[SunRescue] TOD Failure: No, We're Not Crazy

rescue at sunhelp.org rescue at sunhelp.org
Thu May 3 06:51:48 CDT 2001

The dialog on the NVRAM replacements with different people reporting
receiving the dreaded

FAILURE: TOD (f20007fa) Bit Failure, Exp =3D 000000ff, Obs =3D 0000007f

message and the machine not autobooting has been bugging me big time.
I've been refurbing Sun boxes for years and can go back to past year
invoices showing that the very same part number chip I used last year =

and the year before, flat out don't work now.

I contacted ST Microelectronics, the manufacturer of the chip that Mouser=

Electronics provides and they advised me that ther WAS a die change in th=
M48T02 and M48T12 chips in June of 2000.  That change makes it impossible=
set the MSB of the 0x7FA address to a 1.

A part of the last meddage I received follows:

"... The M48T02 has been in production for 10+ years and undergone at lea=
two die revisions or "shrinks".  In May of 1998, the first shrink (that I=
of) occurred and overall functionality was basically unchanged (at least =
regards to the bit in question).  This shrink also resulted in 100%
distribution to 70ns.  In June of 2000, a second shrink occurred which le=
d to
the change in functionality... [icluding] a more literal [adherence to] t=
data sheet which states, "the
bits marked as '0' in Table 10 must must be written to '0' to allow for
normal TIMEKEEPER and RAM operation." (see section under 'Setting the Clo=
on page 9 of the attached data sheet), was also applied.  Therefore this
latest revision will not allow the bits defined as '0' in the Register Ma=
p to
be written to any other value.  This may explain the problem you are
experiencing.  Devices with a date code of approximately 0025 or later wi=
ll be
the latest revision and have this limitation. "

So, chips manufactured before June 2000 should work.  I still have reques=
into Sun and Mouser.  More news when I find out more...

___________________________________________________________________ =

---- Harry J. Regan
---- Phone: 202.310.2719
---- FAX:   212.202.3923
---- harry.regan at usa.net =

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