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

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eslapion
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Re: The end of the ROM based PLA for the 64

Post by eslapion »

Since the posting by Mr. Schönfeld of a screen capture purportedly showing massive short bursts of multiple signaling on the M27C512-90B6 when used as a PLA in the C64, it has become necessary to dispel false informations and myths about this IC and how it behaves.

It is now installed in hundreds of C64 and has exhibited a level of compatibility higher than the SuperPLA V3.

Here are a few logic analyser captures showing clearly there is no "bus contentions" as proclaimed.

This first capture shows a C64 with board 250466 running with this IC as PLA.
Image
There is one occurence of multiple signaling in this graphic - its a write access to the color SRAM and is therefore part of the normal operations of a C64.

This second capture shows the PLA outputs activity while the cartridge Super Zaxxon from SEGA is running in demo mode.
Image

As I said and can now prove, if we are to assume the circuit obtained is genuine then the only way to obtain the type of outputs that can be seen on the graphic obtained by the friend of Mr. Schönfeld is to cheat with numbers - set the threshold level unreasonably high.
Image

I believe this is proof enough that this is a complete fabrication. An easy one too.
wiesel wrote:Now that we know that the number of CMOS devices on the same data bus cannot be limited by the PLA that you are providing, you need to guarantee that your PLA device will never pull two (or more) select lines low at the same time.
It cannot be limited by the PLA that I provide because it cannot be limited by ANY PLA at all. Even Commodore's own made PLAs can, for very brief periods of time will pull two select lines low. This problem can be compounded if very fast ICs are used as kernal replacements or in cartridges.

This problem is alleviated when the PLA used will generate a brief "dead time" when switching from one select line to another. Something the ST PROM does. Not so with the 82S100, the 7700 and the 8700.
As measurements by Tommi and me are showing, this cannot be guaranteed with an EPROM-based PLA.
The measurements you provided were clearly fabricated and I was able to do the same thing.

ADDED EDIT:
The original picture concerning the M27C512-90B6 (apparently purchased from UT Source) behavior as a PLA was changed.

While the original (link here ) did not show the threshold voltage or capture rate, the new capture shows a capture rate of 100MHz and a threshold voltage of 2.5 volts.

Although this setting is still inadequate for TTL-LS technology (Skoe used 1.3 volts in his analysis called "PLA Dissected"), it shows multiple signaling that nether Skoe, who also used a 100MHz capture rate, nor myself using the Intronix Logicport at a capture rate of 500MHz could mange to find at various threshold levels as seen above.

This leaves only one possibility AFAIK, the person who did the capture for Jens Schönfeld, assuming this person was honest, obtained circuits
that were counterfeit.

I did notice in the past that the circuits sold by UT Source have a type of pin 1 indicator notch that is quite different from the units I have purchased from Mouser between 2008 and 2011. Mouser certifies the components sold are genuine.

Jens Schönfeld, surprisingly did defend a threshold level of 4.7 volts as being adequate. Since the previously posted oscilloscope capture clearly indiquate all types of Commodore original PLAs don't signal above 4.3 volts, I find this claim quite troublesome. Skoe found numbers that are even lower.
Last edited by eslapion on Fri Jul 10, 2015 3:03 pm, edited 3 times in total.
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Re: The end of the ROM based PLA for the 64

Post by e5frog »

eslapion wrote:
As measurements by Tommi and me are showing, this cannot be guaranteed with an EPROM-based PLA.
The measurements you provided were clearly fabricated and I was able to do the same thing.
:-)
You were able to fabricate measurements as well?

Why would they make it up, are everyone measuring the same thing in the same way and use instruments that can be trusted?
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Re: The end of the ROM based PLA for the 64

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Why would they make it up
you didnt get the memo about the anti eslapion conspiracy? check your sources!
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Re: The end of the ROM based PLA for the 64

Post by eslapion »

e5frog wrote::-)
You were able to fabricate measurements as well?

Why would they make it up, are everyone measuring the same thing in the same way and use instruments that can be trusted?
1. They made it up to protect their little cash cow and to make sure the ST M27C512-90B6 would become discontinued before too many were sold.

2. The instruments can be trusted - its the setting that's wrong. Look at the value in the circle. For TTL level technology, this setting should be 2Volts or lower.
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Re: The end of the ROM based PLA for the 64

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Why would they make it up...?
The objective of Jens Schönfeld (and his devout followers) appears quite simple to me.

