Where to buy 6502's?

[gnawzie]

I'm not sure if I should look on ebay for these, but I've also noticed these other WDC chips, are those chips the same as 6502 or otherwise compatable?

[Dr Jefyll]

Various companies have produced 65xx CPU's, including MOS, Rockwell, Synertek, WDC and others. You are well advised to select a chip produced in CMOS technology, rather than NMOS. So look for the "C" in the part number.

WDC is the only company that's currently manufacturing a 6502 made in CMOS. Nevertheless, Rockwell and other 65C02 chips are still very widely available and reasonably priced. IMO the WDC product is a good choice if you're an advanced user who can benefit from 14 MHz operation and unique WDC features such as the VP and BE pins.

Otherwise, you will do better with an alternative product -- mainly because the older, slower chips are actually more forgiving in terms of less-than-perfect construction techniques (such as breadboards). This point may seem confusing, so let me clarify. What I'm saying is, you might install a Rockwell 'C02 in your project and quickly find success running at 1 or 2 MHz. But a WDC 'C02 installed in the same project and running at the same speed may fail. The WDC is more demanding in terms of good construction techniques. That being the case, you may wish to defer use of a WDC chip until a future date.

As for Rockwell etc, some people may feel uncomfortable buying a chip that's not of recent manufacture -- it may be NOS, or a "pull" salvaged from a recycled board. But that's no big deal, IMO. If you're seriously that worried about ending up with a defective chip, just buy two. They're cheap anyway, and you may be glad to have a spare.

cheers
Jeff

[BigDumbDinosaur]

Dr Jefyll wrote:

IMO the WDC product is a good choice if you're an advanced user who can benefit from 14 MHz operation and unique WDC features such as the VP and BE pins.

The WDC 65C02 pinout is slightly different than the 'C02s made by the other sources mentioned by Jeff. Pin 1 on the WDC MPU is VPB, whereas pin 1 on non-WDC MPUs is a ground. There's a slight difference in the instruction sets as well, but for most builders, that's inconsequential. Stay away from undocumented opcodes and you'll be fine.

Quote:

...mainly because the older, slower chips are actually more forgiving in terms of less-than-perfect construction techniques (such as breadboards).

What Jeff is alluding to is the very rapid rise and fall times of the WDC 65C02's outputs (and the 65C816). Even at low Ø2 rates, the effect of a sub-nanosecond state change time can cause severe ringing and other maladies. So, Jeff's advice is to be considered if you are unsure about how well you can construct your project.

Quote:

As for Rockwell etc, some people may feel uncomfortable buying a chip that's not of recent manufacture -- it may be NOS, or a "pull" salvaged from a recycled board. But that's no big deal, IMO. If you're seriously that worried about ending up with a defective chip, just buy two. They're cheap anyway, and you may be glad to have a spare.

Jameco is the safest, if not cheapest, source for non-WDC 65C02s. Most of their inventory is Rockwell product and was new at the time of acquisition. Jameco clearly notes in the catalog if a chip is a pull.

[Dajgoro]

I got all of my 6502 chips from ebay, and none of them are defective.

[BigDumbDinosaur]

Dajgoro wrote:

I got all of my 6502 chips from ebay, and none of them are defective.

Are they NMOS or CMOS parts?

[Dajgoro]

BigDumbDinosaur wrote:

Dajgoro wrote:

I got all of my 6502 chips from ebay, and none of them are defective.

Are they NMOS or CMOS parts?

At the time I bought them they were only selling old NMOS chips, but now I see that you can find the CMOS as well.
I even got a Bulgarian NMOS clone(that one was the cheapest of all), and even that one worked.

I ordered a UV photo diode, and when I went to test it I found out that it didn't conduct or generate any electric signals, no matter how I connected it, and upon a closer look, the die was completely black.
On another occasion I bought a old ceramic 8031 and that one was partially faulty, the CPU core worked, but some of the peripherals were dead. Later I got the same chip form another seller and it worked flawlessly.
Good thing about ebay is that if something doesn't work, you can always ask for a refund or for a new item, it is only that you have to wait a bit.

