486 Socket Blaster, Adding 3.45v support to the supposedly unupgradable IBM PS/1 

Part 1: Repair of PSU and CPU. here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-49ZOxgc2pXI.html Part 2: Hacking the MOBO: here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-kxbkkpe6wfM.html Part 3, This video! Support me on patreon.com/Epictronics

The creator of this has a youtube channel and did a video on its creation. "ScrapComputing"

Very happy to see scrap computings socket blaster getting some love.

I think I know how to set the clock multiplier to 4x. On a 5x86 socket 3 cpu, there is a pin called CLKMUL at position R-17. On most of the earlier 486 cpus pin R-17 was marked as INC which means "internal no connect". It's likely that pin isn't connected and since the 5x86 has an internal pull up resistor on that pin, it will default to being "high" which is the "3x" multiplier setting. You need the signal on that pin to go low and that will put it in 4x multiplier mode. Try connecting a 10kohm resistor between R-17 and ground then see if that works. Since the model 2133 motherboard (the one the wiki says came with a 486 cpu) was made in 1992, it's likely there won't be any points that are connected to R-17 besides the pins on the pga168 socket. I did something like this with a ms-4144 motherboard that supports am486dx4 and intel 486 dx4 cpus but not amd 5x86 cpus. In my case I got away with putting one end of a resistor into a header I found that was connected to R-17 and the other end to a different header that was connected to ground. Hacking the board to run at a faster bus speed than 25MHz might be hard. Hopefully the isa bus clock is the cpu clock divided by 4 and not 3 in which case you can replace whatever is generating that 25mhz input clock with something else such as a 33MHz or 40MHz osillator. The chipset and motherboard may not be able to handle those speeds though.

The buck converter likely doesn’t have a large enough load on it to stabilise it’s regulation or it’ll change to intermittent cycling to minimise power consumption. Once there is enough load it’ll probably stabilise and achieve the datasheet specifications.

Very tight soldering work, great stuff. I enjoyed watching that video, looking forward to the next adventure. Wishing you all the best keep em coming .. Mick.

Man I really love this style of retro computing. Old retro gear with modern day tools/solutions to make them do things that are unnatural. 😅

Your soldering skill are absolutely next level. 😱

Great work! I had the same issue with my 486 based PC way back when. It was a Packard Bell machine, the first model they offered with a DX2 66Mhz CPU in it. When I upgraded the machine with an AMD 5x86 133 chip (also using an in socket voltage converter) there was no way of setting the multiplier on the board so the CPU always ran with a 3x multiplier. In the end I used a 40 Mhz board setting which allowed me to run the CPU at 120 Mhz. Even at only 120 Mhz it was a nice step up from the 66 Mhz chip and changing the board speed from 33 to 40 Mhz made the local bus graphics run a little faster as well.

i used to put tiny pieces of wire in the socket to set the multiplier. i once even connected the old turbo switch in front of the case to the pins from the back of the socket to change the multiplier.

I had a friend that was so into the IBM PS/1 and PS/2 that IBM reps would email and ask HIM for advice.

A couple tricks I use for soldering pin headers & sockets: Blue-Tak (the same stuff you’d use to hold a poster to the wall) works great for sticking the headers to the board and keeping them aligned while soldering. The other thing I sometimes do is to use a spare board to keep the headers aligned (it forms a sandwich with the header in between two PCBs).

When I saw you struggling with the pin headers, everything inside me screamed: put the pins in the socket first, then fit the PCB on top. Then solder while everything is held in place

Amazing video and nice way to speed things up!

Those switching regulator boards from Ali might not contain a genuine TI part, so performance could be different. Basically, it works like this. Chinese manufacturers don't want to rely on a bunch of US-designed ICs in their products, so the domestic market provides (usually inferior) ICs that are pin-compatible with those US-designs. They seldomly get marketed outside of China, some even infringe on patents and couldn't be exported either way. These parts then sometimes get relabeled as genuine parts from which they were copied, and thus enter the product cycle again as fakes.

