Wanted to run a quick one past you all. I heavily use a 6501 in several of my boards designs, and I need a little more horsepower. Can I overclock my 6501(Rockwell) beyond 2MHZ?

Any suggestions?

Thanks,

Neil Connolly
neilconnolly@mediaone.net

My current home-made wire-wrapped workbench computer has a 6MHz 65c802 (I used to have a 4MHz 65c02 in it earlier), three 4MHz 65c22's, three 4MHz 65c51's, 70ns memory, and 74ACT logic. I increased the speed until it began having problems, which came at a little over 7MHz (at room temperature, which is what I always run it at). To have some margin, I put in a crystal clock oscillator that keeps it at 5MHz, and it has run maybe a thousand hours this way, with never a problem. I do not have capacitors across power and ground at the various ICs either, but rather a star-type hookup scheme of power and ground wires, with the 5V regulator and its output capacitors in the center of the board. Some may think this could never work, but it has proven completely reliable.

I'm not the expert here, but it's my impression that the speed a part is spec'ed at is the maximum speed where certain timing margins are guaranteed at the maximum temperature. The part may run quite a bit faster if you if you don't have to run it so hot, and if you use faster glue logic and memory so the timing margins are greater.

If anyone has info on speed versus temperature for things like this, I'd be very interested.

Garth Wilson

_________________
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 this the R6501Q in the 64 pin QUIP package ? The way I understand it from the Rockwell people is , they were all manufactured to be 2 MHZ parts and then tested. The ones that didn't make the tests were sold as 1 MHZ parts. I think they were using a 2 micron process for this parts. The current WDC parts are about .18 micron. I think you would be pushing it to over clock them. I think it would be on a chip by chip basis depending on what other chip delays, memory speed & board layout. Good luck. To get higher speeds you could use thw WDC W65C134
Ted Melton

I just looked at WDC's website again, and some pieces of info are inconsistent; but it looks like the geometry of the actual parts they're selling is .8um. They have a licensee that's running a 6502 core at 50MHz, and they expect that in a few years it will be at 200MHz (dig that 35ns interrupt latency!). But for now, many hobbyists' speed will be limited by the 65c22, which is only spec'd for 10MHz, meaning with good construction, fast glue logic, and holding the temperature down, you may do ok up to as much as 15MHz. The WDC microcontrollers are only spec'd to 8MHz as I remember.

Garth Wilson

_________________
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?

Yeah, but 8 MHZ is still faster then 1 MHZ.
Ted Melton

It seems that nobody recognizes that a 6501, is not a 6502, nor is it a 658-whatever. The notion that a 6501, of whic I've not seen one since 1976, was a 6800 pin-compatible version of the 650x core built to steal market share from the Motorola processor, which was somewhat slower than the 6501 due to the enhancements brought about by the "endian" shift in the MOS Technology part. Some think it was also built specifically as a stalking horse for Motorola to target, to be subsequently offered as the sacrifice concession to Mot. when their less costly 6502 requiring fewer external support parts, was ready for market. I was not aware that Rockwell ever made this part.

I have a very early 6502 that's never been afraid to run at 2 MHz, though, as someone else already pointed out, the timing parameters are somewhat skewed, as the linear delays are larger with respect to the clock pulse widths. You may well have trouble making the normal timing margins work with this device, though you may have less time with data hold time than at 1 MHz.

If you have a datasheet for this part from Rockwell, I'd like very much to see a copy.

The Rockwell parts with which I'm most familiar are the 65C02 and 65C102, which are both alike with the exception of the clock circuits.

Uli

If speed is really what you're after, I'd highly recommend trying to program a Scenix SX52 at 100 MHz to emulate a 650x core. That should get you performance far in excess of what the current makers of the 650x chips can deliver. I see no reason why one couldn't achieve performance between 8 and 16 MHz using a precise emulation of the instruction set.

Uli

Yes, I was aware of the 6501 way back when. But the question of someone using a 6501 now, I just assumed it was the Rockwell R6501Q. I have a few boards I designed aroud it. The R6501Q is a microcontroller with a 6502 core. It has 4 I/O ports, 192 bytes of RAM, 2 16-bit Timer/counters, serial port, 4 ext Interrupts, the bit instructions from their CMOS parts. When it came out in the early eighties, it was a nice part. It was an NMOS part ava. in 1MHZ & 2MHZ.
Ted Melton

I've thought about that option, but not seriously at this time. I don't really have the time to develope it.
Ted Melton

Well, not quite ... the part you're referring to, I believe, is the RC6511Q, which is quite another bird.

Uli

Sadly, and in spite of WDC's claims to the contrary, there's no evidence anywhere that any 6502's (real 6502's not some other part that's similar) have ever been produced that are, in fact, capable of the clock speeds the WDC folks claim. The parts they do seem to sell are not made by them and don't adhere to their spec.

If you want a fast 6502, and I really don't see why one would go to the trouble, you'll have to build it yourself. The NMOS parts, marked 1 MHz routinely ran at 2, though they'd fall down sometimes. I have several of the SYNERTEK 4 MHz NMOS parts that I never did use except at 6.144, 5.0688, or 4.9152 MHz. I also have Rockwell CMOS 65C02's and 'C102's that were spec'd at 4 MHz and that I played with at speeds up to 12. I'd never send out something like that, but it was fun to play.

Uli

Rockwell made a R6501Q & a R5611Q. Both were NMOS parts. The R6501Q had internal pullup resistors on Ports A,B, & C, the R6511Q didn't. The R6501Q was ava. in 1MHZ & 2MHZ parts, the 1MHZ part had divide-by-4 oscillator, the 2MHZ part had a divde-by-2 oscillator. That way you could use a 4 MHZ cyrstal & change the speed of the board by swapping only the R6501Q. The R6511Q had only a divide-by-2 oscillator, if you wanted to go from 1 to 2 MHZ you had to change the crystal, also. Otherwise, the were pin compatible.

Ted Melton

The only parts I have from WDC ( they are a fabless company ) are a 4 MHZ 65816 & 65802 & 65134.

I'e got some parts from Rockwell, a R65C19 that runs at 10 MHZ, it's a continuation of the microcontroller line that wasa developed for Modems. I also have a couple R65L39's ( scanvaged from Modems ) that run at 20MHZ. A lot od 14.4 Modes have either the L39 or C40 Rockwell microcontrollers. They're in 84 pin PLCC packages. They've got up to 1470 bytes of RAM, 5 I/O Ports, 2 16 bit Timer/Counters, 2 17 bit time generators, a USART, among other things. If you find any of the chips, I've got a copy of the DATA sheet. It's about 130 pages.
Ted Melton

Unfortunately none of these parts are 65C02's. WDC claimed at one point that they made 65C02's that ran at speeds of 14 MHz, and I got word from Mike Naberenzy (sorry if I misspelled that, Mike) that they made one that ran at 20. Unfortunately, though I was at one point preparing to resurrect an existing application that would have meant several thousand parts, they didn't offer to sell me the parts, so I used a different MCU in a different (new) board. It would have been nice to use the old board and old code, all the while exploiting the faster clock rate, though.

If it's got to have new code, it's much easier to use a part that has more features targeted at the job at hand.

Uli.

I looked at the microcontrollers because I was desighning new boards. I wasn't just trying to speedup an existing board with a 6502 socket.
I saw an advantage of the Rockell & WDC microcontrollers in that they used the 6502 assembly language. Whereas other brands changed the assembly language when going from a microproccesor to a microcontroller.

What other processor did you change to ?
Ted Melton