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From: labc-2aa@web-4h.berkeley.edu (Greg Burrell)
Newsgroups: comp.sys.cbm
Subject: Re: Sick C64
Message-ID: <1989Oct5.032118.26864@agate.berkeley.edu>
Date: 5 Oct 89 03:21:18 GMT
References: <936@amc-gw.UUCP>
Sender: usenet@agate.berkeley.edu (USENET Administrator;;;;ZU44)
Reply-To: labc-2aa@web-4h (Greg Burrell)
Organization: University of California, Berkeley
Lines: 85

In article <936@amc-gw.UUCP> marty@amc-gw.UUCP (Marty Akerman) writes:
>I have a C64 that I recently purchased second-hand.  
>The problems:
>  1:  It seems to have trouble running canned (purchased) programs from
>      disk.  ... Programs I have written and stored to disk load and run 
>      fine, but they are all (so far) in basic, and much smaller than the 
>      canned programs.

	Ah, the infamous head-alignment problem. Simply put: the read/write
	head of your disk drive is out of alignment. The canned programs
	were written by a drive that has correct head alignment and since
	your alignment is bad, your drive cannot position itself in the 
	proper place to correctly read all the data. Why does this happen?
	Largly because copy-protection schemes cause the head to bang
	repeatedly against the head stop. (That chattering noise you often
	hear when loading commercial programs.) Eventually the head goes out
	of alignment like yours. This is both the fault of software publishers
	who use copy protection and bad design by Commodore.
	Programs you write and save now will be
	written to the disk with incorrect alignment. Unfortunately, if	
	you get the alignment fixed you will most likely not be able to 
	read programs you saved under the bad alignment. How do you get 
	the alignment fixed? Several ways:
	1. There  are programs available that will tell you how far out
  	   of alignment your read/write head is and will include 
	   instructions on how to adjust it yourself.
	   Drawbacks: Your drive has to be well enough to load the 
		diagnostic program or you have to be able to borrow  a
		good drive. Also, some disassembly of the drive is
		required.
	2. You can look for a repair center that will do this. This might
	   cost. Personally I think option 1 is better because it is
	   very likely that your alignment will go out again sometime
	   in the future. Also, you become more familiar with the drive
	   and how it works.


>  2:  Picture quality is generally lousy.  The antenna cable (C64 to TV)
>      is VERY sensitive to orientation, coiling, what it's near, me touching
>      it, cats, weather, what I had for lunch, etc.  Generally what I see is
>      sinusoidal waves across the picture, sometimes the screen is covered
>      with snow.  It can get so bad that I can't even read those big basic
>      characters.
	Sounds like your cable is not shielded and is picking up stray 
	interference. Try finding a replacement.


> Other Questions:
>  1:  I've read and heard about the "fast load cartridge".  I gather this
>      is a cartridge that plugs into the cartridge port on the back and
>      speeds up disk accesses enormously.  Sounds like a terrific idea.
>      Where can I get one?  How does it work?
	There are a lot of fast-load cartridges available. A pretty standard
	one is called Fast Load and is put out by Epyx. They do not speed
	up all disk accesses, but do cause most programs to load 3-4 times
	faster. If there is a software store in town you might try there.
	If you have Wherehouse records, they sell a lot of software and
	should have one. Otherwise, pick up a C64 magazine like 
	Compute's Gazette or Commodore and mail order a fast loader.
	Basically, they bypass a lot of the error checking done by the
	drive, use faster routines to read data from the disk, and
	improve communication between the drive and computer.

>  2:  I would be interested in doing some assembly language programming.
>      Are there assemblers available or do I have to hand assemble (yuk)?
>      Where can I get one?
	Abacus software puts out a decent assembler. Commodore also offers
	one. Look at a software store, or mail-order catalog. There are 
	several available, but I think the one from Abacus is pretty 
	standard.

>  3:  Any other words of wisdom you could offer a novice C64 hack?
	Just have fun. There are a lot of books and mags out there that
	have lots of info. Particularly good is a magazine called 
	Transactor. Its very technically and hacker oriented. Most 
	importantly, post to this group with your questions. There are
	a lot of knowledgable people out there just waiting to answer.


			-Greg


Greg Burrell
labc-2aa@WEB.berkeley.edu
University of California, Berkeley