PC720
Type 6860

720r101.exe PC720 Reference Diskette v1.01
720d101.exe PC720 Diagnostic Diskette v1.01
720u101.exe PC720 Utility Diskette v1.01
720s101.exe PC720 Support Diskette v1.01
pc720sp.lzh Pentium ODP Flash update for PC720 6860 v1.10
6860ref.lzh Reference Diskette for Pentium ODP 6860 v1.10
6860dig.lzh Diagnostic Diskette for Pentium ODP 6860 v1.11

PC720 PCI/Micro Channel Product Page (6860-J4x/J0x/JZG)
PC720 PCI/ISA Product Page (6869-J4x)
PC720/750 PCI/Micro Channel Product Page (6860-J4G/J0x/JZG, 6886-J04)
PC330/720/750 PCI/ISA Product Page (6873, 6863, 6883-JFx/JAP/JTN, 6887-JSx/J8x)
   Official Japanese product pages (archived).

1995 IBM PC Series 720: Unboxing (coobird's lab, YouTube)
1995 IBM PC Series 720: Looking inside (coobird's lab, YouTube)

Introduction
Models
Planar
Jumpers
CPU
Memory
L2 Cache
Video
Small PCI
Hard Drive Interface
Riser Card
2-Slot PCMCIA Adapter
Power Supply
CD-ROM
Service Partition

Content created by Sandy. Modified by Major Tom.


Introduction

PC720 6860 was introduced to the market together with PC750 6886 in 1995. 6860 is not a Pentium based PC. IBM Japan didn't introduce PC730 6876 in Japan, instead they made this unique space-saving desktop model. PC720 6860 is a strange *hybrid* PC with one MCA slot, one shared MCA/PCI slot, and a ISA-like slot for PCMCIA /A exclusively designed for this box.


Models

Model PC720 6860
J4G J00 J04 J08 JZG
CPU iDX4-100 i486DX2-66
L2 Cache 128KB None (Socket is omitted)
RAM (std/max) 8MB (Max 128MB, 32MB x4) 4MB (128)
VRAM 2MB 1MB (Upgradable to 2MB)
FDD 3-Mode (1.44MB/1.2MB/720KB) x1
HDD 728MB 540MB
Video S3 Vision864 PS/55 D/A NI
Option Slot PCI or MCA x1, MCA x1 MCA x2
Small PCI NIC TokenRing Ethernet
PC Card Slot Type I/II x2 or Type III x1 (ISA style PCMCIA /A)
Dimension (mm) 360 (W) x 370 (D) x 89 (H), 9 kg
Pre-installed OS PC DOS J6.3/V, Windows J3.1 DOS J5.02Z

Type JZG was equipped with a PS/55 Display Adapter/NI-J and DOS J5.02Z (JDOS).
Model 6869 is an ISA version of PC720.
Model 6863 (also ISA) is named as "PC720" but it's a Pentium machine with P-100.
6863 uses same planar with PC750 model 6883 (probably sold only in Japan, planar is different from that of 6885/6886 or 6887).


6860/6869 Planar (DX4-100 model) FRU P/N 85G7310, P/N 85G7235

J1 FDD Connector
J2 IR/PCMCIA
J5 Power Switch
J11 PSU connector
J12 PSU connector
J14 CPU Select (SX/DX)
J19 Unknown (default 1-2)
J20 PSU connector (Power Good?)
J22 FAN (Solder pads only)
J23 L2 Cache Socket (DX4 models only)
J24 Riser slot
J26 Small PCI slot #1
J27 Pads for Small PCI slot #2
J32 Speaker connector
J34 Volume pot connector
J36 Suspend/Resume connector
J37 Power & HDD LED connector
J38? CR2032 battery holder
J42 Pads for 4-pin jumper
J44 VESA connector
J50 Frequency select (66/50 MHz)
J51 Mouse Enable/Disable
J52 FDD write Enable/Disable
J53 Clear CMOS (1-2: normal, 2-3: clear)
J54 Password Overwrite
J55 CPU voltage select
U7 Socket 3
U16 PC87323VULB Super I/O
U18 M33s0570-013 OKI/06H3669 IBM
U24 85G7319
U40 Unknown (heatsinked)
U41 86C864P4 S3 Vision864
U42 Unknown (heatsinked)
U45 AvaSem AV9154-? CPU Freq. Gen.?
U53 86C716MG S3 SDAC
U55,56 DRAM sockets (video)
U57,60 KM416C256BJ-6 256Kx16 DRAM (video)
Y4 osc/xtal for U45?

