VOGONS


First post, by BLockOUT

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i was looking for some manuals on old IBM PS/1 systems because i wanted to know what they offered back then as upgrade options for their pc.
Well, i thought they were very open in terms of an upgrande ....

dam i was so wrong. For example if you bought a 486dx2-50 computer you could not upgrade to a dx2-66.
And even worse, the only option they offered was to buy one of those (now super expensive) P24T pentium overdrives 63 and overdrive 83

http://ps-2.kev009.com/pcpartnerinfo/ctstips/bcaa.htm

original I Upgrade
DX2/50 > P24T-63
DX2/66 > P24T-83

I would like to know if there is any upgrade alternative to that.

i guess these things don`t work for this?
pentiums.jpg

Reply 2 of 22, by BLockOUT

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Caluser2000 wrote on 2021-05-01, 04:02:

A lot of IBM PS/1s had a 25mhz/33mhz jumper.

The 486DX2/66 cpu may not have been available when theb manual was produced.

P24T-83 October, 1995
486 DX2-66 date 10-Aug-92

so the manual must have been updated

Reply 3 of 22, by TheMobRules

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I'd say that if the P24T is supported then any other 5V overdrive should work. P24T is the quirkiest Intel Socket 3 CPU in the sense that it needs specific motherboard support, and even certain motherboards that claim to be compatible with it don't work properly due to last minute changes in the specs by Intel.

A DX2 or DX4 overdrive is not that different from a regular DX-class CPU, so unless the BIOS on that machine is specifically programmed to reject newer CPUs it should work.

Reply 5 of 22, by dionb

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"Supported by IBM" doesn't automatically mean "nothing else will work". It might though as IBM BIOSs are hardly the most forgiving. If you want 'very open' go for a good brand-name motherboard in a generic system, not proprietary OEM stuff.

But that just means it's a challenge. Is this the motherboard? http://www.win3x.org/uh19/public/motherboard/ … anual/34351.pdf

No speed jumper, but that 'undocumented' J50 just asks to be messed with. See if that moves you from 50 to 66MHz or vice versa. If not, the 25MHz/33MHz bus speed is coming from a crystal you need to replace to change the clock. Do you currently have a DX/2-66 or a DX/2-50?

I'd say it's worth trying with an ODP100 if you can find one for a price worth experimenting with.

Reply 6 of 22, by PC-Engineer

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The P24T can have their quirks from DMA problems up to destroying himself and the board. I am at @dionb and would recommend a DX4 ODPR 100. It would run in 99,9% of all 486 with LIF and ZIF socket - and it is a real, genuine intel 486.

1994/1995 - Socket3 - ASUS SV2GX4 / POD 100MHz / 64MB / SCSI - Windows 95

Reply 7 of 22, by BLockOUT

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dionb wrote on 2021-05-02, 22:53:
"Supported by IBM" doesn't automatically mean "nothing else will work". It might though as IBM BIOSs are hardly the most forgivi […]
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"Supported by IBM" doesn't automatically mean "nothing else will work". It might though as IBM BIOSs are hardly the most forgiving. If you want 'very open' go for a good brand-name motherboard in a generic system, not proprietary OEM stuff.

But that just means it's a challenge. Is this the motherboard? http://www.win3x.org/uh19/public/motherboard/ … anual/34351.pdf

No speed jumper, but that 'undocumented' J50 just asks to be messed with. See if that moves you from 50 to 66MHz or vice versa. If not, the 25MHz/33MHz bus speed is coming from a crystal you need to replace to change the clock. Do you currently have a DX/2-66 or a DX/2-50?

I'd say it's worth trying with an ODP100 if you can find one for a price worth experimenting with.

hey dion
you nailed it, seems that you have a lot of experience on ps/1 2168 systems?

-Here are some pictures of my motherboard. i included a picture of the crystal that is near the CPU. ( i have no clue of what is he mhz of that crystal.)
1. not sure if i should try to buy a new crystal for higher cpus., if i have to, what kind of crystal should i buy? any specific link to the product i would really appreciate, does it have to say "66.0 mhz"?

2. So ..it is safe to try with a 486 overdrive 100 ?
what jumper settings should i choose for J25, j31 and j24 ? before putting one of those on the board? since that would be out of the manual im not sure what jumpers to move
I have 2 overdrive 100, i tend not to use them because they get extremely hot to touch, but if it works i will put a nice 80mm fan sending air to the overdrive heatsink directly

My machine is a 2168 and the model is L88[/u] and the sticker says its a 50mhz cpu.

