Denial

What is the ! for in !ROMH & !ROML? They can also be called /ROML and /ROMH and the prefix, whether it's ! or / means this signal is active when low or logically true when low. Sometimes this is also noted with a horizontal bar above the designation. You see that often in the datasheets for RAM...

Yes, these Winbond branded chips are in my opinion non genuine knockoffs from who knows where... Then I go back to my previous suggestion: Check the AT27C512R from Microchip, the AT27LV512A also from Microchip and the AT49F512 Flash ROM. All 3 are available at Digikey and all are from official sour...

I have a few Behr-Bonz for sale but unlike those of SnakeGrunger, mine don't come with a case.

Could this be why some think that the Winbond W27C512 EEPROM is a possible substitute PLA? I noted a few forums where there was/is a great deal of discussion about using this Dodgy Winbond EEPROM 27C512 as PLA substitute. To answer that question implies you can assume Considering that I can observe...

@banman
You're studying this board in particular because it happens to work fine with a PLA substitute which is truly borderline and the glitch you noted clearly indicates this is not something you should use.

I'm wondering exactly what you're looking for.

I think I figured out where R42 is positioned. I just can't figure out where & C204... ... Here's a picture of the board. Do you have any ideas where to look? According to the schematics, the presence/absence of C203 and C204 depend on the type of PLA installed as in 1983, Commodore had the old...

If I am reading this correctly, would it be fair to say that different revisions of C64 mainboard PCB's have different physical layouts which may in turn have different impedance loads? It doesn't vary much but the answer is yes. However, keep in mind that traces for digital signals on various C64 ...

Got some 90b6's coming from Ray Carlsen. This is mainly to check what it does right that others do wrong. That's something I can easily explain to you. All memory chips will generate glitches when used as a logic IC. The PLA of the C64 is a 16 inputs, 8 outputs combinational logic device whose func...

comparing the outupts to a genuine pla , timings , glitches , everything i can to see the difference between the good and the bad. The M27C512-90B6 is 'good enough' but it shouldn't be considered a reference. It works well on boards 250425, 250466 and later revisions of the 250407 because they have...

First to test roms against an original PLA ... Would you care to explain what you have in mind ? When I created PLAnkton, I examined the behavior of early C64 PLAs that were provided with boards 326298 since those truly work with everything. I didn't 'test them against' anything. I adjusted the lat...

I will have to get hold of him. Just wanted to include it as it is the one that started the thread. The point of the thread is that in 2008, I discovered the M27C512-90B6 as one of the very few (E)PROMs which could safely be used that could be used as PLA and a group of people did everything they c...

Don't worry , i think i will leave it . I was just giving you a chance to sell a few. If I sell you the blank EPROMs, I have no idea how you're going to use them and the exercice could turn into hundreds of exchanges about doing this or that to get it to work. I'd rather you have a working solution...

two resistors and a tansistor will make an inverter just need the eproms to go with it , how much for six and uk postage? PM might be better. You absolutely can't check how fast your inverter will act when you use 2 resistors and a transistor. Both EPROMs may end up signaling at the same time and t...

eslapion do you have any 90b6's left? i would like to purchase one to use for comparison with a PLA the same as the rest. I have 2 left and I keep them preciously. On the other hand, I have a pile of M27C256B-90B6 and you can combine 2 of them in piggyback along with a 74HCT14 inverter to get the s...

Would anyone be interested in a Behr-Bonz Trainer cart ?