Let's upgrade an early Socket 7 board beyond the limit (Part 2): VRM, MMX, Testing

hello and welcome in my last video i showed  a painting mainboard from the pre-mmx times   which i wanted to upgrade to a painting mmx  this main board doesn't support dual voltage   required by a pentium mmx out of the box so i  decided to design a voltage regulator module   which would make it possible to use that cpu  on that main board if you didn't see that   last part i suggest to watch that one  first and then come back to this video   first of all a small remark about the explanation  of a switching voltage regulator which i made in   the last part unfortunately it was not right  about one detail i said that the transistor   cools down when it is off and warms up when it is  on however the transistor actually warms up only   in the moment of switching and as soon as it is  completely on or off it can cool down again the   explanation for that would be a bit too much  for this video that's why i made that shortcut   in the last part which obviously was wrong and  was instantly spotted by many mindful viewers   and i would really like to thank you all for  the corrections so where did i stop oh yes i   want you to test the pentium mmx200 cpu in this  main board for the first time so let's do it and that's it thank you for watching   just kidding as you probably heard there was a  post beep which doesn't actually sound too good   it's kind of choppy but at least the cpu doesn't  get too hot and the vrm didn't explode that's a   good sign i guess i mean exploding vrm  is usually a bad sign don't you think okay i will need a second hand  to make some measurements so   let's mount a cpu cooler a  graphics card and a pulsed analyzer let's give it another try at least some numbers  are running on the post analyzer so the whole   thing is not dead um oh and i already see an image  on the display but let me check the voltage first   yeah almost 2.8 volts and stable very good and here is the display as you see we have an  image the cursor is blinking so it doesn't totally   hang but it also doesn't continue so far what's  odd is the detected cpu a pentium 180 megahertz   that is definitely wrong but maybe we can  change it using a newer bios version and   where can we get the latest bios exactly  the ultimate retro project former known   under the name uh-19 it has recently moved to a  new domain ultimateretro.net and got a lot of new   and exciting improvements since i introduced it  last time this is the best place on the internet   if you are searching for images documentation  bios dumps and more for the retro main boards   let's search for the p slash i-p-55 here  is the list of matches and we need the xeg   version here we go the images the documentation  and here is the latest bios from 1997. perfect by   the way if you have a main board which is not yet  in the database or which misses pictures bios doms   or something else please consider to contribute  all the data you can provide to this project   it is made by the community for the community  and some really nice guys are working hard   in their spare time to make it even better so they  need all the support they can get and i wrote the   bios using my tl866 ii plus already let's replace  the old one and see if something changes by the   way i always try to use another p-roms and keep  the original untouched at least as long as i'm   not sure that the newer bios works as it should  afterwards i still can override the original piro   so let's see if it helped oh the post beep does  already sound better and is not as choppy anymore   and would you look at that the new bios helped  indeed and there is penthume mmx message laughing   at us from the display however the 166 megahertz  clock is not right the jumpers are actually set   to fsb of 66 megahertz and multiplier of three  so the overall speed should be 200 megahertz   so i tested off camera a little bit and  it turned out that it makes no difference   how i set the jumpers for the multiplier  the cpu always remains at two and a half   and 166 megahertz however the frontside  bus seems to be right at 66 megahertz   let's try the pentium 133 once again and  see if the multiplier jumpers work at all   this cpu needs single 3.3 volt voltage so i have  to remove the vrm and here is the first good news   this modification is completely revertable  all i have to do is to remove the module and   put the jumpers across the pins as they were set  originally and as i showed it in the last video   so now the cpu should run again normally at  3.3 volts just as before so both multiplied   jumpers are currently on set and due to  this table here we should get a multiplier   of 1.5 with a frontside bus of 66 megahertz we  should now see 100 megahertz pentium detected and here we go 100 megahertz  indeed so let's set the jumpers to   open closed which should mean two times 66  megahertz or 133 megahertz core frequency and we are getting 133 megahertz indeed  so the jumpers are absolutely okay but   why don't they work with the pentium mmx well  after some investigation i found following first   of all a well-known fact that the pentium cpu has  two pins bf0 and bf1 which are used to configure   the core clock these pins can be set either to 0  or 1 and so different front side bus multipliers   can be configured so far so good but here is what  i found in the intel paint you motherboard design   guidelines on the painting processor the bf1 and  bf0 pins have internal pull up resistors but on   the pentium processor with mmx technology the bf1  pin has an internal pull up resistor and the bf0   pin has an internal pull down resistor the jumpers  are pulling the bf0 and bf1 pins low and that   works only on the