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1985 PCs Limited Turbo PC

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  1985 PCs Limited Turbo PC by Bill Degnan - 06/24/2023 17:25
The 1985 PC’S LIMITED Turbo PC. Click image for larger view.


ARC produced the first Turbo PC motherboard. Click image for larger view.


Newest chip dates are 25th week of 1985, making this an early model. Click image for larger view.


This machine was donated to Kennett Classic as unoperational. I replaced the power supply with an original IBM XT supply and replaced the hard drive controller card with a similar clone card. I temporarily replaced the bad Mitsubishi disk drive so I could access the hard drive to revert the OS from IBM DOS 3.3 to MS DOS 3.1. Someone had attempted a disk doubler, but failed to get it working correctly. A THESYS RAM / serial card was installed, but I am unsure if this card was added later or came originally with the system. The diskette drive controller card is branded "PC'S LIMITED"

There is no known operations / hardware guide for this motherboard, but similar board's documentation is enough to assist with diagnosis of problems.

More Photos

NEXT: System often boots up to an error message:

ARC Turbo Board
X Turbo System Error # 04

Sometimes the system boots without error, and additional system info is displayed to indicate turbo mode is active. One simply hits enter to bypass the message. System reports a full 640K RAM. I believe the Turbo mode is not active when the error appears, which I assume means the system operates at only 4.77 Mhz. So the next thing is to fix the Turbo issue.

Also - The display when first powered on displays in red, it will need service.

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