PB286 And IS/VT286 Upgrade Information

Caution

Only authorized service personnel should upgrade the system. Anyone who wants to upgrade the system themselves should know about the dangers of ESD (Electro-Static Discharge) and the necessary precautions. Unknowingly zapping the components of the computer will void the warranty.

Memory
There are two versions of this motherboard. The old motherboard is known as the ISVT286.
New Motherboard (PB286)

Note

1. Upgradeable to 1MB by adding (4)256Kx4 and (2)256Kx1

2. If you want to install Memory Card(s), in your 1 MB RAM system, be sure to select SW1-1 ON, SW1-2 OFF.

        ╔═════╤══════╤═════════╤═════════════════╗
        ║SW1-1│ SW1-2│ RAM Size│ MEMORY SETTINGS ║
        ║     │      │         ├──────┬──────────╢
        ║     │      │ SELECTED│ BASE │ EXTENDED ║
        ╠═════╪══════╪═════════╪══════╪══════════╣
        ║OFF  │ OFF  │ 256KB   │ 256  │ 0        ║
        ║OFF  │ ON   │ 512KB   │ 512  │ 0        ║
        ║ON   │ OFF  │ 640KB   │ 640  │ 0        ║
        ║ON   │ ON   │ 1 MB    │ 640  │ 384      ║
        ╚═════╧══════╧═════════╧══════╧══════════╝

Old Motherboard (ISVT286)
Note

1. Replace 64K DRAM's with 256K DRAM's to upgrade to 1 MB.

2. 1MB RAM must be split 512 Base/512 Extended.

3. If 640k base is required with extended memory, add a memory card.

        ╔══════════════════════╤═════════════════╗
        ║J2 (RAM Select Jumper)│ MEMORY SETTINGS ║
        ╠═════╤════════════════╪══════╤══════════╣
        ║PINS │MODE (RAM Size) │ BASE │ EXTENDED ║
        ╟─────┼────────────────┼──────┼──────────╢
        ║1-2  │1 MB Mode       │ 512  │ 512      ║
        ╟─────┼────────────────┼──────┼──────────╢
        ║2-3  │640 Mode        │ 512  │ 0  OR    ║
        ║     │                │ 640  │ 0        ║
        ╚═════╧════════════════╧══════╧══════════╝

Math CO-Processor
A math co-processor can be installed in U99, no jumpers need to be changed. Use a: 80287-6 for 6-8-10 MHz systems 80287-8 for 12 MHz systems,

┌──────────────────────────────────────────────╥───╥──────────────────────┐
│                                           J1 ╙───╜  ┌────┐              │
│                                                 ┌──┐└────┘     ┌─┐      │
│ ┌─┐  ┌─┐  ┌─┐  ┌─┐  ┌─┐  ┌─┐  ┌─┐  ┌─┐ ┌─┐┌─┐   │S │    ┌─┐    │ │      │
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ ││ │J▒ │W │    │ │    │ │      │
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ ││ │2▒ │1 │    │ │    └─┘      │
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ └─┘└─┘   │  │    └─┘ ║▓       ┌─┐│
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│          └──┘┌─┐ ┌─┐ ║▓       │ ││
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ ┌─┐  ┌─┐ ┌─┐ │ │ │ │ ║▓ ┌─┐┌─┐│ ││
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ │  │ │ │ │ │ │ │ │ ║▓ │ ││ │└─┘│
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ │  │ │ │ │ └─┘ └─┘ ║▓ │ ││ │┌─┐│
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ └─┘  └─┘ └─┘         ║▓ └─┘└─┘│ ││
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│                      ║▓       │ ││
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ ┌─┐ ╔═══╗┌─┐ ┌───┐            └─┘│
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ │ ║   ║│ │ │   │      ┌─┐┌─┐┌─┐│
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ │ │ ║   ║│ │ │   │ ┌───┐│ ││ ││ ││
│ │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│  │▓│ └─┘ ║ U ║└─┘ │ U │ │   ││ ││ ││ ││
│ └─┘  ├─┤  ├─┤  ├─┤  └─┘  └─┘  ├─┤  ├─┤     ║ 9 ║    │ 8 │ │ U │└─┘└─┘└─┘│
│      │▓│  │▓│  │▓│            │▓│  │▓│ ┌─┐ ║ 9 ║┌─┐ │ 1 │ │ 6 │┌─┐┌─┐┌─┐│
│      │▓│  │▓│  │▓│            │▓│  │▓│ │ │ ║   ║│ │ │   │ │ 8 ││ ││ ││ ││
│      │▓│  │▓│  │▓│            │▓│  │▓│ │ │ ║   ║│ │ │   │ │   ││ ││ ││ ││
│      │▓│  │▓│  │▓│            │▓│  │▓│ └─┘ ╚═══╝└─┘ └───┘ └───┘└─┘└─┘└─┘│
│      │▓│  │▓│  │▓│            │▓│  │▓│          ┌─┐ ┌─┐ ┌─┐    ┌─┐┌─┐┌─┐│
│      │▓│  │▓│  │▓│ ┌─┐        │▓│  │▓│          │O│ │O│ │ │    │ ││ ││ ││
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Cache Memory
This system does not support cache memory.

Video Memory
This system has a video card, upgrade depends on card.