The Socket Blaster has a clock multiplier jumper on it, "CLKMUL". Try changing the jumper to short pins 2 and 3.

Nice work on this one!

Regarding soldering and camera - have you thought about buying one of digital microscopes?Tomlov DM602 costs about $150 brand new and you can see everything and record. Mark fixes stuff channel had a review recently about the DM601

It could still be interesting to benchmark with Am5x86 due to differences in microarchitecture.

So I think I saw you skip one of the settings when you installed the P75 (the 5X86). This might be something worth checking, ill explain. The original Intel DX2 series is of P24 architecture, when the AMD 5X86 is based upon the latter P24D. The P24D would enable L1 WB, while they both are internally clock doubled. I think one more check would be worth the effort. Set all three jumpers to the DX2 settings, then with the chip installed, check if the FBS will results in 33MHz since the BIOS should set the multiplier accordingly on the identification vector during POST. However, earlier IBM builds did some funny things when it came to clock multipliers. So I can not ensure this will work as stated. I cant wait to see if this results in a win or loss (if you choose to accept the mission)!! Hope this helps, and enjoying all of your work and dedication. Keep up the great work!! Best...

I miss the days when different CPU makes would fit into the same socket.

Yeah!!!

I checked VOGONS, too. There were a couple of threads where people were trying to change from 25 to 33MHz but no dice...;-I

So much hacking of that board. Loving it. 😁

I love this kind of content, great stuff. It'd be cool to see if you can figure out a way to get the 2x multiplier working.

I still think it's funny how the PS/1 came out after the PS/2 lol.

13:35 know why it's jumpin? The buck needs a load 😁!

grattis på födelsedagen pappa

Fun project! That is some fiddly soldering!

I have a related IBM PS/1 board, no idea what model it's from since I got it without a case, but it's a weird one with a 486BLC2 and a CPU socket. My board uses a similar PLL setup to yours but it has three jumpers on the edge of the board by the SIMM sockets. Those allow for selection of 25 / 33 / 50mhz by moving the jumper to one of the three jumpers (1x jumper, 3x 2-pin jumper locations). The jumper's pins connect to Ground and a pin of a square GAL chip just next to them - which must be doing some work to specify the bus speed. The board I have has an ICS2694m chip next to the 14.3MHz crystal, which looking at the datasheet has 4 pins dedicated to speed selection, giving 16 possible combinations - which must be what the GAL is for, cutting down on having lots of jumpers and less chance of breaking things. To find out how to set the bus speed on your board, I recommend looking at the datasheet for that tiny IC next to the 14.3MHz crystal. Hopefully there's a datasheet online for that and you can trace where the CPU selection pins on the PLL go. They might be hardwired to Ground or left floating, so you may have to do some surgery (lifting an IC leg) to change the FSB if there's no provision for it otherwise.

It'd be nice to see a modern AM5 to AM4 converter kits.

J25 it apears to be related to disabling and/or selecting the soldered cpu. But why did you only tested the voltage and not also the clock while testing j23 and j24?

What clock crystal is installed IBM may have put the lowest possible to meet requirement of 486sx or possibly left circuit unpopulated for those jumpers. Not very experienced but putting ideas to check I overlook small stuff all the time.

there's unwritten rule to solder smallest and least bulky components first.

So good!

Hey, great project. These adapters... Well I am looking for 775 to 478 adapter for years (to run an old P4 CPU on a more modern s775 motherboard). If anyone has GERBER files, please share. I can do some re-degin, as daily PCB design engineer. I can also help with some of these awesome projects!

Does the 3rd jump[er on the motherboard change the clock multiplier?

Necroware probably has a way?

I put in my 2133-571 a kingston turbochip and it run flawless (see vogons IBM PS/1 multimedia max restore), otherwise pentium overdrive not, probably bios update problem. I have also an aptiva 2144-921 and PS/1 is much better with the same processor.

Would be great if you could buy these. Looks really difficult to make.

I wonder if the clock speed isnt controlled in some form of hardcoded firmware or something.

Just never copy that floppy!!!😊

What if you replaced the crystal oscillator