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AST RESEARCH, INC.         TECHNICAL BULLETIN # 1200A                2-8-96

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	       Premmia GX Poor PCICLK Signal Quality On Riser Card


PROBLEM

The Premmia GX system may hang when executing code which involves IDE 
disk access.  Hard disk file corruption may occur in conjunction with the 
system hanging.  The failure occurs when the IDE hard drive is using the 
CMD PCI0640B IDE controller located on the system riser card 
(part number 202717-001).

The failure occurs within the following configuration:

1. The system is a Premmia GX P90 or P100. 
2. A PCI add-in card is in the lower slot (J1).
3. The CMD IDE performance enhancement feature referred to as "32-bit 
   disk access" has been enabled.  It is enabled using the AST utility 
   SETIDE.EXE.

The failure will never occur when the lower slot is empty.


CAUSE

Installation of a PCI add-in card in the lower slot causes a marked ringing on 
the PCI clock to the CMD PCI0640B IDE controller on the riser card.  
This causes an illegal clock transition at the controller which leads to 
double-clocking within the controller.  The clock signal is fine when the slot
is empty.


SYSTEMS AFFECTED
AST PART NUMBER AND DESCRIPTION

501457-XXX      PREMMIA GX P/90
501700-XXX      PREMMIA GX P/90
501522-XXX      PREMMIA GX P/100


SOLUTION

A newer version of the riser card (P/N 202717-002) for the Premmia GX 
includes a PCI clock routing modification, which does not exhibit the 
symptoms discussed under CAUSE above.  The new riser card can be 
substituted for the 202717-001 riser card in Premmia GX systems, but there 
are functional differences between the two riser cards.

This riser card uses the CMD PCI0646 controller, which will enable 
the system to support up to two PIO mode 4 hard drives.  The PCI0640B on 
the 202717-001 supports up to two PIO mode 3 drives. 


CAUTION

This modification should be performed only by a qualified service technician.  
It is strongly recommended that this change be completed by an AST 
Authorized Service Center.  In no case will AST Research, Inc. be liable for 
damage to the system and its components, or loss of data caused by improper 
modification.


PREREQUISITES

A full backup of all data on the hard drive in the computer is strongly 
suggested.


TIME REQUIRED

30 minutes.


STATUS VERIFICATION

The revision level of the AST riser card can be identified by observing the 
revision letter at the end of the nine-digit part number located on the solder 
side of the card.


TOOLS REQUIRED

Standard computer tools.


INSTALLATION PROCEDURE

Refer to the system Hardware Maintenance Manual (P/N 002143-001A).

Removal and replacement of system "Field Replaceable Units" (FRUs) 
should only be performed according to the installation procedures approved 
and prescribed by AST Research, Inc.  

Remove the riser card according to procedures approved and prescribed by 
AST Research, Inc.


CHECK-OUT PROCEDURE

To verify proper operation of the system upon completion of this change, 
follow the Set-up and test procedures described in the AST User's Manual.

NOTE

Warranty reimbursement for this change requires prior AST Research, Inc. 
approval. 

The warranty on this system will become VOID if this change is completed 
by ANYONE other than an AST Authorized Service Center.