Anyone have a guess as to why my DTK '386-25 (Pheonix bios) likes to
freeze up for 15-60 seconds at a time every once in a while?
        It's been doing this for a year now, since I got it, and it seems to
be tied into the video...
        Much more likely to freeze if it's trying to put up a 256-color screen.
        But freezes at other times, too.
        The video card is a Hyundai, but acts like an ATI wonder.

16 responses total.

        You might try removing the video card and replacing it with another
kind.  The problem might be with your video card.
        You could also put the video card in an 8 bit slot to see if that
makes a difference.
        How often do you get this problem?

   John's idea is sound: try and isolate the problem.

Putting the video card in an 8-bit slot would NOT be good for the 
video card.
The problem occurs every once in a while, much like line noise.
sometimes several times in an evening, other times not for a couple of
days or more.
I do not have another video card, except an old CGA, and don't really want
to leave that in for days.

        You said it freezes for a minute, give or take a minute.  Is
everything normal after things start working again?
        You might also try a log of short notes about conditions when it
freezes... if it always happens after a certain program, or certain
programs (example: video programs, using your term program, just after
logging on, only after using your computer for several hours, etc) it
could help to figure out what's going on.
        Isolating a problem can take a lot of patience and effort, especially
if it's intermittent like this one.

Everything is fine after it's done freezing. It freezes most often when
loading a 256-color screen in games like Wing Commander. 
As soon as it thaws, the disk heads do a full-length "seek" and it 
continues where it left off.
This is no big problem, which is why I've never gone crazy trying to figure
out what the deal is. It's just annoying.

Is the disk light on while the system is frozen?

Most 16-bit VGA cards have autodetect circuitry in them that automatically
shifts the card into 8-bit mode if it discovers that it's plugged into
an 8-bit slot.  Others have to have a DIP switch or jumper set.

Nope, the disk light is off.
I haven't looked at the video card in a year, so I may be forgetting, but...
How would it fit in an 8-bit slot? I seem to recall the 8-bit slot
being a mite too short...like by half...

        If it usually happens with 256 color graphics, it's probably a
problem with the memory chips on the card.  Further, it's probably a
problem with the extra memory (VGA cards have 256K, SVGA cards have 512K,
1024x768x256 color cards have 1024K)), which is likely to be replaceable.
If it's DRAM memory (two rows of pins, looking like what most people would
call a "memory chip"), it won't even cost much, as DRAMs are selling for
$40 or so mail order or used.  If it's VRAM (1 row of pins, looking like a
terminating resistor on a hard drive) it'll cost somewhat more than that.
        If you can replace all the memory at once, it'll be much quicker to
determine if this is the problem.  If you can even get one chip, though,
and replace one chip at a time until you find one that's defective, you
may be able to fix the problem.
        You might also try pulling all the memory off the card and then
re-insert it.  It might be just a loose chip.   If it usually fails only
after the computer has been on for a couple of hours or so (after it's
warm, that is), it's a good indication a memory chip is loose.

        The extra part of the card that fits in the extra length of an
expansion slot would just be loose, unconnected to anything.  VGA cards
often work in 8 bit cards, but are just faster in a 16 bit slot.  (Very
few other 16 bit cards will work in an 8 bit slot, but VGA cards are
often designed to work in an XT as well as an AT or 386 computer.)

It is indeed DRAM; I suppose I may have left a chip loose when I 
installed the extra 256K...
Maybe I'll yank 'em and put 'em back in.
,

The full length seek is probably a disk restore/retry.  Could still be
due to a memory or video problem -- it may have caused a disk I/O to
fail.

Definitely reseating the memory is a sensible solution.

Uh, DRAM and VRAM can both come in sips, dips, or simms.  Jep's rule of
thumb may happen to be more or less true for him, but don't rely on it
in the long run.  The difference between VRAM and DRAM is inside the
chip where you can't see -- VRAM is just DRAM with some extra logic on
the chip to get special fast video access -- basically it relies on some
architectural pecularities of DRAM.

You see, in a normal DRAM chip, a memory access actually takes place in
2 steps -- you strobe in a row address, and this causes an entire row to
be fetched out of the memory array in the chip, into a special row
buffer, and then you strobe in a column address to select one bit that
you want to read or write in the row.  When you're through, the entire
row is then written back into the memory array -- you have to do that
because the readout process is destructive -- what's in that row of the
memory array goes away when read.  Even if you don't read it, what's in
memory still goes away in less than a second, so you have to execute
refresh cycles on all of the rows of the memory array to charge it back
up again.  A refresh cycle consists of just strobing in the row address
and then not doing any column strobbing -- a "null" cycle, you might
say.  But any read or write cycle will refresh the entire row, so if you
can arrange for periodic sequential memory cycles, you're set.
Conveniently, this is just what video is good for -- and that's why the
apple ][ came out with 4K of memory when S-100 technology of the time
was hard pressed to provide 1K of relatively trouble free static RAM.  6
years later, the designer of the Sun-1 CPU had an even simplier solution
for dynamic ram refresh -- they just hooked up a periodic interrupt
source to the NMI pin of the 68000, and pointed the NMI service routine
to a list of 127 NOP instructions, followed by an RTS.  That generated
128 sequential memory references on a periodic basis--all that you
needed.

