Re: kablooey

On Fri, 10 Mar 2006 10:21:13 GMT, Ross Herbert
<rherber1@xxxxxxxxxxxxxx> wrote:

On Thu, 09 Mar 2006 08:15:13 -0800, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

SNIP

We got one back yesterday. Two chips are running hot, the MC68332 CPU
(directly on +5) and a big Xilinx SpartanXL FPGA. The FPGA is powered
from +3.3, linear-regulated from the +5 supply, but it connects to the
CPU bus, and it's supposed to be 5-volt tolerant on its I/Os. So it
looks like the +5 blew the CPU and it, in turn, pulled up a bunch of
the FPGAs i/o pins and fried it too.

What's cool is that the CPU is running very hot but is still executing
the firmware! And the FPGA is hot and really dead.

We're going to replace both chips (418 pins total!) and see how things
look. There are 5 more FPGAs on the board, but we're optimistic
they're OK.

Here's a pic of the board.

http://www.highlandtechnology.com/DSS/V375DS.html

John



Hi John, what is the customer going to do to prevent a repeat?


Dunno. He's harassing the crate vendor now. They're British, and what
with time zones and the classic British time constants, it may take a
while to resolve.

Perhaps you can sell him a VME cage/backplane and PSU which you know
is ok. That way he can definitely guarantee warranty repairs if a
similar failure occurs within the warranty period, plus, you get an
extra sale....

I don't want to be in the iron business; the margins are pitiful. And
I don't want to sell anything that would break your toe if you dropped
it.

I might sell him a high-power clipper he could hang on the 5-volt buss
in the crate, to gobble up the overshoots.

That's how Motorola used to do it back in the 70's - 90's. Customers
were prepared to use their overpriced racks and PSU's just in case the
boards failed due to an occurrence such as your customer encountered
with the rack/PSU they sourced themselves. Possibly they were trying
to reduce costs and chose cheapness over quality.

Yeah, I'll have to try to get the history of the crate buy.

Anyway, I thought people ought to be reminded of how some power
supplies can be "teased" to produce outrageous outputs.

John

.

Relevant Pages

  • Re: kablooey
    ... waveform generators failed, in the same VME crate, simultaneously. ... Two chips are running hot, ... and a big Xilinx SpartanXL FPGA. ... CPU bus, and it's supposed to be 5-volt tolerant on its I/Os. ...
    (sci.electronics.design)
  • Re: kablooey
    ... That's above the 5.5 abs max for my CPU and FPGA chips, ... So I asked them to switch power off for various times, ... VME crates are from the days of LS TTL, and those chips would generally ... the MC68332 CPU ...
    (sci.electronics.design)
  • Re: kablooey
    ... John Larkin wrote: ... Two chips are running hot, ... and a big Xilinx SpartanXL FPGA. ... CPU bus, and it's supposed to be 5-volt tolerant on its I/Os. ...
    (sci.electronics.design)
  • Re: Is 50 MHz doable for a complete newbie?
    ... >a CPU, FPGA, some SDRAM... ... ground plane and a single or split power layer. ... close to the CPU or FPGA driving the ... port pins and FPGA pins to test points. ...
    (sci.electronics.basics)
  • Re: Applying Intel IA32 Microcode Update [OK]
    ... You mean the volatile storage? ... Inside the CPU, I presume. ... One mode is to have a separate serial EEPROM that the device loads from, ... just not necessarily in the FPGA ...
    (comp.os.linux.misc)