somebody told me that this cpu is difficult to get. Is because i want to go from 5 Mhz to 10 Mhz. The one i have is just a 65C02P. Can i just overclock it or i have to change it for the 65C02P-8

best
Ricardo

It seems like there should be an additional digit after the P, indicating the speed. Who made it? The marked speed is the minimum speed where it is guaranteed to not only work but also meet the timing margins in the data sheet. It will probably work a little faster, and it may work a lot faster. I don't think I've ever heard of one specified for 8MHz though. I've heard of 4, 6, 10, and 14MHz, and WDC's current production is guaranteed to do at least 14 but most of them can run at 24MHz at room temperature-- if the rest of the circuit can support it. That "if" is a major factor though, and just because you get a faster-capable processor doesn't mean you can squeeze much more performance out of the whole computer.

Some years back WDC dropped their $100 minimum order, but some who have tried to buy small quantities have recently indicated that WDC was not very responsive. That's somewhat understandable, since WDC is mainly in the business of licensing 65xx IP, not selling the hardware. I would call them up with credit card in hand and be ready to say, "I want to order three of this and five of that" etc.. I did that quite a few years ago and got instant results; but if hobbyists take too much of their time for small orders, it is understandable that they won't look very favorably on that.

There's also a U.S. distributor, Apatco that someone said had 65xx parts but I don't see any there for sale now. Mike Naberezny who runs this website may be able to sell you some.

It sounds as though he may be thinking of a part sold in the early 1990s. That number was on the MPU that was in a terminal server for which I wrote a BIOS and other code. The 'P', if I correctly recall, meant a PDIP40 package. It wasn't until the mid-1990s that WDC converted everything to a fully static core, which was represented with an 'S' in the part number (e.g., W65C816S).

In those days, WDC did sell different speed grades (faster = more money, of course), and the speed stamped on the package was the maximum at which the MPU was guaranteed to perform and stay within the timing specs. Wafer yields back then were not as consistent as they are now, so I suspect a certain amount of "cherry-picking" went on to determine just how fast a given part could run before messing up.

With today's MPUs, the F Max vs. VDD curve (page 27 of the data sheet) suggests that all current parts are capable of 20 MHz, assuming reasonable cooling. Of course, as Garth said, a circuit that can support that speed is de rigueur.

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

Dear sirs,

Thanks for the answers. What i have is a small chess machine that have this type of processor. For the moment i do not have it with me, but i will look at it and post in this forum the exact ID of the processor and the RAM. I am trying to do an upgrade to 1O Mhz of this machine and somebody is selling me the ROM with the software loaded. He also told me that i have to change the processor for the one i mentioned and have to change the RAM for a faster one like an HM6264 (e.g. LP70 = 70ns).

best regards
Ricardo

70ns may not be fast enough for a 6502 to run at 10MHz. With a good design, the next faster speed, 55ns, is barely fast enough, if you have really fast glue logic. Yes, that period is 100ns at 10MHz, but then from pages 25-26 of the data sheet, you have to subtract the 10ns data set-up time, another 10ns address hold time from the previous cycle, plus time for the processor to come up with and output the next address on the bus. The specified access time for 14MHz is 30ns, and running it at 10MHz gives 28 more ns, guaranteeing you only 58ns, and some of that is going to be taken up by the address-decoding logic. In truth, a SRAM marked 70ns will probably be somewhat faster although not fast enough to have been marked 55ns, and the processor can usually run faster than it is specified to as well, but it is not guaranteed to. There may be other things that will limit the speed too, including ROM, glue logic, and I/O. What I would do (and have done) is to put the fastest parts I can in, then slowly increase the speed until the computer starts having problems, then back the speed down about 25% for reliability.

Also, the PCB layout may give rise to problems as you ramp up Ø2. You could experience crosstalk between traces, crosstalk between layers, inadequate bypassing, ground bounce, etc. It's amazing what starts to act up as the clock rate goes up.

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

For the moment i can only see the ID of the RAM that is SRM2264LC10 the exact ID of the processor i can not see but i can find out.

[img][img]http://img97.imageshack.us/img97/1951/polgarcpu.png[/img][/img]

I could not find out wich type of 65C02 i have in that board, the top ID label of the 65c02 chip had been erased but i know for sure it is a 65C02.
Does anybody knows where i can find the old datasheet of the 40 pin 65C02? or if the 65C02 is 100% pin compatible with the WDC65C02S 40 pin package?

If i leave pin 1 of the WDC65C02S grounded, can it work?

Sorry 100% pin compatible with W65C02S.

There are data sheets at http://www.6502.org/documents/datasheets/ .


The WDC data sheet is there too, at http://www.6502.org/documents/datasheet ... 4_2009.pdf . The main thing with the WDC that might not be compatible (but easily corrected) is that pin 1 of the WDC 65c02 is not ground, but rather a vector-pull (VP\) output. If necessary, you can bend the pin out just enough that it doesn't make contact in the socket. WDC's also has a memory-lock (ML\) output on pin 5, but your socket probably has no connection there, and a bus-enable (BE) input on pin 36, which your socket also probably has no connection on. The BE input has a weak internal pull-up, but you might want to add a stronger one externally. 20M pull-up is awfully weak!


BTW, instead of adding another post to cover something you forgot, you can click "Edit" in the top-right corner of your post (when you're logged in) to make changes and additions to something you've already posted.

Apatco assured me they'd be putting links to the 65xx chips where everyone can find them. Obviously, they don't wish to sell chips.

Try:

http://stores.ebay.com/Littlediode-USA
http://www.littlediode.com/

I am not him, have no connection to him, but i CAN find the part numbers on his ebay and private website.

Same for here:

http://stores.ebay.com/Telec-Electronics

which turned up 36 hits searching for 65* there.

aikatt

Anyone paying their kind of prices must not know they can buy the modern, faster, better parts from WDC at less than half those prices. It wouldn't be bad for me if I could sell my 110 6512's for $18 each!

But i know i CANNOT buy chips from WDC, i've tried.

aikatt

Navigate to their online shop and then Replacement Components » Integrated Circuits.

Did you follow the advice Garth gave to you last time?

It's best to behave like an easy customer. It's better not to be quick to criticise on a public forum.

Treat your suppliers like people and consider their costs in selling you a few tens of dollars of product.

Until you place that order for hundreds or thousands of parts, the profit they stand to make is barely worth their time.

These suppliers aren't supermarkets.