Recently I've ordered few R65C02P4 chips from Chinese seller on eBay.
Package arrive few weeks later. In the meantime I modified one of my 6502 boards, I've been using with classic NMOS version, by speeding generator up to 4 MHz and adding DS1232 watchdog chip. I've tested one of the received chips, but it appears not to be genuine CMOS chip, but rather NMOS version with original label sanded off and new one engraved with laser.
Board works, even works faster (due to 4 MHz clock) but it still draws similar amount of power as NMOS version (around 150 mA).

It is crucial for me to use genuine 4MHz supporting CMOS version of 6502 in my project. Why can I buy one?
Are there some trusted and tested sellers on eBay?

Is there way to test and recognize relabeled chips? They appear to be 6502s, so I can still utilize them. But I do not want to destroy them by overclocking.

It's been a few years but I did buy qty 10 Rockwell chips from Utsource.net. I haven't tested all of them, but they are 65C02 parts... low current draw and execute CMOS instructions. Apparently they still have some:

https://www.utsource.net/itm/p/199445.html

They do look a bit different from my original R65C02 parts I bought back in the 80's... markings that is.

_________________
Regards, KM
https://github.com/floobydust

You could test the undefined opcodes. Depending on how it behaves with the WDC, Rockwell, and NMOS undefined instructions, that could tell you what it is.

If it's possible to measure the current draw on its own, that might give you some information. According to the R65C02 datasheets in the archive here, that device is supposed to draw 2.6 to 4 mA/MHz. If it's going at 4 MHZ, then it should draw about 10.4-16 mA. The WDC ones are rated at 1.5 mA/MHz, which would give 6mA at 4 MHz.
Mind you, that's probably only useful if you can get the MPUs draw on its own, as the rest of whatever's on the board could possibly be drowning the effect of the thing you're interested in.

I'm curious as to why you want the Rockwell part specifically, though. From my (very limited) knowledge, the WDC part should work in its place(it's rated for 14MHz max), although the WDC one has more opcode, and it's not quite pin-compatible. You'd need to leave a few pins disconnected (specifically, pins 1, 5, 35, and 36), and if whatever you're plugging it into uses the clock outputs, that might possibly throw a wrench in the works. WDC doesn't specify or test those anymore, so those could throw the timing out of whack.

What is it you want them for?

WDC still make genuine 65C02s, which are rated to run up to 14MHz, not just 4. They differ slightly from earlier Rockwell versions, but you should be able to use them.

I have homemade CPU board containing 6502 socket, two 62256 SRAM chips, 27128 EPROM and few additional logic chips (TTL-LS and HCT families). I've tested it with MOS6502 and MOS6502AD (bought on Alliexpress), running at 1 MHz. The entire board was drawing around 150 mA. When tested with R65C02P4 from Ebay (also running at 1 MHz) it drew similar amount of current, some of them even a little bit more (170 mA).



I want CPU that is pin to pin compatible with original 6502, to use it without modifying my existing board designs.

Sounds as though you received counterfeit parts. As others have suggested, I recommend you use the W65C02S produced by WDC and purchase only through an authorized source, not a Chinese seller on eBay. Only trvial changes are needed to adapt the WDC part to an NMOS circuit.

Meanwhile, use eBay's claim system to demand a refund and be sure to clearly state that the components you received are counterfeits. eBay will likely shut down that seller so he (?) can't cheat anyone else.


At 4 MHz, the lag between Ø2 in and the Ø1 and Ø2 outputs is probably very short relative to the 125ns interval between clock phase changes. So he may be able to live with the timing that results.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

What changes should I introduce into my board design, to make my MOS6502 board compatible with WDC65C02?
I've ordered few of those chips. I've read datasheet and as I see pinout is only slightlydifferent:
1) Most important, pin one is VPB output instead of VSS. Should I left it unconnected?
2) Pin 5 is a MLB output insted of NC. It changes nothing, it is still left unconnected.
3) Pin 36 is BE instead of unconnected. It is input, so I assume it should be pulled up to the VCC, by 3.3k resistor.

Is that all? Clock related inputs/outputs are still the same? Should I still use pin 37 as a clock input and 39 PHI2 output for clocking peripheral chips?

Yup
Right.
That's fine. Or just tie it straight to Vcc.
That'll probably be OK, and it's compatible with older CPU's. But WDC offers no timing spec for the pin 39 signal, instead simply suggesting pin 39 not be used. That means the peripherals would instead get the same signal that's applied to pin 37. You could install a jumper if you want the ability to do it either way.

-- Jeff

PS: I overlooked Arne's post, but I agree:

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I will make a new PCB anyway. Is it suggested to clock peripheral chips directly from the main clock output (pin 37 o 6502)?

Yes, pin 37 (which is an input). The signal from the clock source (oscillator) would go straight to CPU pin 37 and also to the clock inputs on peripheral chips.

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I would suggest the jumper option Dr Jefyll suggested for PHI2. And you could add a solder bridge option to GND p1. In case you get some real R65C02 or those from GTE you don't need to rewire anything. (And in case the current draw doesn't bother you, you can use your fake parts as well )

B.T.W. the last R65C02P4 I got when buying a 6502 badge. Perhaps you drop a mail to Lee Hart asking whether he would sell a CPU alone.


Regards
Arne

Ok, now I am sure. I tried to run a code compiled for 65C02 on those chips. It doesn't work correctly in exactly same was as on MS6502.

Just one more question about WDC65C02. What load may be connect to the address bus of this chip? Are buffers required or can it handle driving multiple peripherals directly?

From the "74xx Logic Families and Timing Margins" section of the 6502 primer:

You will not need bus transceivers with a CMOS 6502, especially WDC's current production W65C02S. I have done some brief tests on the W65C816S's pin drivers. Their behavior was pretty much symmetrical, able to pull up just as hard as they can pull down, unlike TTL which cannot pull up as hard. If you had to boil my test results down to approximations and treat the circuits as just a resistance, the data pin drivers acted very roughly like a SPDT switch with 50Ω in series with the common terminal (ie, the output); and the address bus pins, as a SPDT switch with 60Ω in series. I have not had the chance to test a W65C02S; but I suspect WDC used the same circuits on the '02 and the '816, which would make it much stronger than the data sheet says. The time constant of 60Ω times the capacitive load of 10 CMOS loads is around 3ns, which is less added delay than you'll get from a bus transceiver IC. Daryl Rictor had no trouble running my 4Mx8 5V 10ns SRAM module on his SBC-4 single-board computer at 12MHz with a barefoot '816 (ie, no bus transceivers), driving this module and three daughter boards at the same time. The module has 8 bussed SRAM ICs.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Is it specified somewhere in the manufacturer documentation? I can't find any mention in the WDC65C02S datasheet.
In R65C02 datasheet it was mentioned, that address bus line can drive single TTL input, which is basically the same as in original NMOS version.