non-mmx pentium cpus because  they have internal pull ups on both pins and   since the pentium with mmx has an internal pull  down on the bf0 it is already always low no matter   how i set the jumpers so all i have to do is to  add an external pull up resistor on the bf0 pin   to be able to set it to high if needed apparently  the documentation also says that the value of the   external pull up resistors used on the bf0  and bf1 pins should be 2.2 kilo ohm or less okay let's put back the vrm module   the cpu is already in place let's set the jumper  to the multiplier 3 and let's give it another try   and we have a 200 megahertz pentium mmx a cpu  which was released a year after this main board   shows some signs of life in it let's put back  the cooler and i will also insert this compact   flash to ide adapter with a card where i have  ms-dos pre-installed with some tools and games and we are in dos let's start something   for example doom to see if it is  able to finalize the benchmark at all meanwhile let's test the voltage the   voltage regulator is barely warm  now but it didn't run too long yet the voltage is set to 2.8 volts and we are getting  about 2.77 volts that's good enough but meanwhile   i recalculated the resistor values and the next  revision of the regulator should deliver even   better values anyway 2.77 volts is absolutely  within this pack so nothing to worry about   and we got about 1 000 real ticks however the  performance values are unimportant now all i   currently hope to see is some kind of stability  the species detects pentium mmx200 as well   and the memory throughput test  uses the mmx instructions too i started now pc player benchmark which  i'm going to let running for a little while   let's see how stable it can work  over a longer period of time this linear voltage regulator is usually  used to power the cpu and it gets very warm   and often fails because of that however since we  have now a dedicated vrm for the cpu core voltage   this on-board regulator is only used for the  i o voltage and therefore remains stone cold   currently it is around the room temperature about  19 degrees celsius what i would also like to test   is the output ripple it is important to  have it as low as possible for a stable work   and as you see the ripple is about 50 millivolts  not super good for 2.8 volts but also not bad   i think painting mmx is designed to stand up to  100 millivolts so 50 millivolts is an acceptable   value my oscilloscope seems not to be able  to catch the frequency exactly but it seems   to jump around 150 kilohertz which absolutely  corresponds to the fixed frequency of the dc   dc converters which i'm using here let's leave the  system running a little bit and see how it behaves so about one hour passed the pc player benchmark  is still looping on the screen nothing bad   happened so far let's see how hot the regulator  is yeah almost 50 degrees celsius although   absolutely in limits still it is quite hard  to be honest the cpu seems to be cooler and   it blows the air directly onto the voltage  regulator so it gets cooled by the fan as well   but still i think this was a successful  first run i would say the whole thing   didn't explode it is not too hot the voltage  is okay the ripple is also within limits   and yeah the pc player benchmark runs  also since an hour without any issues   so the pentium mmx 200 megahertz is running with  66mhz bus and multiplier 3 cool and stable sole   farm this is already a huge upgrade over the 133  megahertz pentium which was in this board before   and the mmx is even beyond the original specs  of this main board but the question is how far   can we get can we push the limits of this board  even further of course we can initial idea of   this project was to get the voltage below 3 volts  so this main board will be able to run with cpus   other than the non-mmx pentium versions and  this seems to work so far however the voltage   regulator can provide voltages down to 2.2 volts  and which cpus do run with such voltage i am   happy to present to you an amd k62 i have this  cpu in different frequencies and this one is a   366 megahertz but the speed doesn't matter now  interesting detail is that this cpu runs with   2.2 volts the k62 cpus were specified to run  with up to 100 megahertz frontside bus but our   board can only 66 megahertz so let's start low  and see what happens if we just switch the intel   pentium mmx200 by this amd k62 the multiplier  jumpers will remain at 3 and i just have to set   the switches on the voltage regulator to 2.2  volts this is when all three switches are on   everything else will remain in the same  as it was with the pentium mx200 before and would you look at that the cpu starts at 200  megahertz it says amd k6 and not k62 but that   doesn't matter the bios just doesn't know the cpu  id because it is simply too new let's check the   voltage first yeah we are at around 2.2 volts and  that is fine and we can continue the test as you   see in dos the software detects the cpu correctly  even if the buyers didn't know that it is actually   an amd k62 the cpu id tool says that it is an  amd k62 running at 200 megahertz a multiplier 3   and 66 megahertz front side bus everything  is right let's see what speed says tells us   yeah and also here we see k6 to 200 megahertz it  even reports active 3dnr feature the benchmark   values don't mean a thing now since i didn't tweak  anything in bios whatsoever this is something what   we can check out later let's run some pc player  benchmark and test the vrm temperature so far so after about 10 minutes of pc player benchmark  we have 47 degrees celsius this is not nearly a   critical value i still can easily touch the  regulator okay let's take a look