What he wants is to replace as many original Commodore PLAs as possible with the SuperPLA that he sells. Unlike old Commodore made PLAs which signal their output at about 0.5-4.3 volts, new CMOS chips signal their output at a near full 0-5V. This is also called rail-to-rail output.

One day he's going to come up with a new cart or whatever device that everybody wants, perhaps even alter something he's already selling and these new things, whatever they are, will require a full rail-to-rail output from the PLA - more than likely because they use CMOS technology not designed for TTL levels compatibility - something Commodore made PLAs cannot do. He can then push everyone into buying the SuperPLA because IT signals its outputs at rail-to-rail levels.

However, there is a problem if somebody has installed in his C64 a PROM based PLA which performs really well, such as the ST M27C512-90B6. This chip is the best of both worlds because it is fully compatible on input with TTL levels signals and it too signals at rail-to-rail levels output and will be fully compatible with the new toy in town while being fully backward compatible with everything done in the past. Yet the person who has that kind of configuration did not pay the outrageous price Jens' charging for his SuperPLA. In fact, the ST PROM costs less than 2 euros when purchased by itself.

Whether it comes from me or anyone else, whether its from ST or any other manufacturer doesn't matter at all. A good PROM based PLA is the enemy to kill.

BTW, Groepaz, why don't you tell us why you were kicked out of Lemon64.

ADDED EDIT:
Remember the C64r has CMOS technology on it instead of the original TTL LS chips. Are these CMOS chips fully TTL level compatible? It would be very easy to configure the 64r to damage original PLAs and force customers to replace them with the SuperPLA since you're not allowed to use PROM based PLAs.
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Re: The end of the ROM based PLA for the 64

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BTW, Groepaz, why don't you tell us why you were kicked out of Lemon64.
Why don't you stop posting nonsence claims for once? I was never "kicked out". Infact i asked TNT and Mayhem to delete my account, to protect myself from getting involved into discussing more of your bullshit claims.
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Re: The end of the ROM based PLA for the 64

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groepaz wrote:Why don't you stop posting nonsence claims for once? I was never "kicked out". Infact i asked TNT and Mayhem to delete my account, to protect myself from getting involved into discussing more of your bullshit claims.
That's typical you Groepaz. When faced with undeniable facts, you reply with insults and personal attacks.

You can convince the people who lack the knowledge of whatever falsehoods you want but you can't convince a logic analyser to adhere to your mythical creations.

Why set the threshold level of a logic analyser to 4.7 volts other than for the purpose of disinformation? An honest mistake? I don't think so - the portion of the screen capture that would have shown that was purposely cropped.

You lied - you got caught. As simple as that.
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Re: The end of the ROM based PLA for the 64

Post by groepaz »

1) i never ever lied to you. and my reply was purely related to your nonsense claim of me being kicked out of lemon.
2) i will no more discuss any technical issues with you, as its a pointless exercise and i have better things to do than wasting my time that way.
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Re: The end of the ROM based PLA for the 64

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groepaz wrote:... i will no more discuss any technical issues with you, as its a pointless exercise and i have better things to do than wasting my time that way.
Thanks you and most importantly... goodbye!
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Re: The end of the ROM based PLA for the 64

Post by groepaz »

are you going already?
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Re: The end of the ROM based PLA for the 64

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groepaz wrote:are you going already?
This thread is about technical issues. You clearly said you wouldn't discuss that with me so whatever else you may choose to post here is... pointless.
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Re: The end of the ROM based PLA for the 64

Post by groepaz »

oh sorry. it appeared to me that in the last page(s) it turned into pure bitching and shit throwing. clearly my fault.
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Re: The end of the ROM based PLA for the 64

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groepaz wrote:oh sorry. it appeared to me that in the last page(s) it turned into pure bitching and shit throwing. clearly my fault.
You bitch and you throw shit.. that seems to be your area of expertise.

I reply with actual instruments readouts. I said what I think about this kind of echange to Jim Drew...

http://www.lemon64.com/forum/viewtopic. ... 7&start=11

As I said... You lied, you got caught, now please go away.
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Re: The end of the ROM based PLA for the 64

Post by groepaz »

You lied, you got caught
and thats you not throwing shit. understood.
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Re: The end of the ROM based PLA for the 64

Post by joshuadenmark »

Please bring some love back to this thread guys :wink:
We are all here to enjoy - not fight.

Nice evening to all.
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