Walkom NP-903

This unbranded i386SX laptop from 1991 is a clone of the more common MicroStar (MSI) NoteStar NP-903. 



Technical specifications:

CPU: Intel i386SX 16MHz
RAM: 2MB
Graphic: Chips & Technologies 82C456 VGA Controller
Chipset: Headland Technology, Inc. HT21
IDE / Floppy controller: Acer M5105
Floppy: Citizen U0DA-19A



Mainboard


Power Supply


Test Reviews

Remark: According to Wikipedia Modern Computer is another Product line of MicroStar.

Upgrades

  • RTC clock Dallas DS1287: 
    • modern replacement: nwX287 by Necroware (changeable battery) 
  • Math Co-Processor: Cyrix FasMath 83S87 (fastest of the 387SX compatible coprocessors)

  • RAM Upgrade from 2MB to 4MB
  • Harddisk CF Compact Flash 2.5" 44Pin, 2mm, IDE Converter 
     

Repairs

Floppy drive

If the floppy drive makes loud noises when the disk is accessed and nothing can be read, it is a good idea to perform these steps:
  • replace the drive belt (is compatible to the Citizen U0DA-02A, which you can find on ebay)
  • clean the read heads with isopropyl (alcohol)

Ribbon cable

Due to age (contacts tend to break), the keyboard and power control cables should be replaced:
  • Keyboard: 10 Pin, 1.25mm Pitch, 100mm length, reverse
  • Power control & LED: 20 Pin, 1.25mm Pitch, 100mm length, forward

Operating System

Prepare the CF card

The maximum harddisk size this machine can address is 504MB (16 heads, 63 sectors per track, 1024 cylinders) and therefore we need to prepare the 4GB CF card:
  • use 86Box (x86 Emulation), add a harddrive and set it to a maximum of 504MB (PreSet selection)
  • insert the boot image of FreeDos / MS-DOS and let the OS take care of partitioning and formatting
  • use the created img file in Rufus to write it to the CF disk

MS-DOS 6.22 with Windows 3.11





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