Monday, January 21, 2019

The IBM PC 5150: Part 5 - The mystery video card

Ok, continuing from the first expansion card investigated, here is the second, the display adapter. We know the card is a Color Graphics Array (CGA) compatible card as it drives the IBM 5153 CGA monitor with the system. The card has a 9 pin D female connector and two RCA jacks.

Comparing this to the official IBM board, this is not an IBM board. Wow. The card is not an IBM monochrome display card either. It kinda looks like an EGA card from the bracket but it isn't the IBM EGA adapter.

There are few markings. The back has zero markings, the front has Made in Taiwan and C0637 near the ISA connector and Micro 007 OK in the upper left.

Looking for competitors, it isn't a Hercules Graphics card which came out in 1984 and was popular.

Note the card has a Motorola second source UM 6845R display chip, helping to verify a CGA heritage - EGA cards have more large chips.

Forum posts here, here, here, and here keep trying to identify the card and the precise (no pun intended) functions of the RCA jacks. One for color, one for B/W?

Help came from Dave Astels looking on the fabulous graphics card site
This page has the closest picture, identifying the card as a UMC UM6845R CGA.

  • Made by:UMC
  • Codename:UM6845R
  • Bus:ISA 8bit
  • Memory Size:16kB
  • Max Memory Size:16kB
  • Memory Type:DRAM
  • Card Type:
  • Outputs:9 pin D‐sub, RCA/CINCH
  • Power consumption (W):0.65
  • Core Clock (MHz):1
  • Sold by:Precise

Ok, so the manufacturer is UMC, Unicorn Microelectronics Corp, Santa Clara, CA USA, later sold to UMC United Microelectronics Corp., Taiwan. See this book for some info on the acquisition. It seems this pair of companies have had issues, from chip manufacturing to counterfeit Nintendo video games.

According to a UMC data book (who remembers these?!?!) from 1990, page 3-68, UMC made the UM6845R CRT controller, the one on the board.

The cards were sold by Precise according to two sources. I did get a hit for Precise on this South African sales site, listing it as a Precise 445 and saying it is CGA and MDA compatible (like a Hercules) which would be amazing but I seriously doubt this. Further searching for a Precise or 445 graphics card turned up zero.

I found CGA card compatibility tester software on the Oldskool PC web site that might be handy later

The output RCA connectors are marked J4 and J5. With no other connectors/jumpers, the 9 pin D female CGA out must be J1.

J2 may be a composite video breakout and J3 a light pen interface per the official IBM CGA card per this page. As I'm not interested to get that far in the weeds, I'll leave that for another time or person.

Ok, anyone have some manufacturing or sales info? I'd really like to know if this card was put in by the reseller who was an IBM dealer (likely) or maybe replaced later. And why this card? Cost?

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