The Dos and Don'ts of using an EPROM as PLA in a C64.

Disk drives, Monitors, SuperCPU etc.
banman
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

..........continued from the last post..

Genuine ST 27C512-90F1 vs ST 27C512-90F1 B88AY 9605C SINGAPORE knockoff
DSCF4046Genuine ST 27C512-90F1 vs ST 27C512-90F1 B88AY 9605C SINGAPORE knockoff.JPG

Ruler comparison
DSCF4057 Ruler comparison.JPG

I do think the VPP voltage is a little high. I think the Datasheet says 12.75V


mini pro burn settings
mini pro burn settings.jpg

One will notice that the die images will shine different colors in different pictures. I think this is the way I have angled the camera lens depending on the light.

A full test with an oscillisocpe is needed to get a clearer picture.


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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

Another chip..........


So does this chip passes eslapion's PLA test circuit. It is a knockoff (fake),

ST 27C512-90F6 5880X 9806E SINGAPORE knockoff UV EPROM.

Interestingly , I took some comparison photos of these chips with the genuine ST 27C512-90F1 from the electronics store.

Notice that the knockoff (fake) chips have a different manufacturing process to the genuine one. The genuine die is maybe 2-3 times smaller that the knockoff (fake) ones.




ST 27C512-90F6 5880X 9806E SINGAPORE knockoff UV EPROM SUCCESS
C64 PLA Project ST 27C512-90F6 5880X 9806E SINGAPORE knockoff UV EPROM SUCCESS.jpg

ST 27C512-90F6 5880X 9806E SINGAPORE knockoff vs Genuine ST 27C512-90F1
DSCF4054 ST 27C512-90F6 5880X 9806E SINGAPORE knockoff vs Genuine ST 27C512-90F1.JPG

ST 27C512-90F6 5880X 9806E SINGAPORE knockoff vs Genuine ST 27C512-90F1
DSCF4055 ST 27C512-90F6 5880X 9806E SINGAPORE knockoff vs Genuine ST 27C512-90F1.JPG

One will notice that the die images will shine different colors in different pictures. I think this is the way I have angled the camera lens depending on the light.

A full test with an oscilloscope is needed to get a clearer picture.




I will go out on a limb here and hypothesize about these chips.

I think that these chips are with out a doubt non genuine. Visually, the manufacturing processes are different between the genuine and the knockoffs (fakes).

I think that the original circuit design has been copied along with the inherent characteristics of the genuine ST EPROMS.



All these chips are available from the 2 sellers mentioned in earlier posts.....


I am still testing the other chips. I will report on the other chips soon....
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by eslapion »

banman wrote: Sat Jul 13, 2019 3:27 am ..........continued from the last post..

Genuine ST 27C512-90F1 vs ST 27C512-90F1 B88AY 9605C SINGAPORE knockoff
That's one helluva nice find!! The die is so different.

Can't wait to see the results on the scope.
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

Hi eslapion,



I am dead keen on getting some oscilloscope readings as well.... :D



Here is a picture of the chips I just recently got from the Chinese seller that is mentioned in an earlier post (RenKe zhuang https://huongke.en.alibaba.com/?spm=a27 ... 3e5fJDCbeD).

DSCF4040 Delivery 8pair various EPROMs 12_07_2019.JPG
DSCF4041 Delivery 8pair various EPROMs 12_07_2019.JPG
DSCF4042 Alibaba Delivery 8pair various EPROMs 12_07_2019.JPG

These will be the ones that I will testing time permitting....


So far the ST 27C512-90F6 5880X 9806E SINGAPORE knockoffs (fake) and ST 27C512-90F1 B88AY 9605C SINGAPORE knockoffs (fake) from this delivery and seem to pass eslapion's PLA test circuit.. :D
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by eslapion »

banman wrote: Sun Jul 14, 2019 5:41 amThese will be the ones that I will testing time permitting....
On your photos, the ones that look the most like the real thing have the code CHN on them.
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

Hi eslapion,

Yes, they do look similar.

One will notice that the chip orientation notch on the knockoff (fake) ST M27C512-90B6 chip has a more semi circle shape to it than the original. I feel the printing on the knockoff (fake) is off to the right more than the genuine as well.

