My RC6502 Apple 1 Replica uses an Amtel AT28C256 for ROM and Hitachi HM62256BLP-7 for RAM, and works nicely. These are both pretty common parts used throughout the hobbiest community, with many non-official sources as well (although you need to be alert for used, possibly not tested, and possibly ...

So any parts recommended for a RAM or even an EEPROM?

You could put just a ROM on there, filling all 64K, but with no RAM, you can't have any subroutines or variables, and with no I/O...well, that wouldn't be a very interesting computer. :lol:

Yes I know that. :D But since I don’t have any RAM or I/O parts i might as well learn with just ROM for now.

Thank you!

What about just the ROM for now? The one i have is 64k(w27c512) with address pins A0 to A15. So is it a straight connections to the 6502 including the A15? Do i still need some decoding if im just going to use just a ROM?

Now that I have tested my 6502 and having a basic knowledge of what's going on, I want to start adding some memory. I would like start with a ROM(EEPROM) for now coz' I don't have any RAM yet. I have a Winbond W27c512 EEPROM that i would like to start with. So the address pins of the W27c512 (A0 ...

I bought mine from mouser, https://www.mouser.com/ProductDetail/We ... SplB6itg==

If the chip i have is an old NMOS, is it possible to single pulse it or slow down the oscillator to about 100khz? I think it's mentioned in the 6502 Primer: Clock Generation that it's not possible.
100kHz yes; but not single-pulsing it as in leaving it long enough in one state to poke around and ...

You can divide by 2 with a Flip Flop, so a single 74xx74 dual flip flip would give you options of 500khz and 250khz, chain 2 together and you'd have 125khz and 62.5khz too.

Or use a counter, something like a 74xx93 would give you the same 4 clock rate options as pair of 74s.

(I wonder about that ...

It looks like the jumper wire for the VCC is not intact so i pressed it down and made sure there’s 5v on that pin. Sure thing, now it’s working. :)

Now I just need to find a way to slow down the 1mhz clock so I can clearly see what’s happening. Is it possible to slow it down to maybe the minimum ...

I have tested the led to be working fine. For the 6502, it’s also tested to work just fine with a clone replica of Apple I i assembled. For the crystal i have no way of testing it though. I will definitely get an Oscilloscope in the near future. :)

I tried several nmos 6502 chips i have laying ...

So I tried it on a breadboard and connected all the necessary pins including the data bus pins to run the NOP code "ea". I' ve also connected one LED to one of the address bus. Powered it with a 5v power supply but I don't see to get any activity from the led. Anything I missed?

6502_breadboard ...

Yes. Not only will that work, it's the preferred method.

And yes, I believe that is an old NMOS chip which has a minimum frequency to run (IIRC, something like 100KHz).

A modern WDC 65C02 would be better but the NMOS version can certainly be used (assuming it works).

Ok thanks. So the output ...

I have an old Rockwell chip with label " R6502-13 " that i'd like to do the "Free Run" test. I'm guessing it's an NMOS chip?
r6502.PNG
I've read the 6502 Primer: Clock Generation but I do not have the parts yet as mentioned for the NMOS chip. What I have is this 4pin crystal . Will this work ...

I'm from the Philippines. I don't mind buying parts from eBay, mouser, digikey, etc.

Hi to all,

I've always wanted to do a simple 6502 project because I want to learn more about the inner workings of a computer and electronics in general. I just started reading the 6502 primer . But while Im doing that I want know the parts needed so I can get them immediately because from where I ...