I prefer buying from sellers that have a good reputation such as hkutsource, which actually is a company that just sells stuff over ebay.

[BigDumbDinosaur]

Dajgoro wrote:

Good thing about ebay is that if something doesn't work, you can always ask for a refund or for a new item, it is only that you have to wait a bit.

Bad thing about eBay is you get your time wasted and patience stretched thin when your extra cheap purchase proves to be junk.

[Rob Finch]

I'm not sure how true this is, but I've heard that electronics typically last only about 20 years or so before ambient radiation (and heat) destroys their properties enough that they don't function right. So one might want to be careful about buying older parts. If the parts were well shielded they're probably fine, but when buying older or used parts who knows ?

[GARTHWILSON]

I don't think there's much to worry about for this application. I have plenty of electronics stuff from the 1970's and it all still works except tape recorders and turntables whose rubber belts and wheels have rotted. Just for historical value, I have a cheap portable 3" open-reel tape recorder from the early 1960's that still works mostly like new. In our high-end aircraft intercoms we've been selling for 20+ years, the only things that have gone out with time are 220uF 16V capacitors that had 6V on them all the time they were powered up but their charge voltage was steady, ie, didn't go up and down which I think would have made them last longer. We should have made them 25V but the smaller size was too attractive. None of the 25V or higher capacitors have gone out except the rare infant mortality. On very rare occasion I have to replace a pot that was broken from abuse, or a relay or a switch, but being mechanical, they're kind of in a different category. All the test equipment on my workbench is 30-35 years old, and the only problems have been with dirty pots and switches. The programmable calculator I use every day is 27 years old. The mechanicals on printers and plotters have not done so well.

[BigDumbDinosaur]

NOS chips seem to last a long time, excepting maybe the PLA/PALs and GALs from way back. Most of those seem to lose data retention after about 20 years or so.

I would avoid parts that can't be positively identified as new. You don't know what pulls were subjected to before you get them.

[Dr Jefyll]

Another factor is thermal cycling. A chip that, in the normal course of business, gets hot and then cools down again is at risk due to the resultant expansion and contraction. My understanding is that after thousands of cycles this can lead to mechanical failures such as separation of bond wires from the die. But of course we all use cool-running CMOS chips, right? Hmmm. I once had a VIA that got so hot it burned my finger! -- aka my "digital" wattmeter. That was a CMOS chip, but I'd made a bus contention boo-boo and was drastically abusing the part (which, incidentally, survived ).

BigDumbDinosaur wrote:

I would avoid parts that can't be positively identified as new. You don't know what pulls were subjected to before you get them.

Fair enough. Like you, BDD, I'd rather have a new chip than a pull. But preferences may yield if price or availability is a problem. Myself, I'm still keeping a bunch of chips that are essentially pulls from my own previous projects. Frankly, many of them have been handled & stored somewhat carelessly. But it doesn't bother me to reuse them -- I just make a mental note in case there's trouble. But I don't recall any.

BigDumbDinosaur wrote:

[...] PLA/PALs and GALs from way back. Most of those seem to lose data retention after about 20 years or so.

Good point about data retention. What I'd worry about most are EPROMs and similar chips which rely on a minuscule charge on a floating gate (although chips that use fuse technology aren't perfect either). Of course if the part we're buying is blank (unprogrammed) there's no data to worry about retaining.

I've faced a few troubleshooting situations where I suspected data loss in an EPROM. For example, there was an old Ensoniq keyboard (music synth) that wouldn't always navigate through its user menus consistently -- after the unit had been on for a while the UI would start behaving illogically. The customer had resorted to playing gigs with a small fan blowing on the keyboard! I dutifully pointed out that intermittent problems can be very labor intensive to resolve, so the repair was never performed and the problem never positively identified. But my hunch is that all the EPROM bits had been slowly losing charge over the years, and one or two had gotten so bad they were indeterminate and could be influenced by temperature.

