#10 'The PLAin Truth About the Commodore 64 PLA' at World of Commodore 2017

you the world of Commodore the world of Commodore show was a rather large annual event that took place in my neck of the woods through the 80s and early 90s and even today the world of Commodore event continues thanks to a very vibrant retro computer community and the dedicated efforts of tee pug the Toronto pet users group on December 9th 2017 I attended the world Commodore 2017 gone are the days of large convention center Expos drawing thousands of people and hundreds of vendors as bacon as exciting as those shows were back in the day I do enjoyed a contemporary distilled version of the world of Commodore where there's still lots of exciting things to see and hear [Music] whoa whoa hold on this is fun and cool stuff it really is but for me what I most enjoy these little pompadour events are the presentations and this year there's somebody very interesting I want to hear speak francois de la fayette better known as s lap young or a slap yen in my lazy english pronunciation who is the developer of the plankton a Commodore 64 PLA replacement okay so a little backstory here about six months ago I had a Commodore 64 on the bench that needed a new PLA but I didn't have any spares at the time so I started looking more deeply into alternative replacements and yes I know all the pigs Kaleigh replacement players were already on the scene with their designs but inspired once again by gadget UK's videos I decided I wanted to make my own DIY PLA replacement using a specific one-time programmable prom just like he did and I would try my hand at making my own pin out adapter PCB to work with that specific prom for starters I came up with this small footprint to layer PCB design basically just an adapter to convert the pin out of the 80/20 7c 512 r IC to the standard Commodore 64 PLA soccer now of course having delusions of grandeur I named my little PCB replacement 64 see what I did there of course I ordered some prototype PCBs as well as some of the very specific Atmel 45 nano second proms and all that was left to do was assemble and test my little replacement 64 project board looked pretty inserted into my Commodore 64 test machine but what at work the first test was with the Commodore 64 Brad been with an early revision motherboard and everything appeared to work fine but when I started to test later revision boards it was a different story this is a c64 breadbin with a later revision 2 5 0 4 to 5 motherboard and it does not like this DIY PLA replacement ladies and gentlemen I present to you the coup forg 66 after some more tinkering and testing I really wasn't happy with the results I was getting and to be honest I was getting a little discouraged so we ended up shelving this project fast forward 4 months and I find myself at the world of Commodore 2017 waiting for none other than the creator of plankton Commodore 64 PLA replacement to speak I hope to learn more about the PLA in general shedding some light on my difficulties and to learn which alternatives work and don't work what follows is Francois love A's presentation the plain truth about the Commodore 64 PLA at the world of Commodore 2017 the presentation runs about 28 minutes and it does get a little technical at parts but if you're a retro computing fan and in particular like to repair Commodore 64's I'm sure you'll find it very interesting just decided and please remember all the pains expressed in this presentation are that of the presenter not of me or of this channel enjoy you is used in the Commodore 64 is equivalent to a programmable logic array 24 l8 that is it has 24 I Oh s actually 16 are inputs 8 and power outputs it was used in pet computers to complement 74 LS logic I sees just like in the 64 its function is to integrate to prevent having a mass of discrete logic I sees the consumer lot of power it was not used in the Bitcoin which is apart from the presence of a color video chip is actually a much simpler computer than later generations of computers as far as I can tell the original Commodore 64 PLA was a programmed 82 s100 but the Commodore 64 of course became very successful computers and it was produced in millions of unit so Commodore to save money decided to make their in-house version of the chip some of the generations were called the 7700 0 1 later generations would be called 8700 0 1 and person that was the most person that I know who knows the most about the transition from using a chip made by an external company to making to come to our making their own model is Thomas diesel aka scope is that a familiar name he published a very important document called the PLA dissector now whether you have an 82 s 100 in your hand or Commodores on version both consume approximately 100 million on the 5 volt so that gives a total heat dissipation of 500 million watt half a watt such a small surface no cartridge is attached to the 64 what you will get is not 5 volt it's going to be lower than that it's going to be between three and a half and four volts and that's considered to be your logic a logic 1 the input thresholds of the PLA is also levels and that means anything above 1.3 volt is considered a logic one and anything below is considered a logic zero the response speed of the PLA is much lower than 74 LS chips up to 3 times slower so even though he consumes a lot of power it's not very fast the PLA uses only combinatorial logic which means that for every single specific input it will always get the same result there is no registered logic see filter added to the cast ramp output which is an 18 on the ple - all these