Not quite... The end of the ROM based PLA for the 64

[eslapion]

Do you have shots of what a genuine label may contain?

Label ?? The actual IC is physically different.

The main difference is the notch identifying pin 1 direction. There was a couple of photos through this thread be they conveniently appear to have been replaced with a small icon and the word 'image'...

The real IC can be seen here: http://elcodis.com/parts/653957/M27C512 ... 26014.html

Added edit: Another image source of the genuine IC: https://picclick.com/M27C512-512-Kbit-6 ... 05848.html

Added edit: The images making the difference between genuine and fake appears to have been purposely removed!!
http://sleepingelephant.com/ipw-web/bul ... 1&start=35

Added edit: On this forum, a guy uses a fake M27C512-90B6 and whines it doesn't work... http://retrowiki.es/viewtopic.php?style ... 4&start=16

[norm8332]

I concur that the ones pictured are fakes. The indention denoting pin 1 being the wrong size as eslapion points out. Other giveaways are the two round indentations, as well as the pin 1 indention should have a smooth texture. The laser etching is wrong - wrong fonts and locations.

They re-mark chips in many cases by first sanding away a thin layer from the top of the chip, spraying it with a textured material (usually epoxy), tinning and/or media blasting the pins, then laser engraving the chip as desired. I have noted in my investigation of chips I received from china sellers that many of the remarked ones seem to be old Russian produced clones recovered from discarded equipment and sometimes have non-standard programming voltages. Others are just used old chips of various manufacturers that are cleaned up and re-marked to make them appear new. For example in one instance under a microscope through the window of chips marked ST, I noticed AMD, ST or no mark on the die with all chips from the same batch and same markings.

Some chips are completely fake and may not even be the chip that they are marked as.

You have to remember that labor in China can be very cheap.

[banman]

Hi eslapion and norm8332,


Thanks for your most valuable input on this topic.

I did notice that many images in this forum were not viewable. Not sure as to the reason. I appreciate you taking the time to repost valid images as a benchmark comparison.

Yes, the chip's orientation notch is clearly different size.

I have a Winbond w27C512 45ns chip and compared it to the suspect ST 27C512 90B chip I have.

That notch is identical to each other. The printing on the 2 different chips looks suspiciously like the same ink, color shade, application method.

The 2 round indented holes that are on each chip however are of a different width. I will try to up load the 2 side by side.


Interestingly I found this link on the internet.


https://www.hackup.net/2018/04/retro-repair-addendum-i/

It references a discussion you have checking 2 lines from the cartridge port.

The image in the link in a bit shaky. I don't suppose you might have a clearer image to upload and or a schematic ?



I think I have most of the parts in the picture except the breakout cartridge board. I suppose I could run some tiny test clips from the back side of the cartridge expansion port.


I would like to pursue this as much as I can with my limited electronic / engineering abilities.

I appreciate all the comments, thanks......

[banman]

Here is some pictures of the 2 chips side by side.


Notice that the printing on the chips look oddly similar...

Looking at the ST chip it even looks likes a bit of spray found its way into the 2 recessed holes!


The orientation notch is also the same..

[Mike]

Added edit: The images making the difference between genuine and fake appears to have been purposely removed!!
http://sleepingelephant.com/ipw-web/bul ... 1&start=35

The forum allows to attach images for quite some time now *), so there's a better alternative available now - rather than relying on external image hosters which generally don't guarantee to host the data for an indefinite time.

Seeing that post of yours is from 2016 (which predates said facility of Denial, IIRC), you might want to edit the post and re-attach the images with the forum functions.

Greetings,

Michael

*) not only at the end, images can also be inlined

[banman]

Hi Mike,

Thank you very much for clearing that up. Much appreciated for the information.



Hi eslapion,


I was looking at a write up on hackup.net and viewed this video. Very interesting!


https://m.youtube.com/watch?v=p0r158FDf ... e=youtu.be


My internet connection is a bit dodgy and I have trouble making out some of the component connections this video.

I found this video (yours I believe) which has the schematic if anyone's interested in making one.

(after 17:46):

https://www.youtube.com/watch?v=ofg33zk9uCA


Here is a screenshot of what I think is the schematic to test for a glitch on an eprom pla.


I have ordered some parts to build this. It will most likely take a few weeks for the parts to arrive.

Can you confirm this is correct please eslapion.

If you have any comments or suggestions I would be greatly appreciative.

[eslapion]

I found this video (yours I believe) which has the schematic if anyone's interested in making one.

