Denial

Hi eslapion,

eslapion wrote:The M27C512-90B6 is "One Time Programmable". So 'not like yours' ??

Oops apologies for the typo..


It should have read:

I gave my one a go (not realizing they are OTP , like yours). This one worked much better by a long shot..

I was typing too fast...

Hi bdk6, Thank you so much for that information. Especially the assembly plants information. :D You may have solved a big suspicion I have been harboring regarding these knockoff (fake) ST M27C512-90B6 EPROMS we have been looking at. IMG_20190518_102555 (1).JPG Look carefully at the picture above of...

Hi eslapion and bdk6, I have a question.... I just got an eBay message from Little_Diode in the UK regarding the 74HC279 Integrated Circuit for the upgrade on eslapion's PLA test circuit... This is the picture sent sent me.... s-l1600 74HC279.jpg Do you think this 74HC279 looks legitimate? If it doe...

Hi eslapion, Absolutely, I had set out to improve my soldering skills by making C64 cartridges. The 8kB multi cartridge from Sukko Perra. https://www.pcbway.com/project/shareproject/OpenC64Cart_V2__8K_.html Go there you'll see me banging on about the cartridges. I also made up some Multi kernal repl...

Hi eslapion, Thank you for the corrections in my explanations and additional information. Much appreciated. :D Thanks for posting a better looking circuit diagram of your test circuit. I do know for a fact the ST M27C512-90B6 is absolutely not the only 64kx8 memory chip with the adequate properties ...

Hi bdk6, I have too much stuff and too many computers already. But I am always up for learning new stuff. That doesn't take up much space. I couldn't agree more with you there. What were the more daring things you did with the VIC? The test circuit that eslapion has designed is quite cunning. The mo...

Hi bdk6

If anything watch the video Mindflare Retro recorded.


https://youtu.be/ofg33zk9uCA

I found it very informative.. On PLA's that is...

What was you favorite VIC game?

Hi bdk6

Hey... The Vic is mine too..

Not happy when I had to donate it to the local op shop to clear some space in the house..

I had a laminated sticker badge with the 2 prong 9V AC adapter.


You are more than welcome to join in the discussion...it's the only way we learn and go forward.

Hi eslapion and bdk6 Thanks bdk6 for the info on the chip logos. Very much appreciated. I will book mark that site for future reference. Toshiba are a good brand name. I just saw you post on the oscilloscopes too. Thank you. Your input is most valued bdk6. :-) What is your favorite retro computer? I...

Hi eslapion, OK I see. Very good. Replacing 74LS chips of the C64 board with 74HC (CMOS style) ones is definitely ruled out. I see what you mean by the 74HC279 being hard to come by. I looked everywhere! Some Chinese sellers have no writing on the chip whatsoever! I did find some links here on eBay,...

Hi eslapion, Very detailed analysis of different PLA solutions. The screen shots tell a very persuasive story that even I can see. :) It is very clear from the screen captures that your Original ST 27C512-90B6 OTP PROM is better at handling a voltage drop than the Commodore Factory PLA! It is a some...

Hi eslapion,

Thanks.

Hi eslapion, As such, you should never replace 74LS series of chips with 74HC because these have a logic threshold of Vcc/2 (they work from 2V up to 6V) so when powered with 5V, the logic threshold jumps to 2.5V while 74LS chips are only guaranteed to signal up to 2.4V creating potential incompatibi...

Hi eslapion, You are right an oscilloscope seems the next step on for me. I have seen some Hantek oscilloscopes that attach to PC. Presumably it shares the screen for viewing. I did look/am still looking on eBay for those osciloscopes you originally posted the digital Tektronix TDS210, TDS 1002 or T...

Hi MCes Thank you very much for sharing your thoughts on this matter..... Apologies for not replying earlier. The time difference being what it is and taking in all this information and processing it. I am not a very smart person. It is good to debate worthwhile topics such as this. :D Here is what ...