Re: 6510FPGA Suggestions?

From: Istvan Hegedus <>
Date: Mon, 26 Aug 2013 16:24:04 +0200
Message-ID: <>
I thought I said the same as you. Maybe my English is not the best, but I 
said exactly the same that this FPGA64 CPU uses a fully synchronous design 
with clock enable (when I said it "slows" down there I meant the clock 
enable signal) and that is the best approach.
I said it is a drawback however because I want to interface this 6510 to 
external dram chips which are slow. The CPU is however still fast because it 
will do its job with the 1st clock cycle (fast clock) and then it suspends 
for the rest of the clock cycles until the 1MHz time elapses. Old dram chips 
however provide/expect the data out of the CPU's running cycle.
If you put it inside the GODIL then you need some tricks to handle properly 
the timings of a C64. Indeed my plan is to create a 8501 in GODIL to use in 


-----Original Message----- 
From: Mark McDougall
Sent: Monday, August 26, 2013 3:43 PM
Subject: Re: 6510FPGA Suggestions?

You are completely wrong. The best approach is a fully synchronous design 
with a clock enable.

Sent from my ASUS Pad

Istvan Hegedus <> wrote:

>I have been investigated these cores too and found FPG64's 6510 code the
>closest implementation. I am currently playing experiments with it and one
>drawback is that it uses fast clock (33Mhz) and slows the CPU down with the
>enable signal. This however is needed in order not to violate the clock
>domain of the whole FPGA64 design. It can be driven with slower clock speed
>too but it is not a good concept to have different clock speeds in your
>-----Original Message----- 
>Sent: Saturday, August 24, 2013 12:41 AM
>Subject: 6510FPGA Suggestions?
>Since for some time I am walking circles around the FPGA/CPLD bandwagon, I
>thought it might be time to have a closer look. I checked opencores and
>tried to decide where to spend some money (Altera, Atmel, Xilinx, ...?) 
>would be able to implement a 6502 and an I/O port together with some RAM 
>ROM modules. My n00b questions to the more experienced fellows:
>- how many kgates can be needed for something like I mentioned above?
>- what would be the best h/w platform/vendor and why?
>- what is the most complete/reliable 6502 core to use as starting point?
>- what can you suggest or warn about?
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Received on 2013-08-26 15:01:50

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