The same semi circle shape to the orientation notch seems to be present on all the knockoff (fake) chips. As does the case molding on the black window-less OTP PROM's. They all look all the same.

The knockoff (fake) ST M27C512-90B6 chips made in CHN look like the same plastic case as the knockoff (fake) ST M27C512-90B6 chips made in KOREA (look at the picture in the above post).

The knockoff (fake) ST M27C512-90B6 chips made in KOREA in my above post are the same brand of chips that I initially purchased from a totally different supplier. This time I bought from another supplier to see if there were any differences between my first purchase and this purchase of chips).


I saw one seller that had a chip similar to the genuine ST M27C512-90B6 however it had a 'MYS' as the place of manufacture. As well as the semi circle shape to the orientation notch.
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by eslapion »

banman wrote: Tue Jul 23, 2019 8:31 amOne will notice that the chip orientation notch on the knockoff (fake) ST M27C512-90B6 chip has a more semi circle shape to it than the original. I feel the printing on the knockoff (fake) is off to the right more than the genuine as well.
Correct
I saw one seller that had a chip similar to the genuine ST M27C512-90B6 however it had a 'MYS' as the place of manufacture. As well as the semi circle shape to the orientation notch.
Real ST PROMs carry the country fabrication code TWN which stands for Taiwan so a code like MYS probably means Mystery... :lol:
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

Hi eslapion,

Absolutely! :lol: :lol:




Very briefly on a slightly different topic.

I have been down to the electronics store near me a few times now. He needs to vacate the premises in approximately 1 month. He owned the freehold as well as the business. He is getting to old to carry on.

I managed to get my hands on what I believe are some genuine EPROMs. Please note these are not a suitable size for PLA substitutes. I will probably use them in my game cartridges.

I thought them interesting as an exposé on what genuine chips look like as compared to the many many Knockoffs that are out on the market today.

I found this ST 27C256 windowed EPROM still in its unbroken original packaging. Notice the yellow aging on the plastic tube. From the date code on the Chips it looks like 35 week of 1999. If you look at the packaging it has retention pin spots in several different positions. This tube holds 13 chips. I don't think they have ever been opened. There is heaps of dust on the tubes too.

DSCF4076 cropped.JPG
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DSCF4078 cropped.JPG
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I found some windowed Intel EPROMs dated 1983 & 1983 (27C128). They have a very large die in them. They have undoubtedly been pulled from a circuit board. One can see the remnants of a window protection sticker and there is some scuff marks on the chip legs.

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Here are a few more varieties of EPROMs from different manufacturers.


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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by eslapion »

@banman
A nice treasure trove! One man's trash is another man's treasure!

Just be careful with those 27128/27C128 because most of them require different programming voltages and algorithms.

In there, I see:
27128, 27128A, 27C128, 27128D and all are programmed differently.
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Re: The Dos and Don'ts of using an EPROM as PLA in a C64.

Post by banman »

Hi eslapion,


Thank you for that information on the different programming algorithms for the various 27128 EPROMs. I never knew that. I will be double careful and research before I use them.
I may touch back with you on this matter when the time comes. :D


Just after I posted the last message. I had a bit of free time. SO I did a dragnet on the electronics store.


This is what I came up with.......




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I don't even know what half this stuff is... I didn't know they made EPROMs in a gold line package...

Different stuff coming up from the service dept. daily I am told....



Hello little fellas!!! :shock: :shock:

DSCF4106.JPG
DSCF4113.JPG
DSCF4114.JPG

There is only 4 :-(. :evil:

I have a feeling it's only a flash in the pan. However I will keep looking. :cry:



There is a varied selection of what I strongly believe are original 27512 EPROMs.

This will provide a good test reference for checking out the Glitch when I manage to get the oscilloscope up and running....

I think having a genuine ST 27C512 very similar to yours on hand will be a benefit when comparative testing on the same oscilloscope is run against the newer Knockoffs (fake) ST 27C512 90B1..B6's..FX1 from China.

My way of thinking is even if the oscilloscope isn't dead actuate at least all the results will out by the same margin. That is my guess anyway.....
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