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Conference hydra::amiga_v1

Title:AMIGA NOTES
Notice:Join us in the *NEW* conference - HYDRA::AMIGA_V2
Moderator:HYDRA::MOORE
Created:Sat Apr 26 1986
Last Modified:Wed Feb 05 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:5378
Total number of notes:38326

3621.0. "Impulse-030 problem" by SALEM::LEIMBERGER () Tue Mar 27 1990 10:41

    Looking thru the "Impulse Gazette" I came across an article that
    addressed a problem where Turbo silver would not run on a 030 
    2500. The aricle stated that somethig was writeing data into 
    location zero,other than what silver wanted to see(a series of 4
    zeros).In digging into the problem it was found that Turbo Silver
    was not the problem.Other software was experiancing the same 
    trouble.The culpert turns out to be the 2091 disk controller,
    not the 030 card.Impulse says they have a patch that will fix
    the problem,and can also be used by 500 owners having problems
    running silver with the A590.So if anyone out there has had 
    this problem the fix is avalible.Impulse request you send them 
    a blank disk.For more info
    	Impulse phone(612) 566-0221
    
    Some new products were also announced. the Firecracker/24 will 
    fit into any 100 pin buss connector on the amiga mother board.
    it supports numerous resolutions,and has it's own video ram.
    The output is RGB,NTSC,and S VHS.It comes with a paint program
    that is supposed to allow painting with 16 million colors realtime.
    price 895.00 (available july 4)
    
    MegaDrive - 600meg removable read,and write optical drive.the average
    seek time is 61Msec,transfer rate is 1.2meg bytes/sec,disk size
    5 1/4. the list price is $5000.00,and the media is $250. Impulse
    is offering the drive,cable,and software for $3995.00,and media
    for $199.00. available now. 
    
    while pricy these new products are what the amiga needs to maintain
    it's edge in the video market. This week Computer Cronicles (PBS)
    had a short bit on Commodore,s new authoring system.(very nice)
    This was followed by products for the other platforms out there.
    The product for the I** was a hardware card costing $2400.00. The
    manufacturer of this product stated that while the the amiga was 
    the best presently it is loosing ground because of it's inability to 
    display enough colors,and they decided to go with the I** platform 
    because it is a wonderfull market.Some people just cannot stand
    the temptation to shoot themselves in the foot.(guess they could
    not understand the value a $2400 add on would give the Amiga).
    Well with the new products on the rise it is going to be an interesting
    year.
    							bill
    ps. I took the wife shopping,and while she was looking thru the
    craft store I walked over to a clone dealer's.They had several games
    on display.I can never fail to be amazed that people really buy
    that stuff
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3621.1surprized meSALEM::LEIMBERGERTue Mar 27 1990 10:534
    Oh! forgot to mention that contray to what I always felt,the
    broadcasters tongue did not fall off when he sad the A___a word.
    
    							bill
3621.2BOMBE::MOOREEat or be eatenTue Mar 27 1990 17:4910
    The 'location zero bug' has been the topic of much discussion.  As I
    understand it, some programs (incorrectly) assumed that location zero
    would always contain a value of zero.  It always had in the past.
    Commodore decided it was time to end this sloppy coding practice, so
    they purposefully stuffed a non-zero value there in the 1.3.2 update.

    While patching location zero to contain the value zero 'fixes' the
    problem without breaking anything else, it's really only masking the
    fact that the *program* employs improper code.  They've treated the
    symptom rather than the disease.
3621.3BAGELS::BRANNONDave BrannonWed Mar 28 1990 00:1413
    re:.2
    
    According to the story on Usenet, what happened was CBM's debug version
    got shipped by mistake.  It poisons location zero as a way of trapping
    coding problems like bad pointers that would otherwise just lurk as
    a subtle bug.  Like the one referred to in .0.  I can't think of any
    good reason why a program should expect or need location zero to
    contain a specific value.
    
    It's kind of sad that they blame CBM for the problem.  It's a bug they
    should fix.
    
    -Dave
3621.4why zero???SALEM::LEIMBERGERWed Mar 28 1990 08:1715
    re .2 I can see your point? But If the software(application program)
    is at fault then you would expect the problem to occure all the
    time. turbo Silver runs on the other vendors 030 products with no
    problem.Th earticle I read also stated that CBM had said that the
    problem was fixed,and should not occure in the future.I don't
    understand enough about programming to access this type of problem,
    but I thought I would post it just in case someone was suffering
    from it.But now that we are in the discussion what is the primary
    use of location zero. If it is not reserved for the operating system,
    and could be used by applications how should it initilize? Also is
    it good design to have hardware that writes to location zero for
    no apparent reason? Remember I don't have a good grasp of his location
    zero stuff but am very interested in what should be happening to
    it.
    								bill
3621.5CLO::COBURNGrowing older, but not up...Wed Mar 28 1990 16:3124
    One of the most common programming errors is to use an uninitialized
    pointer to access some data. Usually uninitialized pointers have a
    value of 0 - hence they are pointing to location zero. 
    
    That is one reason why the VAX is setup to not allow access to page 0 -
    all these errors are trapped via the Memory Management Hardware.
    
    The way to avoid using a NULL pointer (C speak) is to test the value to
    see if it is NULL (usually = 0). This can be miss coded to look where
    the pointer is pointing and test that for a zero. If not zero use the
    value as a new pointer for the next operation. This is where
    applications are broken. They should be fixed.
    
    Any application that randomly changes memory is broken and on a system
    without MMU protection will cause other applications problems. 
    
    I don't know what the problem with the CBM's 030 product was (it
    contains a MMU - could it be protecting some portion of memory?).
    
    Usually the 680x0 systems use the locations at 0000 as the interrupt
    vectors - although these can be moved on the 020 and 030, not sure
    about the 000 and 010 cpus.
    
    John
3621.6BOMBE::MOOREEat or be eatenWed Mar 28 1990 19:534
    re: .4
    
    The hardware was *not* writing to location zero, the new version of
    software shipped with that hardware was.