at the k62   datasheet in particular at these three pins pf0  bf1 and bf2 now compare this pin out to the one   from the intel pentium where we see bf0 and bf1  but instead of bf2 there is an unconnected pin   well as you probably remember those bf0 and bf1  pins were used on the pentium cpu to select the   multiplier and the bfz european is the one where  i soldered the pull up resistor previously to   make it work within intel pentium mmx so amd  k62 has obviously three of those pins vf0 bf1   and bf2 you see k62 was primarily made  for the super socket 7 main boards   which usually were prepared for much wider cpu  clock ranges so two pins were simply not enough   to control the multiplier up to six so compared  to the original intel pentium amd introduced the   third bf2 pin in addition to the ones which  were used on the intel pentium previously   and in this table you see the three bits  which represent the bf0 bf1 and bf2 pins   on the cpu in little indian manner so the  most tried bit is bf0 and the most left is bf2   the cpu pins bf0 bf1 and bf2 on the cpu were  connected to the three jumpers on the later   socket 7 main boards and so the user could  configure the multiplier unlike on our asus   mainboard here which due to its age knew only the  bf0 and bf1 there was simply no jumper for the bf2   to remain compatible amd equipped the bf2 pin  internally with a pull up resistor so on main   board which have no ability or no jumper to set  the bf2p into low this pin was always pulled high   so looking at this table we have to concentrate  on the first four entries where the first bit bf2   is set to high or is one with other words other  setting would be only available if we would modify   the main board and add an additional jumper to  the bf2 pin on the cpu i'd prefer not to do it   now that's why let's ignore all multipliers  in the second half of this table for now we already know the multiply 2.5 which would set  the cpu clock at 166 megahertz and 3 which would   set it to 200 megahertz this is what currently the  jumpers are set to 0 1 by the way 0 means jumper   is set and one means jumper is not set let's take  a look at the next possibility the multiplier   3.5 it expects bits 1 1 so both jumpers are not  set let's remove the jumpers and give it a try and as you see the board reports amd k6 233 means  66 megahertz front side bus and multiplier 3.5   that is correct even if the k6 is actually a k62  but i explained already why it is shown wrong here and again in the cpu id tool we see k62 at 233  megahertz detected with the multiplier 3.5 and   the front side bars unchanged at 66 megahertz and  let's play the same game here again i'll fire up   the pc player benchmark to put some load onto the  cpu and test the temperatures after some minutes and again about 15 minutes passed and we have 55  degrees celsius an absolutely acceptable value   the vrm feels very warm but is far from  burning and the onboard linear regulator   for the 3.3 io voltage is still stone cold so  there is no stress on it at all very very nice let's go back to the mdk 6 data sheet once again  i promised to go beyond the limits of that asus   mainboard and i would say we already stroked that  aim however we can do even much better take a look   at this entry for the multiplier 2 the datasheet  says here that two or six with a remark down here   the ratio selected is dependent on the stepping of  the model eight the two times ratio is supported   on the model 8 7 to 0 whereas the 6 ratio is  supported on the model 8 f through 8. well   the model 8 refers to all versions of the amd k62  but as far as i believe the 7 through 8 stepping   versions were the cpus with the id 26050 and due  to the datasheet they supported the multiplier of   2 but the versions with the id 26351 which i have  belonged to the f through 8 stepping and supported   a multiplier of 6 instead of 2. so what we  have to do is to set up the multiplier of two   on the board and the cpu should actually run with  a multiplier of six let's first set the jumper but that was not everything what we have to think  about the multiplier of 6 and 66 megahertz front   side bars would mean that the cpu would run at 400  megahertz and with rising frequency the cpu gets   a lot more power hungry take a look at this  table the amd k62 which i have will draw up   to 11.25 amps at 400 megahertz and that is a real  bummer since i designed this vrm initially for the   pentium mmx and not for such a cpu which would run  at 400 megahertz with this design the regulator is   specified for up to 6 amps only and 11.25 amps  would be almost twice as much as it can deliver   but who would i be if i wouldn't try it though  i built multiple of these modules and i think   that i can sacrifice one for the signs however i  expect it to get very hot and i have to make some   preparations i have here some small heatsinks  which hopefully can cool down the ics on the   module a little bit so i glued a pair of  that heatsinks already on one of the modules   i already tested this module behind the scene  with 2.8 volts and it works flawlessly what i   need to do is set it to 2.2 volts again  this is where all three switches are on   so the second thing is an additional cooler  which will blow over the regulator i will   connect it to the 12 volt fan header of  the cpu so the cpu fan will not work now   but i hope that this bigger fan will be  strong enough to keep the voltage regulator   and the cpu cool for some time at this point i  would really like to make an important disclaimer   not only about this project but about everything  i do on this channel because in the last time i   read more often that people assume that i'm an  expert in electronics that is absolutely