Assistance with a sixty-clone 250466

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Nwfodder
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Assistance with a sixty-clone 250466

Post by Nwfodder »

I'm working on building a sixty clone (rev. 250466) and I have it up to the point where I have no video signal.

My question is that if I am using the TOLB for an 8701 replacement will I need a separate crystal in Y1, or does the TOLB have a clock crystal incorporated into it?

Thanks


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eslapion
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Re: Assistance with a sixty-clone 250466

Post by eslapion »

The active oscillator onboard TOLB performs the function of the crystal so there is no need for a crystal when you use TOLB. There is also no need to adjust or even install the variable capacitor CTI connected to the crystal on a C64 board.

PLAnkton replaces the PLA and Saruman 64 replaces the 2 DRAM ICs.

Make sure ALL logic ICs on your 250466 are either 74LS family or 74HCT. Avoid at all costs 74AHC, 74HC, 74AHCT, 74AC,74ACT because they are either too fast or have the wrong threshold logic level.
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banman
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Re: Assistance with a sixty-clone 250466

Post by banman »

Hi eslapion,


eslapion wrote: Mon Jul 05, 2021 8:43 pm Make sure ALL logic ICs on your 250466 are either 74LS family or 74HCT. Avoid at all costs 74AHC, 74HC, 74AHCT, 74AC,74ACT because they are either too fast or have the wrong threshold logic level.
Very interesting. This should be a complete topic on it's own. This has prompted me to do some further investigation.
What is 74F series of chip, would this be suitable?
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eslapion
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Re: Assistance with a sixty-clone 250466

Post by eslapion »

banman wrote: Fri Jul 09, 2021 10:49 pm... This should be a complete topic on it's own. ...
Well, it's the same old story about the families of logic chips and their properties as well as their evolution.
What is 74F series of chip, would this be suitable?
In ancient times, there were TTL logic ICs and they all consumed lots of power. The faster they were, the more power they consumed and the worst of them all was the 74F series. You can find them in a few Amiga computers and the fastest PCs of the 1980s. Since they are of the TTL family, they are powered at 5V and their logic threshold is 1.5V, just like the 74LS found in VIC-20s and C64s.

Today, to get the same Vcc, speed and logic threshold, you would use a 74AHCT logic chip which consumes 95% less power. 74F logic ICs are a thing of the past but back then they were necessary to get decent speeds but they are now considered obsolete power hogs.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
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eslapion
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Re: Assistance with a sixty-clone 250466

Post by eslapion »

Why you should always make sure you use the correct type of chip when building a Sixty-Clone:



Technical information:

https://www.onsemi.com/pub/Collateral/AN-368.pdf
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
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Re: Assistance with a sixty-clone 250466

Post by Nwfodder »

Thanks. I'm watching this right now. Very interesting info on here. I won't get time to fully troubleshoot this just yet on my board, but when I do, I'll let this thread know. Thanks everyone for the info!
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