boards otherwise access to the RAM would be problematic this information also comes from Thomas diesel when Commodore decided to make their in-house version of the PLA they made some error in the chemistry use and this causes the chip to essentially self-destruct from the it's up from the inside as I said before this is a chip that makes half of what of heat so if you leave a Commodore 64 running especially older ones running all day long on a very hot summer day very often PLA will fail since the PLA is essentially a 24 l 8 programmable array is it has more programmable equations than a 2012 10 which is a standard chip but you can't combine two bowels and yes it will and a real PLA sold by Thomas easel does precisely that is it possible to use modern programmable logic it's possible with many conditions because among modern programmable logic I sees there are very few which still operate at 5 volts but it also happens that if you have something with with 16 inputs and eight outputs that always provides the same result given a specific input well it's it's the same as a memory chip but memory chip are not designed to be used as logic chips and most will cause garbage on transitions with a very few a second there is one exception that I know for sure and it's this chip which I've been talking about for years on various farms and this chip can do this because it has a very slow output transition rate a very low school rate the m27 c5 12-9 t b6 is usable as an ordinary prom an ordinary memory chip you can use it to install g feed us and your 1571 or your 1581 but it works perfectly as a ple substitute and in 2008 I was still at university in studying Electrical Engineering and we had access to enormous that chronics logic analyzers that had 32 inputs and they were running Windows 95 which you couldn't change by the way it was a special version of Windows 95 and 7 there and they had a sampling rate of up to 1 Giga sampled per second and I brought my Commodore 64 at school and I installed this chip with the proper adapter and tested it how it reacted and I was amazed to see that there was an 11th analyzer there were no glitches at all and I couldn't not figure out why until I analyzed these signals with an oscilloscope and I realised that when the up was changed from 0 to 1 or 1 to 0 the transition was very very slow so if the logic system inside the chip was to generate any glitches you were essentially filtered out this chip when used as a ple consume eight watts of power it's 8% doesn't produce any heat at all and reduces the power consumption of your Commodore 64 by 92 milliamps it reduces load and your power supplied by approximately 10% so not only do you have a Commodore 64 which eats less it reduces you reduce the chance of damaging your power supply but of course these big special machines they were in the classroom and it was not possible to bring outside the classroom any of the tetris these were not fitted with USB bows or anything that could have allowed me to bring the results of my research outside except perhaps if I had had a very good camera to capture to photograph the screen but as soon as I began talking about this potential solution in various forums especially on Lemmon 6 before I was immediately immediately targeted by a special character was laying his grow pads and he posted that this chip was was generating bus contentions and I didn't understand what he meant by that but what he meant by that is that the PLA in the Commodore 64 is essentially a traffic cop managing an 8 we cross it there are eight outputs to the PLA and each output signifies this has access to the bus this has access to the bus by 2011 SD discontinued this chip so you couldn't buy it anymore when it was available I remember buying more than 100 of them for for a dollar not only was it discontinued by Asti but it seems that knowing that it could be used as a ple cause the demand for the chip and if you go on eBay and try to buy an M 27 c5 1290 b6 what you'll have is a fate and the original is easily recognized because the ink on it has a very low contrast and the pin 1 notch has a very special shape these fake are actually win bond problems that have been rebranded according to this three-letter code here this Jim this chip would have been made in Malaysia as he never made any of these chips and the leaves go so you can't get it any more and if you try to get it on eBay well you get a bad surprise if you have an EEPROM used as a pili in the Commodore 64 and you have busk intentions this is not good from the logic analyzer and it was actually done by people in Germany you see multiple outputs going load everything in the Commodore 64 around the rum signaling is active low which means if you if you get a zero it means it's okay to output and you see that you have multiple zeros here and the worst is here this is essentially a PLA telling everyone can talk so this is what we call the busting and this is what you get if you use just about any standard EEPROM of the 27 27 C 512 family and tried to use it as a PLA in a 64 now I know of two ways of detecting glitches or bus contentions generated by whatever problematic PLA you can use a logic analyzer like on the previous picture you can use this small circuit connected to the cartridge port if you don't have any cartridge in the cartridge port after the Commodore 64 has powered up when you power up to 64 it will check if there's a cartridge plugged in but once that's done these two lines should never go low as simple as that and if they do it will turn on the LED connected here and this resets this LED so if you have this