7

22564B-1—February 2000

AMD-751™ System Controller Revision Guide

Preliminary Information

14

BAR0[3] Initial Setting Causes OS/2 Warp Install Error

Products Affected. All revisions

Description. BAR0[3] (Base Address Register 0 = Function 0, Device 0, Offset 10h) is initialized to 1,

which indicates that the AGP aperture is prefetchable. With all base address bits (bits 4–30) reset and

with bit 3 set to 1, OS/2 Warp 4.0 installation hangs. With AGP disabled, these bit settings are correct

for the AMD-751.

Potential Effect on System. OS/2 Warp 4.0 hangs during installation.

Suggested Workaround. Enable AGP BIOS settings during the OS/2 Warp 4.0 installation. When the BIOS

sets the Base Address bits of BAR1 for AGP mode, OS/2 Warp 4.0 loads correctly.

Resolution Status. No change to the AMD-751 is required.

15

Ref_5V Cannot Be At A Lower Voltage Than Vcc (3.3V)

Products Affected. C3

Description. Voltage on the Vcc (3.3-V supply) pins cannot exceed the voltage on the 5-V reference pin

(Ref_5V).

Potential Effect on System. The AMD-751 can go into a latch-up state, and permanent damage to the part

may result.

Suggested Workaround. Specify the system power supply whose outputs ramp up and ramp down, such that

the 3.3V outputs never supply voltage higher than the 5-V outputs. For more information, see the

AMD Athlon™ Processor Voltage Regulation Application Note, order# 22651.

In addition, providing a forward-biased diode on the motherboard from the 3.3-V supply to the 5-V

supply limits any 3.3-V excursions to the diode voltage drop. The power supply connector should never

be inserted or removed while power is applied to the motherboard.

Resolution Status. Fixed in Rev C5.