Re: Asteroids Deluxe - odd problem...(fixed)

Kevin Moore wrote:
> A tool like that would be very useful. I've run into this situation a
> few times before. You would think the Fluke long Ram test would catch
> it. But it doesn't sometimes.
>
> Kevin
>

The Fluke test does not occur at system speeds, rather it simply dumps
the code onto the bus via a PIA, then toggles the R/W and reads it back
through the same PIA...slow...won't catch RAM problems related to speed
unless you are using one of the Z80QT pods...

Hmm...I wonder if I could make CPU adapters for the Z80QT pod, and as I
understand the pod runs RAM/ROM tests at system speed it is a more
accurate test. The QT pods also can generate a Checksum instead of the
Fluke Signature for ROM checking. They are a bit rare though...

John :-#)#
>
> On Sun, Aug 29, 2010 at 9:35 PM, John Robertson <pinball@telus.net
> <mailto:pinball@telus.net>> wrote:
>
> Matt J. McCullar wrote:
>
> Well done, John! I know what it's like to fix a "tough dog."
> Just last
> week I had a _Ms. Pac_ motherboard that turned out to have a
> bad 2114 RAM --
> it kept cycling through the initial boot-up sequence. I had
> an external RAM
> tester that said it was okay (of course), but I've seen this
> sneaky type of
> thing happen before. Substitution nailed it.
>
> You're right about mixing up different manufacturers of RAM chips!
> Guaranteed to cause all manner of weird things to happen.
>
> Matt J. McCullar
> Fort Worth, TX
>
>
>
> This sort of thing - RAM that passes tests by test fixtures, but
> fails in the 'real' world - is a pain.
>
> I'm thinking of something that plugs into the CPU socket and after
> you 'tell' it where the RAM is located allows you to dial up the
> speed you want to test it at - or use the system clock. A simple
> Pass/Fail would suffice, you figure out which RAM is defective by
> the allocated space and if you are testing upper or lower bits (0
> - 3, 4 - 7). This could be used with any static RAM...
>
> First though I'm going to dig out my old Atari RAM/ROM tester
> (comparator) and see if it can be used this way - why design
> something new when I may have a tool on hand that can be easily
> modified to do the job I want? Now to track down my manual -
> TM-120 is the one for the Atari Automatic ROM/RAM
> Tester...probably in the filing cabinets, and I see no scans
> posted at the usual suspects.
>
> John :-#)#
>
> (Vancouver, BC, eh?)
>
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-- 
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Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
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