connected in the cartridge port when you power up the 64 Yeley you will turn on because the 6510 is checking for the presence of the cartridge at which point you press the button if this LED ever turns itself back on you have a problematic appealing as simple as that the other way that I know which is much less than technical but requires having something a little bit special is the Super's exon game cartridge and not the dis version the cartridge uses a flip-flop to toggle access between the upper and lower half of a 16 kilobyte from the card inside the cartridge is actually 20 kilobytes of code which is something in 140 ROM and 1/16 kiram and because the flip-flop is tied to Roman age isn't in research there's any glitch on ROM age the cartridge will just start displaying garbage or use the m27 c5 1290 b6 even though it was essentially a $1 replacement ple that everyone just had access to it managed to this brush because in the end of the 100 chips I bought I managed to sell 75 and in the end last year the 25 last ones that I had I traded to Rey Carlson in exchange for that commodore 64c nowadays thank a mouse software on their website is suggesting that it's a good idea to build your own little board here and put on it and at mill 27c 512 4550 you and use it as a ple replacement but group as is insane and me and a lot of other people have tested the Adnan problem and it generates massive glitches and bus contentions but drop ass isn't saying anything because Pro pass is the friend of Jen's Cantrell and Jen's compelled wants to sell you a super ple and what happens when you build this and try to use this as a PLA a lot of cartridges don't work anymore and initially a lot of people will think their cartridge port has a problem but the problem is with the PLA and when people get tired of this because there we are they realize there are more subtle problems which I will show you then they want a good good thing this is per ple but the super PLA has problems if you want to use a modern logic I see as a ple substitute here are the requirements it must be Indian level compatible fun impose which means if it receives a signal higher than one point two people it must be considered or one not two CMOS level CMOS level is anything about two point five it's not the same it must have a small hysteresis on inputs otherwise fast load in any other cartridge that used the same tiny trick it will fail this vastly uses a large capacitor as a form of tightening trick but it's not the only cartridge to use that trick it must respect cache Ram timing constraints cache Ram is a line which is central to DRAM access and it's because these timing constraints are not perfectly met that boards for mo seven for twenty-five and 466 have the extra RC filter which I mentioned earlier these are our 42 and C 204 they don't exist in the original Commodore 64 only exists on later BOTS preferably it won't generate heat and preferably it will not be oversized and cause physical conflicts but surrounding components there's a new modern requirement if you are to make and sell PLA substitutes on the market now your component components all the components you use must be grow as compliant reduction of hazardous substance yes because that also obliges solder - sorry them to the board if you just saw the product everything must be ro is compliant no let no Kenya here's a list of a few products which use modern logic ICS PLA this is real ple this is actually a new version of real PLA because the older one used a pair of did this version uses surface mount components and as such it still is slightly oversized but much less than the previous version it uses two different logic chips to meet in order to be able to replicate all the equations the logic equations in the Commodore 64 PLA and the super PLA uses the old Mac 210 do does anybody in here have a cypher graphic 64 for the Amiga you do the cypher graphics has two of these chips on so these chips you see - twelve here that doesn't mean it's 112 it's rated for a hundred and twenty nanosecond it's rated for twelve and a second it's a very very fast cheap and it runs out of five volts the super PLA v3 as you can see is oversized so it causes a physical conflict on some of the motherboards it's I don't think it's usable it's x64 but I could be wrong and the Mac 210 well that's an old chip it was discontinued I think about around 1999 or 1998 you can't buy this anymore and it's not robust compliant it's led in there plankton uses the modern xc90 536 Excel this is a plantain this is an older version of the board the ones I have here is a newer generation it eats all requirements but it has something that some people may think is undesirable it runs at low voltage now a lot of people think this may be a problem because they assume that since all the chips in the Commodore 64 are powered at five Alton that they also signal at five volt which as I said earlier is not the case in our original Commodore 64's every integrated circuit is designed to communicate with TTL levels in mind and this means that anything above two volt is considered a logic one so in theory I could run plankton at three or 3.3 volts but I choose to run it at 3.7 and I'll tell you later why and for the most of the other solutions I have seen including the older xc90 536 not Excel don't meet the timing constraint for Katherine and actually it's something rather amusing if you go on eBay there is this gentleman called Admiral Decker and he sells a ple substitute but he sells his pla substitute with a resistor in the capacitor and he tells he's telling you if you have this and that and this