I love my 64c but...

Disk drives, Monitors, SuperCPU etc.
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eslapion
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I love my 64c but...

Post by eslapion »

A few months ago, I traded 25 of the M27C512-90B6 PROMs I had left in stock to Ray Carlsen for a C64c board 250469 type NTSC.

I changed the ROM on it for a CMOS, changed the 74LS14 and LS08 with HCT chips.

I really like this little board as it consumes very little power compared to other C64 boards and consequently produces very little heat. No heat sink is required on any of the chips including the 8562 HMOS VIC-II.

All the tests I ran on it went well except for one; running carts with my 1541 Ultimate I+

A few years ago, Lordcrass converted the .CRT images of the Zaxxon and Super Zaxxon cartridge games in a slightly different format to make them compatible with EasyFlash 3 and it turns out this format is also compatible with the cartridge emulator of the 1541 Ultimate series updated firmware. Super Zaxxon (the cart version, not the disk version) being one of my favorites I was thrilled.

When I tried using emulated carts with the 1541 Ultimate on the 64c board, most of them failed including the Super Zaxxon cart.

1541 U I+ cartridge emulation works perfectly well on my board 250466.

A few years back, I converted my 250466 to use a 8500 CPU and 8562 VIC-II to make it leaner. The change of these 2 chips to HMOS technology didn't cause any problems.

Back in 2011 I posted:
Yet again, my good old "uncle" 250466 based 64 went berzerk on me because its 6567R9 NMOS VIC-II overheated.

Over the last few years, I made sure I had a good heat sink on this chip but it seems it wasn't enough.

I was told the HMOS based 8564 used in the 64c produces almost no heat but never bothered to verify. I didn't even know if the pinout was compatible. Turns out the only difference is with pin 13 (Vdd) where the old 6567 receives 12V and the newer HMOS wants 5V. A direct swap would probably bust the new chip.

All I did was bend outward pin 13 of the new chip, solder a 0.1uF cap. between pin 13 and pin 20 to filter the voltage and attach pin 13 to pin 40 where the 5V comes in.

Well, the legend is true, the HMOS 8564 produces virtually no heat compared to the original VIC-II and has a better quality video signal.

No more lockups, crashes and screenfuls of garbage.
r.cade noted I have in fact used a 8562 - the 8564 is a 48 pin version of the VIC-II specifically designed for the C128.

Note to Groepaz, the soldered 906114-01 was replaced by a good 'ole M27C512-90B6 and no bus contention ever occurred; tested with a 500MHz logic analyzer...

At this point I have strictly no idea why 1541 U cart emulation will work ok on the 250466 and crash on the 250469.


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Gyro Gearloose
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Re: I love my 64c but...

Post by Gyro Gearloose »

I think I might replace the VIC-II in my breadbin, those old chips do run very hot. But I didn't find the prices on eBay very appealing. Appalling, yes. Do you sell 8562s?
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Re: I love my 64c but...

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Gyro Gearloose wrote:I think I might replace the VIC-II in my breadbin, those old chips do run very hot. But I didn't find the prices on eBay very appealing. Appalling, yes. Do you sell 8562s?
I sold all those I got afford to rid myself of but I am quite sure you could find a few on Amibay for a reasonable price.

If I stumble across more in the ton of junk Jean-Claude Lachapelle gave me then I'll let you know.
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Re: I love my 64c but...

Post by eslapion »

What VIC-II do you have for your machine? The 6567R9 still uses 12V but it's not as bad being a later generation.

I checked on "feepay" for a Commodore 8562 and found a few at about 15$US - seems a reasonable price.
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Re: I love my 64c but...

Post by Gyro Gearloose »

It's a R56A, can you believe it? 250407 mobo. I don't even know when and where I got this particular 64, it's not the one I made from the 4064 and a VIC-20 case back then. I have two more R56As and a R8 as well in *my* "ton of junk". I also have a 64C so I imagine there's already a 8562 in there?

Well, 15$ US plus shipping, still seems expensive but I guess we're at that part of the curve where 64s aint' cheap anymore.

Meh, I still need to pluck that SX-64 from the back, I wonder what VIC is in there?
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Re: I love my 64c but...

Post by eslapion »

@Gyro
The VIC-II you have is truly the "small scale heating system" version which also happens to generate a lot of vertical noise.

If you want a really good deal on Commodore components then I suggest you get in touch with Ray Carlsen.

The 64 you made from a 4064 board fetched at Addison, you traded to me back in the late 80s as I clearly remember it ended at "La Maison du Logiciel" in exchange for some Amiga stuff. I had put it in a normal C64 case at that point.

I still have the 250425 you traded me for the SX-64 around 1998. It was fitted with an R9.
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Re: I love my 64c but...

Post by eslapion »

Nobody seems to know why the 1541 U I+ cartridge emulation would work fine on a breadbin but not on a 64c... oh well, another unresolved mystery of the sixtyfour...
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Re: I love my 64c but...

Post by Gyro Gearloose »

Yes, but do you adore your sixtyfour?
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Re: I love my 64c but...

Post by eslapion »

Gyro Gearloose wrote:Yes, but do you adore your sixtyfour?
Depends on the days... sometimes I adore my sixtyfour ... sometimes I abhor my sixtyfour ...

Anyways, concerning the cart emulation problem and compatibility with the 64c, I suspect the large PLA of the 64c uses faster technology and this causes problems with the ROMH - ROML lines. Possibly delaying these lines will do the trick...
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Re: I love my 64c but...

Post by Gyro Gearloose »

You can prop a door with it, scoop a litter box with it, I adore my sixtyfour!
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