J2 is silk screened as "IR/PCMCIA". It's obvious that PCMCIA is meant for a 2nd PCMCIA device which could be installed at the front end. I've believed for a long time that IBM only planned to develop such a device, and that they never made it. That was until I got my 6869-J4K (ISA DX4-100 model which is not listed in my PC Guide Book). J4K has additional PCMCIA slot just below the FDD bay which you can see in the picture at the top of this page. And what does "IR" mean? It's likely for some sort of IrDA device. No clue if it was ever released for the PC720.

J14 CPU type select
For 486DX set jumper to position 2-3 (default).
For 486SX set jumper to position 1-2.

J50 Output frequency select for programmable IC? (huh?) 1-2: 50, 2-3: 60.

J51-54 Default setting for these jumpers are all 1-2 closed.

J55 CPU voltage select
For 5V CPU close 2x3 jumper blocks near to the PSU connector.
For 3.3V CPU close 2x3 jumper blocks near to the CPU socket.


CPU

Planar can take a DX2-66, DX4-100 or PODP5V83. No interposer required to use 3.3V CPU's. In order to use PODP, BIOS should be updated to KOJT66JP. See below.

PODP

The PODP Support Diskettes Kit consists of 3 parts:

  1. 6860ref.lzh Reference Diskette Ver. 1.10
  2. 6860diag.lzh Diagnostic Diskette Ver 1.11
  3. PC720SP.lzh System ROM update utility Ver. 1.10A (KOJT66JP)

Note: Win95 support program, win95serv0.exe (dead), is not for 6860 but for 6863/6869 and other ISA models. 32bit PCMCIA driver contained in this archived file is not usable on 6860. It's for 6863/6869 (and it may be for Win95A).


Memory

The planar has 4 SIMM slots and takes 4, 8, 16, or 32 MB, 70 ns, FP, parity modules.


L2 Cache

Uses the same style 128-pin L2 cache modules as the Lacuna and 9585 K/N.

The original module is P/N 85G4865, marked as "128KB L2 Super Cache". This module can be used for M70/80 PowerBoard. To say the truth I bought my 1st 6860 in order to get the cache module from it.

The DX2-66 model does not have the cache socket.


Video

S3 Vision864 1 MB (2 MB for J4G model). Win95 recognize the chip with it's built-in driver.

JZG model doesn't use onboard S3 Vision but use a PS/55 Display Adapter/NI-J together with pre-installed DOS J5.02/Z (specialized DOS J5.02 for this model).


Small PCI

I've never seen this type of connector in any other PC. IBM Japan made only 2 adapters for this interface:

  1. SFF PCI Ethernet card, C/R 85G4854, equipped in 6860-J08 [P]
  2. SFF PCI TokenRing card, C/R?, equipped in 6860-J04. I want to see it!

Note: I don't know if it's a world-wide standard or not, but according to my friend, this connector was introduced as "kogata PCI" in IBM's leaflet issued when the PC720 was announced. In Japanese, "kogata" stands for "small" rather than "micro", though these two words are nearly the same.


Hard Drive Interface

Only one IDE channel is provided. There are solder pads for 2nd IDE channel on the planar, but even if the 2nd channel could be activated, there is no room for 3rd IDE drive.
The drive interface is EIDE and it can handle drives larger than 524 MB. I've used a 2.4 GB drive, and a 6.4 GB Seagate drive with 15 heads. Both worked well. I've also tried a 8 GB Seagate drive, but it wouldn't detect it.

Hard drive runs in MS-DOS Compatibility Mode Under Win95

Win95 will load "standard IDE/ESDI hard disk controller" with configuration #1 which has IRQ value fixed to 15. Change the configuration to #0 which has IRQ 14, all drives will work properly.


Riser Card FRU P/N 85G7333, P/N 85G2105?

All models other than JZG use same Riser Card which has PCI/MCA shared slot x1, MCA slot x1 and one ISA style slot for 2Slot PCMCIA/A (P/N 54G0547). Riser Card for JZG doesn't have a PCI slot but it has one more MCA bus slot for PS/55 Display Adapter /J which locates under connector J6 (opposite side of PCI slot J5). I'm not sure but probably J1 is for Enable/Disable selector for PS/55 display adapter. Outline below is the one for models other than -JZG.

Riser Front

J3,4 32-bit MCA slot
J5 32-bit PCI slot
U6 06H5423 (blue translucent QFP)
U8 10G7808 DMA Controller
Y1 24.0000 MHz osc

Riser Back

J1 Video /A selector? (default 1-2)
J2 Battery connector (CR2032?)
J6 ISA-style slot for PCMCIA /A
J9 PSU connector
U15 M91S028AT OKI/06H6468
U16 06H4542
U17 LH5168N-10L 8Kx8 SRAM (NVRAM?)


2-Slot PCMCIA Adapter FRU P/N 85G7334 [P]

U1 54G0574

2 slot PCMCIA /A with ISA style connector is equipped in all models. ISA models (6869 and 6883) also use same adapter.

Win95 built in driver can't handle this adapter properly on MCA models but the very same adapter installed in ISA models can be used without any problem under Win95B or Win98. I tested a driver for Win3.1 "PC Card Director" on my 6860-J4G and I found it could handle modem card. I've been using a 28.8Kb Double Jack Modem Card under Win95B. PCMCIA device is not seen under Device Manager, but the card securely detected in PC Card Director. I don't know if other cards such as NICs or SCSI PCMCIA can be used.


Power Supply

6860 has a very unique PSU. The cooling fan will slow down if the total system power is lower than 50W, and will stop to spinning completely if bellow 30W. Thus the cooling fan usually stays idle. When I got the 6860 I've immediately noticed that the fan wasn't running at all. As I didn't know about this unique feature I thought there must be some fault on the circuit board of the PSU. I disassembled PSU and soldered 12V line directly to the fan assembly. Only latter on have I learned about this unique function. The jumper wire is still there... Some machines have input AC voltage selector. Mine has a "fan mode selector", summer mode with direct connection and winter mode with original connection.

Mine works fine under DOS. But under Win95B it usually freeze at start up after the Win95 logo appears on the screen. I solved this symptom by modifying MSDOS.SYS to have a start up menu with default boot for Win95 after 60 seconds of delay time to boot. Maybe mine needs some delay for stable DC output for planar, a hard drive and a CD-ROM. I'm sure that this symptom is not related to the above mentioned fan cable modification, 'cause I have the same problem even when I switch back to the original cable connection.

Power Consumption

Maximum: 70 W
Typical: 40 W


CD-ROM

A genuine optional 2x speed CD-ROM (you can see it in the picture at the top of this page) is # 85G7285. I have a 4x slim drive for Toshiba laptops.


Service Partition

6860 is not an IML machine, but it does support service partition (reference partition?). My 6860 takes long time till the "Set Configuration" page comes on the screen when I boot the system with the Reference Diskette. It stays quiet while it reads configuration files as if the system froze. But from service partition stored on the hard drive it goes straight into configuration menu.

Content created and/or collected by:
Louis Ohland, Peter Wendt, David Beem, William Walsh, 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: 10 Aug 2022 - Changes & Credits | Legal Info & Contact