Going slightly OT, I suspect data retention may be a far more serious problem in modern equipment -- particularly Flash memories that use analog voltages to store more than one bit in each individual floating gate. A possible instance of this involves a digital camera I purchased last year. One day it inexplicably lost the ability to turn the reset of file numbering on & off -- the UI no longer lets me determine that particular option. I suppose maybe I could download the firmware and do a refresh. But meanwhile I view the new, ultra-high capacity thumb drives with some distrust...

-- Jeff
ps- Garth, were those tantalum caps you were referring to?

[ElEctric_EyE]

O.T.: Sorry, call me Mr. Off-Topic today.

Dr Jefyll wrote:

...I've faced a few troubleshooting situations where I suspected data loss in an EPROM. For example, there was an old Ensoniq keyboard (music synth) that wouldn't always navigate through its user menus consistently -- after the unit had been on for a while the UI would start behaving illogically. The customer had resorted to playing gigs with a small fan blowing on the keyboard! I dutifully pointed out that intermittent problems can be very labor intensive to resolve, so the repair was never performed and the problem never positively identified. But my hunch is that all the EPROM bits had been slowly losing charge over the years, and one or two had gotten so bad they were indeterminate and could be influenced by temperature....

I used to own an Ensoniq ASR-10. Awesome 32-voice sound machine! When I develop the sound board portion of my beast project, it will be modeled after that one.

EDIT: I wiki'd Ensoniq. Very interesting company. Some folks from MOS headed it up, that was right around my neighborhood (Norristown, Pa) when I was growing up. I used to live near Hatboro which is in close proximity. Funny I never knew all this back then.

BTW, very interesting info on the FLASH vs. EEPROM data retention. Like Garth I have computer silicon, even 5 1/4" 1541 floppy drives from a Commodore C-64 and C-128 that still work to this day... If I were going to build a system that had FLASH in it, I would make it to be able to be programmed from a source that could read the original image from an optical CD-ROM.

EDIT: For all my FPGA projects I do backups of multiple project files on a SSD, with no moving parts. Even then, I spend so many man hours on the project that if the backup medium happened to fail I could probably do it from memory, but I don't want the hassle so I will burn to CD-ROM.

[Justin]

Dr Jefyll wrote:

Good point about data retention. What I'd worry about most are EPROMs and similar chips which rely on a minuscule charge on a floating gate (although chips that use fuse technology aren't perfect either). Of course if the part we're buying is blank (unprogrammed) there's no data to worry about retaining.

I've faced a few troubleshooting situations where I suspected data loss in an EPROM. For example, there was an old Ensoniq keyboard (music synth) that wouldn't always navigate through its user menus consistently -- after the unit had been on for a while the UI would start behaving illogically. The customer had resorted to playing gigs with a small fan blowing on the keyboard! I dutifully pointed out that intermittent problems can be very labor intensive to resolve, so the repair was never performed and the problem never positively identified. But my hunch is that all the EPROM bits had been slowly losing charge over the years, and one or two had gotten so bad they were indeterminate and could be influenced by temperature.

I have a buddy who is a retired nuke plant technician. They had a piece of equipment in their control room that lost its EPROM after ~20 years. I was curious if reprogramming it would have lasted another 20?. Obviously, they didn't take any chances and just replaced it with a new chip.

[Dr Jefyll]

Justin wrote:

I was curious if reprogramming it would have lasted another 20?

Well, we don't know for certain why that particular chip failed; there are various possible reasons. But let's say it is because the floating gates had lost most of their charge as a simple result of normal leakage. In that case I think it could be reprogrammed and reused. But good for another 20 years? That may exceed the specifications as shown on the data sheet. This will vary, of course, but 10 years is a figure I've often seen cited.

FWIW, reprogramming that EPROM as you suggest would in some ways be very much like the refresh of a DRAM cell. But the data retention period on the DRAM cell is specified in milliseconds -- not decades!