Now, in normal DRAM, you can only read or write one bit at a time.  This
is kind of frustrating since you actually are referencing at least 128
bits, and probably a lot more in today's memory chips.  The bottleneck
is, of course, the # of pins on the chips, and there's a lot of reasons
to keep the pin count down as much as possible.  Now, there's a number
of clever things you can do -- some modern chips, for instance, give you
access to 4 bits at once, instead of just one, but the essential problem
is that you're doing random access to the chip, and so you really can't
get away from having to tell it which row, and then which column.
However, video logic has entirely different constraints on it.  It's
highly sequential, and about the only thing that's really critical about
it is some of the timing -- when it wants its data, it wants it and it
can't be late.  This is a problem with traditional DRAM -- basically,
the faster the video is (like the larger the screen is), or the slower
the memory is, the less time is available for the processor to get at
the memory.  VRAM is a solution to this - basically, inside the chip,
where interconnects are cheap, a video shift register is added in
parallel with the row buffer that already has to be there.  Now, in
addition to doing a normal bit-wise read or write on one bit, you can do
a load of the whole shift register in the same amount of time.  The
shift register is then provided with independent clocks, so it can be
shifted out one bit at a time, and meanwhile, the memory array and row
buffer are absolutely free and available full-time for the processor.
Basically, this only adds about 3 pins to the package, and means the
chip is available to the processor about 99% of the time -- a pretty
good deal for video designers.

I wasn't using John's method to determine the RAM. It is DRAM.
100ns, 256x1 DRAM dippies. 
Or, at least, the half I installed is, and I can only assume the 
256K that came with it is, too. Well, I can assume or I can open it up 
and look... :)
It doesn't seem like the two would work together at all, though.

One more possibility:
 
I had this same problem whenever I loaded a communications program into
my laptop when it was at work.  My computer would hang for 20 or 30 seconds
and then keep going.  So I thought it was my communications card.  I pulled
it, ran an eraser over the connections, and shoved it back in.  The problem
was intermittant and would come and go, and my card passed all diagnostic
tests.
 
Eventually, I figured it out.  I was getting a slew of temporary read i/o
errors loading the software.  Sometimes it would only take 1 or 2 retries,
and would seem to operate close to normal speed.  Other times, it would
take 10 or 15 retries to be successful reading each track, and I'd think
my system crashed, then, poof, it would keep working.
 
I didn't figure it out until the first time it went 16 tries on one sector
and gave up with an I/O error.

No, it isn't a disk problem. This happens even when it isn't doing any 
disk read.
I'm wondering if extended memory or EMS is part of the problem. It does
it more when I'm using EMS, or seems to. 
Maybe when I open it up I'll move my SIMMs around too.

        I only know what I see.  I haven't seen that much VRAM, and all I've
seen was SIPP style.  Thanks for the correction, Marcus!

It's not at all unlikely tho that the SIP's are the current "packaging"
standard -- there's a lot of reasons why people might end up using the
same package, like design time, delivery schedules, and getting the
cheapest price by using "what everyone else is using".  It's just that
it can easily change all around when the next generation of chip comes
out, and there's usually at least one or two odd-ball manufacturers that
guessed wrong, or got a price for some non-standard lot that they
couldn't turn down.  With DRAM, usually, there's a "standard" pinout
that everyone uses, that lasts for 2 generations of memory chips, then
they have to go to a new pinout.  That's how, with the Apple II, you
could expand from 4K to 16K by just swapping memory chips and changing
two jumper blocks, and not by throwing out the motherboard and buying a
new one.  (Remember when they did that to upgrade the Macintosh?)  The
"every two generations" might seem mysterious until you consider that
dip's have 2 rows of pins -- so it has to have an even count of pins --
since each address pin with dram counts as 2 address bits, that means
adding one pin is 1 generation or 4 time the size, 2 pins is 16 times
the size, and you can only grow the package by 2 pins at a time.

Response not possible - You must register and login before posting.

- Backtalk version 1.3.30 - Copyright 1996-2006, Jan Wolter and Steve Weiss