(after 17:46):

https://www.youtube.com/watch?v=ofg33zk9uCA


Here is a screenshot of what I think is the schematic to test for a glitch on an eprom pla.


I have ordered some parts to build this. It will most likely take a few weeks for the parts to arrive.

Can you confirm this is correct please eslapion.

It's not my video at all, this is a video of me at WoC in December 2017 and the schematic is correct.

Credits for the video go to MindFlareRetro.

[banman]

Hi eslapion,

Great, thanks for that information.

Most Informative.

Let's wait and see what I discover about these chips...

[eslapion]

Hi eslapion,

Great, thanks for that information.

Most Informative.

Let's wait and see what I discover about these chips...

Remember the explanations in the video: The C64 will check for the presence of a cart at power up and this will turn on the LED.

If you reset it and then it turns back on then the PLA generates glitches.

[banman]

Hi eslapion,


Thank you for that extra important information.

This will help me perform the correct test procedure.

[banman]

Hi eslapion,

Apologies for not posting earlier. Work's been frantic and Easter was a busy time for me.


The parts arrived and I have made the test circuit up.


Before we continue this discussion.....

Could you please look at the pictures I have uploaded to check that I have indeed constructed your Eprom PLA test circuit correctly? Thanks



I used an existing 8kb ROM cartridge circuit to take off the 5v and GRN as well as ROM hi and ROM lo. They can be seen in the pictures printed on the circuit board. I checked these against a wiring diagram for the C64 expansion port and appear to be correct.

I found this to be useful as I am not a skilled person by any means.

The Red/Brown wire goes from ROM lo to Pin 11 on the 74LS279 IC breadboard.

The Yellow/Black wire goes from ROM hi to Pin 12 on the 74LS279 IC breadboard.

Pin 10 runs thru the switch to Ground.

Pin 9 goes thru a 500 ohm resistor and LED to Ground.

Pin 8 is Ground.

Pin 16 is 5v.


There is a whole bunch of resistors at one end of the breadboard. They serve no purpose to the circuit and are not connected.

I just used it a place to park them so I wouldn't misplace them.

My construction skills are not very good.

I need to make sure that what I am reporting is accurate to the best of my abilities.

If you think I have it right I will upload videos of 3 different PLA's . Very interesting!

[eslapion]

The IC is correct but concerning your request of me checking your connections, all I see is a bundle of wires. I cannot use a continuity tester on your photos!

Me, when I did that test circuit, I soldered the tiny pushbutton, resistor and LED directly to the 74LS279 and used 4 very small alligator clips to the cartridge port connector leads. This requires opening the case and no actual cartridge board.

Also, if you use a 500 Ohms resistor, the LED will be dim and probably quite difficult to see when it lights up.

[banman]

How very true you you are!

I have gone over the circuit I made numerous times to make sure I have it correct to your schematic.

The LED is visible but not super bright as you predicted.

Here are some youtube links to some videos I took recently regarding the EPROM based PLA solution



https://www.youtube.com/watch?v=cMzcvTi ... e=youtu.be

https://www.youtube.com/watch?v=LaBf4N3 ... e=youtu.be

https://www.youtube.com/watch?v=fRx9tTq ... e=youtu.be

https://www.youtube.com/watch?v=_jODPG_ ... e=youtu.be




I have made some more longer ones with different board revisions.

I will upload these if I haven't already bored the pants off you with my home movies.. Ha.....

{EDITED: 1047pm 22/05/2019 : All the above YouTube videos are giving false results due to incorrect wiring}

[eslapion]

There is a serious problem with 3 out of 4 of your videos.

If the LED doesn't turn on when you power up your C64 then your test circuit is faulty.

Only the first one is a valid test.

[banman]

Hi eslapion,


Yes, you're right! I can't believe I made such a simple mistake in the wiring.

I will say that ALL of the above videos I posted above are giving wrong results.

Remember the explanations in the video: The C64 will check for the presence of a cart at power up and this will turn on the LED.

If you reset it and then it turns back on then the PLA generates glitches.

The problem isn't on the breadboard. It is on the cartridge PCB.

After looking through Sukko Perra'a extensive documentation.


https://github.com/SukkoPera/OpenC64Cart


I had neglected to the close EXEROM jumper pins. Without it the ROM hi and ROM lo lines won't operate correctly.

I have remedied this silly error, and will upload videos with the updated wiring.





Thank you for your help and patience in this.