Edit:

Quote:

Obviously, they didn't take any chances and just replaced it with a new chip.

What we want is a recently programmed chip -- not one that's new, necessarily.

[GARTHWILSON]

Dr Jefyll wrote:

Another factor is thermal cycling. A chip that, in the normal course of business, gets hot and then cools down again is at risk due to the resultant expansion and contraction. My understanding is that after thousands of cycles this can lead to mechanical failures such as separation of bond wires from the die.

Someone asked Bob Pease about that, referring to the different coefficients of thermal expansion. He's the famous industry guru and analog chip designer who worked for National Semi and who was killed in a car accident a couple of years ago. His response was that the temperature cycling on the bond wires where they contact the die wasn't a problem. The temperature most ICs' dice run at is not very high though. When I was working in applications engineering at the VHF/UHF power-transistor manufacturer in the mid-1980's, I sometimes did infrared scanning of uncovered transistors while they were running under abusive loads. The maximum I ever saw actually running was over 350°C. At that temperature the die might not have lasted even an hour, because of migration of the metalization and other factors; but it does put a new perspective on temperatures.

Quote:

But of course we all use cool-running CMOS chips, right? Hmmm. I once had a VIA that got so hot it burned my finger! -- aka my "digital" wattmeter. That was a CMOS chip, but I'd made a bus contention boo-boo and was drastically abusing the part (which, incidentally, survived ).

I've had a CMOS Rockwell VIA get super hot because of latch-up. Fortunately, it didn't hurt it. It was feeding a printer across the room that was powered by a different circuit, and I guess some kind of spike produced the latch-up.

Quote:

BigDumbDinosaur wrote:

I would avoid parts that can't be positively identified as new. You don't know what pulls were subjected to before you get them.

Fair enough. Like you, BDD, I'd rather have a new chip than a pull. But preferences may yield if price or availability is a problem. Myself, I'm still keeping a bunch of chips that are essentially pulls from my own previous projects. Frankly, many of them have been handled & stored somewhat carelessly. But it doesn't bother me to reuse them -- I just make a mental note in case there's trouble. But I don't recall any.

Of the thousands of unused ICs in my inventory, a few hundred are from a source whose handling I'm not as confident in, so they're kept separate.

Quote:

BigDumbDinosaur wrote:

[...] PLA/PALs and GALs from way back. Most of those seem to lose data retention after about 20 years or so.

Good point about data retention. What I'd worry about most are EPROMs and similar chips which rely on a minuscule charge on a floating gate (although chips that use fuse technology aren't perfect either). Of course if the part we're buying is blank (unprogrammed) there's no data to worry about retaining.

I've refreshed the data in EPROMs of commercial products I have from the 1980's to prevent that problem. I also kept a copy of them on disc.

Quote:

Going slightly OT, I suspect data retention may be a far more serious problem in modern equipment -- particularly Flash memories that use analog voltages to store more than one bit in each individual floating gate. A possible instance of this involves a digital camera I purchased last year. One day it inexplicably lost the ability to turn the reset of file numbering on & off -- the UI no longer lets me determine that particular option. I suppose maybe I could download the firmware and do a refresh. But meanwhile I view the new, ultra-high capacity thumb drives with some distrust...

I don't like to be the guinea pig on anything, including new high-density memories. Our son was one of the first to get a 4GB SD card for his camera, and it went bad right away. I guess now they can do 4GB without having to store multiple bits in one cell. Single-bit-per-cell flash however usually has data-retention specifications of anywhere from 40 to 200 years, which is much longer than EPROM. EPROM was usually guaranteed for ten years and usually went at least 20.

Quote:

ps- Garth, were those tantalum caps you were referring to?

No, just the inexpensive aluminum electrolytics, not even high-temperature. We've never used tantalums in the products. When I worked at TEAC in the early 1980's, the only electrolytics that went out were power-supply capacitors where they used too low of a WVDC to try to save money and space.