not   the case and can be even a dangerous assumption i  am quite an experienced software developer but i   am in no way an experienced hardware developer all  you see on my channel the diy projects the repairs   everything is just my hobby i had a lot of  theoretical electronics in the university   many years ago but only as much as  a computer scientist needs to know i   never collected any practical hardware development  experience in my job and all you see me doing here   is a result of my self-development i just like to  learn new things and as everybody who is learning   i also do a lot of mistakes i always try to  do my best but sometimes i go the wrong way   i think it's normal and i try to understand and to  explain many things as simple as possible because   i think that simplification is the key  for the solution of complicated problems   but i also tend to oversimplify things sometimes  and drop too many details so always take it with   a grain of salt and please never see this  channel as a tutorial i'm just glad to be   able to share my hobby with you and i always hope  for a nice experience exchange in the comments so everything is ready let's see if it explodes   okay we have a pulse signal and on the screen  we see amd k6300 that is definitely not right   but again maybe only because the bios is  now extremely confused and here we see 375   megahertz which is again not what i was expecting  to see but let's continue nothing exploded so far   i think that i don't have a lot of time but  the cpu id tool clearly reports an amd k62   400 megahertz with a 66 megahertz front  side bus and a multiplier of six on this   board which was specified for a non-mmx cpus  with up to 200 megahertz only this is amazing   let's see what speed c says also here amd k6  400 and down here look at that we are almost   at the performance of a pentium 2 400 okay now i  go with all in and start the pc player benchmark   let's let it run and test the  temperature of the voltage regulator 72.8 degrees celsius that is quite hot  already if you consider that it was cooled   directly by a strong fan okay  it is very hard to touch as well and as you see the benchmark is still running i  am really surprised and a little bit disappointed   that nothing exploded but i think i'll stop  the experiment now because i would like   that this system survives since i have further  plans with it okay first important note is that   as i started to work on this project my main aim  was to get the pentium mmx200 running on that   main board and i would say that i reached their  target however pentium mmx pulls only up to 5.7   amps and i designed the voltage regulator for that  current in the beginning i unfortunately didn't   think that i also could try to run a k62 cpu on  this mainboard i thought about that first as i   was searching for the bios update which would be  able to recognize the pentium mmx and as you saw   it would work theoretically shooting the system  performance to the moon but the voltage regulator   was just not made to handle up to 11 amps and so  i currently can't go that far with this revision   second possible issue with this design is actually  due to my lack of experience i used 2 switching   regulators each specified for up to 3 amps to be  able to handle up to 6 amps in total my concern   was from the beginning that trying to control the  same output from two regulators could end up in a   fight between the regulators and although i didn't  encounter any issues during my tests i still have   a bad feeling about it and some viewers have the  same opinion in the comments to the last video   so i think that i have to do something about it  as well as you see this revision 0.1 is the very   first one and fortunately i already designed the  next one which should be able to stand the current   of up to 15 amps and do everything with one dc  dc controller and a beefy mosfet but that one   currently exists only on paper and i'm going to  order the new pcbs and parts in the next days   so i am glad to announce that there will be  another video to this topic in the near future   where i hopefully will get as much out of this  system as i can i'm also going to upgrade the   cache and run a lot of benchmarks so if  you are curious don't forget to subscribe   there were also some questions in the comments to  the last part if i am going to open source this   project and the answer is yes just as always  i open source all of my projects and this one   will be not an exclusion however i decided to not  open it yet since i would like to provide you guys   the better revision first which hopefully will  also work for the higher current so please stay   patient a little bit longer and hopefully in the  end i can provide something what is even better   as i already said i really like to learn new  things and for me every day where i didn't   learn anything is a wasted day so if you have some  good information source where i can read and learn   something about one particular topic please  consider to share it with me otherwise i just   hope you enjoyed this video and would be glad to  have you on my channel again thank you and goodbye

Channel: Necroware

Views: 84,056

Keywords: retro, hardware, soldering, repair, review, nerd

Id: J0NLGfocviU

Length: 30min 34sec (1834 seconds)

Published: Sat Nov 27 2021

Reddit Comments

[u/TT_207]

Watch the prior video as well on making the VRM. Found this genuinely really interesting and something I'd love to try if one of my piles of old motherboards has the right blank headers!

While the cpu isn't overclocked and the bus is still 66MHz getting the board to go well beyond the limits it was supposed to on processor frequency power and voltage spec was quite interesting.