and that board you have to add these components solder them yourself actually is telling you to do what Commodore engineers did with boards 407 and 425 and 466 that is to at an RC filter manual of course you have to have a certain safety margin so he usually manufacturers TTL chips will guarantee you that the signalling of one is done at two point seven volt or above and signaling at zero is done at 0.5 volt or below and you can see something similar here on 5 volts Simo CMOS chips they signal a 1 close to 5 volt they signal a 0 close to zero volt but anything above 3 point 5 volt is considered a 1 anything below 1.5 volt is considered a zero and you can see here this causes a passion potential conflict well what are the next step recently I exchanged Fredrik growls if I'm from who designed the PCB and the VHDL code for plankton and we decided to turn the joke in a bit on mr. donfield we know of the problem with fast though and the problem of the cast iron timing of the super PLA so we offer you a slap which is a super PLA festal fixer it's a little daughter board that you can put under the super PLA and it will do two things it will provide hysteresis on input because the mac 210 doesn't have this theory mr. this and that what's that's what makes it them incompatible with that slope it will provide hysteresis on the input lines coming from the cartridge point and it would it will add the necessary delay on the castrum output making the super PLA III as good as plankton except it doesn't consume as little power is plankton and the other new development is mega plankton its replacement feeling for the short board which has a much larger killing because come what are integrated a bunch of blue logic into the PLA that is inside that computer just crash until it goes game over but you see the scrolling there's nothing wrong with it the colors are ok no problem in particular this is an ordinary EEPROM me used as a PLA substitute and as you can see I started the 64 all the startup message okay there's no error there's no color problem nothing that could make you suspect there is any problem okay but you can't see the problem but that is until you try super zaxxon with it at this point you don't see anything wrong okay you thought it was good and this is actually what a tiny mouse software is encouraging you to do you think it works but today you use a cartridge you've got a problem there are ninjas but I don't know them by heart I know it's a problem also with the 1541 ultimate families of cartridge but what I'm going to show you now is st's from that I talked about and grope as told you not to buy because it was going to cause a nuclear explosion on dollar u.s. we go to the basic first looks fine just like the other EEPROM $1 PLA replacement for you so my point is everybody could have had a PLA substitute for a dollar just because one man in particular is a very good communicator and didn't want people to use this convinced everyone to steer clear of it the only person I have to here but I want to keep them the only other person that I know it has the real thing in stock not the fake ones on eBay is very Carlson so my point is plankton and it works real well it does as good a job but I would have preferred not to have to because I don't sell plankton to make money I sell it because I know it pisses a person and I was fortunate to have a bit of one-on-one time with a slap you I told him about my prom experiments and showed him my little EEPROM the PLA socket adapter board I was subsequently schooled by his level giving me more first-hand demonstration showing me why the prom solution might be a decent temporary replacement workaround but only a native PLA genuine 90 v6 variant of the esti problem that he mentions in the video or even plankton itself which is 99.9% compatible with all c64 board revisions are really the best PLA replacement choices of this time Francois is definitely a passionate guy and is exceedingly knowledgeable about the c64 PLA I'm happy to have had the opportunity to meet him if you want to learn more about world of Commodore 2017 I highly recommend that you read Greg Mizzou's detailed blog review of the event over at c64 OS comm I'll post a link in the description Greg is created and maintains c64 OS comm which has become an excellent contemporary resource for all things c64 OS and hardware related I do recommend that you bookmark c64 OS com you won't be sorry okay next topic donations I realize that my retrocomputing channel is still pretty young and I don't have a patreon account at this time but I have introduced a PayPal donation link in the descriptions of all my videos so if you find that you enjoyed a particular video and you would like to support my Commodore computer rescue and repair efforts please consider a small donation to the channel finally I'd like to thank a few people Rayman Negron space boy G Greg Nasu and gadget UK for permitting me to use their photos and videos in the making of this video also a long overdue thanks to mermaid for allowing me to use cursive music that you hear in all my videos and that's it for now as always thanks for watching thanks for your time and I'll see you again soon [Music] [Music]

Channel: MindFlareRetro

Views: 34,946

Keywords: commodore, c64, c-64, commodore 64, computer repair, retro computing, retro computer, retro computer repair, retro gaming, mindflare, mindflareretro, mindflare retro, sid, vic, pla, PLAnkton, eslapion, Francois Leveille, World of Commodore, WoC, U17 PLAnkton, Fredric Blåholtz, e5frog

Id: ofg33zk9uCA

Length: 36min 12sec (2172 seconds)

Published: Sat Feb 03 2018