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Archive for February 23rd, 2014

Commodore VIC-20 (USA/NTSC Version) Boxed

February 23rd, 2014 No comments
Commodore VIC-20 USA (Boxed)

Autopsy:

The VIC-20 (Germany: VC-20; Japan: VIC-1001) is an 8-bit home computer which was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore’s first personal computer, the PET. The VIC-20 was the first computer of any description to sell one million units.

The VIC-20 was intended to be more economical than the PET computer. It was equipped with only 5 kB of RAM (of this, only 3.5 KB were available to the BASIC programmer) and used the same MOS 6502 CPU as the PET. The VIC-20′s video chip, the MOS Technology VIC, was a general-purpose color video chip designed by Al Charpentier in 1977 and intended for use in inexpensive display terminals and game consoles, but Commodore could not find a market for the chip. As the Apple II gained momentum with the advent of VisiCalc in 1979, Jack Tramiel wanted a product that would compete in the same segment, to be presented at the January 1980 CES. For this reason Chuck Peddle and Bill Seiler started to design a computer named TOI (The Other Intellect).

The TOI computer failed to materialize, mostly due to the fact that it required an 80-column character display which in turn required the MOS Technology 6564 chip. However, the chip could not be used in the TOI since it required very expensive static RAM to operate fast enough. In the meantime, freshman engineer Robert Yannes at MOS Technology (then a part of Commodore) had designed a computer in his home dubbed the MicroPET and finished a prototype with some help from Al Charpentier and Charles Winterble. With the TOI unfinished, when Jack Tramiel was confronted with the MicroPET prototype, he immediately said he wanted it to be finished and ordered it to be mass-produced following a limited demonstration at the CES.

source: wikipedia

Repairing a defective Olivetti M21

February 23rd, 2014 4 comments
Olivetti M21

Autopsy:

Olivetti S.p.A. is an Italian manufacturer of computers, tablets, smartphones, printers and other business products such as calculators and fax machines. Headquartered in Ivrea, province of Turin, the company has been part of the Telecom Italia Group since 2003.

The primacy of the first PC can be assigned to Olivetti thanks to Programma 101, which was produced in 1964 and had a big success in the U.S. market.

Olivetti’s first modern personal computer, the Olivetti M20, featuring a Zilog Z8000 CPU, was released in 1982. In 1983 Olivetti introduced the M24 and in 1984 the M21 (the first and last of transportable of Olivetti), a clone of the IBM PC using DOS and the Intel 8086 processor (at 8 MHz) instead of the Intel 8088 used by IBM (at 4.77 MHz).

The M24 was sold in North America as the AT&T 6300. Olivetti also manufactured the AT&T 6300 Plus, which could run both DOS and Unix.

The comparison (before / after):

Repairing & things before of the Cleaning:

Defects:

  • Mirror image.
  • Sometimes garbled image with using the ISA Bus.

Replaced parts:

  • Replaced a 74LS245N on the motherboard side.
  • Replaced a 75LS244N on ISA expansion Module.
  • Removed the battery for the Realtime Clock.

Upgrade:

  • Bios v1.36 to v1.43 (latest).

source: wikipedia