Image Map Image Map
Results 1 to 9 of 9

Thread: C64 vs 64C SID chip

  1. #1

    Default C64 vs 64C SID chip

    I grew up with a late model 90's 64C (actually a 64E). Lately I've been playing around with a breadbin C64 I acquired a good few years ago (which I think is a 1983 model). I know the SID chip is different between the two and they will have slightly different sounds to them, but even allowing for that the one in the older model doesn't seem to be quite right - it seems to sound slightly muffled and the dynamic range seems awfully limited, with lots of bass notes popping and high notes clipping.

    I fired up a 64C and that still has a full clean sound which is exactly as I remember.

    Both machines are connected up only over RF which won't help, but the older machine actually has a slightly better picture over RF so I wouldn't necessarily put it down to that.

    Not quite sure how much different the older machine is supposed to sound or where the problem might lie?

  2. #2

    Default

    Early production 64C's and 128's still used the old 6581 SID chip. I think most of the newer 8580 SID chips ended up in Europe because by the time Commodore started using them, sales of 8-bit computers in North America were declining steeply, while sales remained strong for quite a while longer in other parts of the world.

  3. #3
    Join Date
    Jan 2014
    Location
    Freedom City
    Posts
    6,145
    Blog Entries
    2

    Default

    Your bad-sounding SID is bad. This is a normal mode of failure for them. Eventually it will just go quiet.

    Check your power supply. In fact, if you're using an unmodified original Commodore power supply and it doesn't have actual air vents, I highly recommend shelving it and getting a different power supply.

  4. #4

    Default

    All I have left of my old 64c is the main board. I bought around this time in 1989. It has the newer sound chip. I showed it to a coworker, and his comment was "there isn't that much sound in the world!", I guess owing to the abundance of pins. Mine was purchased in one of the shops downstairs in Penn Station.

  5. #5
    Join Date
    Jan 2014
    Location
    Freedom City
    Posts
    6,145
    Blog Entries
    2

    Default

    I bought mine when the C64C first hit the stores. In fact I went to buy the breadbin model which they still had on the shelves (I think it was Target but may have been Kmart). Ironically the C64C was significantly cheaper than the C64. I think it was a promotional price because it was brand new. I think it was $200, and the C64 was at least $50 or $100 more. I only had $210 so I couldn't refuse. I used the remainder to buy a black and white TV at a rummage sale for a monitor (still have it). I wanted to buy a teletype from that sale but didn't have the cash or anywhere to put it.

    I have the original box, the metal RF shield, the Commodore 64 badge (which at one time was affixed to the dash of my car), the VIC-II, and all the keyboard springs which have since rusted. I might have the upper half of the case. I have no idea why I still have these things.

  6. #6

    Default

    Quote Originally Posted by cwathen View Post
    I grew up with a late model 90's 64C (actually a 64E). Lately I've been playing around with a breadbin C64 I acquired a good few years ago (which I think is a 1983 model). I know the SID chip is different between the two and they will have slightly different sounds to them, but even allowing for that the one in the older model doesn't seem to be quite right - it seems to sound slightly muffled and the dynamic range seems awfully limited, with lots of bass notes popping and high notes clipping.

    I fired up a 64C and that still has a full clean sound which is exactly as I remember.

    Both machines are connected up only over RF which won't help, but the older machine actually has a slightly better picture over RF so I wouldn't necessarily put it down to that.

    Not quite sure how much different the older machine is supposed to sound or where the problem might lie?
    The answer is very simple:
    try this basic program:
    http://ploguechipsounds.blogspot.com...benchmark.html

    and listen to the proper audio (look at the end of the page). If your SID doesn't sound like the references, then it's faulty.
    I use this test on any C64/128 I repair, just to understand if the SID is perfect or it's partly failed.

    Regards
    Frank IZ8DWF

  7. #7

    Default

    Is the later 8580 chip a pin compatible replacement for the original 6581 or do they require different motherboards? I have got another C64C with a slight fault - I think it's just a colour RAM problem as it largely works fine but the text displays in all sorts of weird flashing colours. However as the case is also very badly yellowed and I only have two power supplies so I can't run all 3 at once anyway I'm thinking of using it as a parts bin rather than repairing it.

    Can I take out the newer SID chip and put it into the breadbin? I can live without the 100% original sound, never really noticed the difference anyway unless viewing side by side comparisons on Youtube.

    Check your power supply. In fact, if you're using an unmodified original Commodore power supply and it doesn't have actual air vents, I highly recommend shelving it and getting a different power supply.
    I am still using the original bricks with the fake vents (although both are very late models from 1993 - I don't know whether that's better or worse). I'm aware of the problem where the voltage jumps up and fries the board, I keep checking the outputs with a meter and they are still right on the money. I was thinking of hunting down the little adaptors which protect against it. When these finally go is it gradual in which case I would notice with a meter that the voltage is increasing or does it just suddenly spike?

  8. #8
    Join Date
    Jan 2014
    Location
    Freedom City
    Posts
    6,145
    Blog Entries
    2

    Default

    By the time you notice a problem with your meter, it will be too late.
    Last edited by KC9UDX; June 27th, 2018 at 07:09 PM.

  9. #9

    Default

    Quote Originally Posted by cwathen View Post
    Is the later 8580 chip a pin compatible replacement for the original 6581 or do they require different motherboards? I have got another C64C with a slight fault - I think it's just a colour RAM problem as it largely works fine but the text displays in all sorts of weird flashing colours. However as the case is also very badly yellowed and I only have two power supplies so I can't run all 3 at once anyway I'm thinking of using it as a parts bin rather than repairing it.
    No, 6581 and 8580 can't be substituted one for the other. 8580 requires 9V analog supply and different external filter capacitors. 6581 requires 12V supply and of course different values of the filter capacitors.
    Putting an 8580 into a 6581 motherboard, kills the 8580. Putting a 6581 on a 8580 motherboard probably spares the SID but I doubt it would sound even remotely correctly.
    Color ram problems are easily solved, there's almost no fault that justifies turning a C64 into a parts unit (unless one really wants to).
    There're modern replacements for both 6581 and 8580 SIDs (swinsid) and they sound reasonably well.

    Frank

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •