  8. Double Click Services
  9. Double Click VxD
  10. Double Click IOS
  11. Double Click NoIDE 01
  12. Change the value to 00
  13. Close regedit
  14. Restart the system 1) From Start > Run execute with file name

If you get into the trouble at the final stage of installation and Win95 breaks into blue screen and the system can not go further to complete installation. then choose safe mode operation to do above modification. Hit F8 key to get boot menu so that you can select Safe Mode operation. Once the system get booted in safe mode, you can apply above mentioned steps. In some case Win95 may be installed properly without above error. Don't know why.


BIOS may not recognize HD > 4.2GB

If the drive is larger than 4.2GB and it's a 16 Heads logical drive, BIOS can't recognize it properly. EZDRIVE may help you...

If the drive is a 15 Heads logical drive, then you can use 6GB drive (I suppose 8 .4G is it's limit but these days there are no such 8G drives with 15 heads). I've used a Seagate 6.4G drive without Seagate Disk Wizard utility.


What to do if wrong BIOS Flash applied

I myself have not examined but it was reported to the news group 2 or 3 years ago.

If you applied wrong BIOS version for 6885 PCI/ISA system on your 6886/6876, you need a BUS Riser card for 6885. Install PCI/ISA BUS Riser on your 6886 and once configure it as a PCI/ISA system. Then apply CORRECT BIOS FLASH program (N2JT50A). Pull out the PCI/ISA Riser and change it to original PCI/MCA riser card.


Unplug Power Before Removing the HDD Cage

Important: Unplug the AC power cable from AC inlet connector before removing the HD structure from the box!
The system board and the Riser card are "alive" even if the main power is "OFF" and the AC power plug is connected to the wall outlet (I mean DC current is supplied always even though the main power SW pushed off). If the metal structure touches the solder side of the riser card, the riser will get damaged very easily. So again, Please Take my Advice. I fried 2 riser cards already (6885 PCI/ISA). After that I affixed a sheet of vinyl onto side wall of HD structure facing to the solder side of the riser.

Content created and/or collected by:
Louis Ohland, Peter Wendt, William Walsh, David Beem, Tatsuo Sunagawa, Jim Shorney, Tim Clarke, Kevin Bowling, Tomáš Slavotínek, and many others.

Ardent Tool of Capitalism - MAD Edition! is maintained by Tomáš Slavotínek.
Last update: 19 Nov 2021 - Changes & Credits | Legal Info & Contact