It won't play Crysis.

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tricky
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Re: It won't play Crysis.

Post by tricky » Sun Oct 08, 2017 7:05 am

Nice, I'd like to do something a little more exotic than two 74ls00s, but it's the analogue side that scares me.

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hoglet
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Re: It won't play Crysis.

Post by hoglet » Sun Oct 08, 2017 7:17 am

Are you using a 65C02?

The reason I ask is that I understood the NMOS 6502 could not be clocked at less than 100KHz, because internally it dynamic logic for many of the registers (which rely on charge storage for correct operation).

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JudgeBeeb
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Re: It won't play Crysis.

Post by JudgeBeeb » Sun Oct 08, 2017 8:19 am

hoglet wrote:Are you using a 65C02?

The reason I ask is that I understood the NMOS 6502 could not be clocked at less than 100KHz, because internally it dynamic logic for many of the registers (which rely on charge storage for correct operation).
Nope. It's a Rockwell R6502AP to be precise (but I assume all the NMOS variants are basically the same in this regard). However, since all it is doing is executing an endless series of NOPs, the only register in play is the PC. So maybe that is why it seems OK.
I have a 1MHz crystal on order which I will be using for the clock going forward as I start to try to do something more serious.
tricky wrote:Nice, I'd like to do something a little more exotic than two 74ls00s, but it's the analogue side that scares me.
Same for me. But there is nothing analogue going on here.

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JudgeBeeb
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Re: It won't play Crysis.

Post by JudgeBeeb » Sun Oct 08, 2017 12:58 pm

Now running at 122kHz.

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JudgeBeeb
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Re: It won't play Crysis.

Post by JudgeBeeb » Sun Oct 08, 2017 6:50 pm

I have now added an EPROM to the circuit with a very simple program (just a loop that increments X and stores in a non-existent RAM location). I have no I/O, but I could see it running on my knock-off Chinese USB logic analyser.

cmorley
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Re: It won't play Crysis.

Post by cmorley » Sun Oct 08, 2017 7:10 pm

Good stuff. Some 7 seg displays and a numpad next?

I do love how easy it is to get a 6502 executing code and working with EPROM & RAM even on breadboards.

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JudgeBeeb
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Re: It won't play Crysis.

Post by JudgeBeeb » Sun Oct 08, 2017 7:22 pm

My initial enthusiasm may not have been warranted. It is not working as expected.

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