It works perfectly. I had forgot that the vga output of ps/1 has one of the pins sealed, i had to install a trident isa card, and flip the vga jumper to onboard disable, then edit some inis in win3.1 so it botted really nice and im able to use windows 3.1

The good thing about this pc is that the hard drive is intact, and it has the original software for win3.1 ps/1 demos,and also the is a recovery directory in c: , full of zip files for floppy recovery.
(no clue on how these zip files work, perhaps i just need to format floppy drives and unpack those zips into floppy disks, as there was no executable in that directory.

my plan is to take out the HDD, and use one of those IDE to usb readers in order to make a full backup of the hard drive using my laptop with acronis or any other program.

and in the future i would like to install cache chips and a soundblaster16, perhaps i can just take the cache from one of my 486 dead motherboards and install the cache on this ps/1

Whats-App-Image-2021-05-04-at-1-21-32-PM-1.jpg
Whats-App-Image-2021-05-04-at-1-21-32-PM.jpg

Reply 8 of 22, by dionb

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BLockOUT wrote on 2021-05-04, 18:54:

[...]

hey dion
you nailed it, seems that you have a lot of experience on ps/1 2168 systems?

Not really, my mother had a very late Pentium version in her Aptiva 25 years ago, but I wasn't allowed to touch its insides. And I have a slightly different 2168 board here with IBM/Cyrix Blue Lightning DX2 on it. But the rest is just general knowledge of 486 systems and guesswork.

-Here are some pictures of my motherboard. i included a picture of the crystal that is near the CPU. ( i have no clue of what is he mhz of that crystal.)

It says "143xxxx", so that's 14.318MHz, which sets the clock for everything on the board except CPU, VLB and RAM. If you're in luck, there's another crystal in there somewhere which will have "25" on it. If not, then there's a PLL chip that derives 25MHz from the 14.318MHz output.

And... it's the PLL. That av9155-01cw20 chip next to the crystal is a "Low Cost 20-Pin Frequency Generator", with decscription: "The device uses a 14.318 MHz crystal to generate the CPU and all peripheral clocks for integrated desktop motherboards."

In that case you can't replace the crystal for a faster one, as that will utterly mess up the timing of all I/O depending on that clock (FDD and HDD will cease to work for starters).

But all is not lost. If I look at the datasheet for that chip, I see it's configurable using pins 19 and 20 for FS1 and FS0. Relevantly it has an internal pull-up, so either a pin is connected to GND (for logical 0) or not connected at all (for logical 1).

1. not sure if i should try to buy a new crystal for higher cpus., if i have to, what kind of crystal should i buy? any specific link to the product i would really appreciate, does it have to say "66.0 mhz"?

No, the DX/2 isn't called /2 for no reason. It has a 2x internal clock multiplier, so internally it runs at 50 or 66MHz, but externally it communicates at 25 or 33MHz. You want to bump 25MHz up to 33MHz.

Now, 25MHz CPU speed has FS1 and FS0 both set to 0; 33MHz has FS1 set to 0 and FS0 set to 1. So what you need to do is to get that FS0 pin 20 set to 1.

If I'm right about open = high and closed = low, that means that it's currently connected to ground. If so, sever that connection (de-solder/cut the leg) and you increase CPU bus clock to 33MHz. If I'm wrong it's marginally more complex, but still very doable: in that case neither pin 19 or 20 are currently connected to anything and all you need to do is to connect pin 20 to GND. Anything connected to GND will do; pin 15 on the PLL for example, but you can use anything else, up to and including the GND pin on any header. An advantage to the latter is that you can include a switch so you can switch between 25 and 33MHz at will. You can also add a switch in between in the first case (leg is now connected) for the same purpose.

You can even switch it on the fly, as the datasheet says:

Frequency Transitions - A key feature of the AV9155 is its ability to provide smooth,glitch-free frequency transitions on the CPU and 2XCPU clockswhen the frequency select pins are changed.

Now, your pic of the oscillator crystal is great, but only captures half the PLL, the relevant pins are of course (Murphy...) just out of frame. The second pic shows all the chip, but not in enough detail to figure out if 19 and 20 are connected to anything or not. If you could make a close-up of the side not on your first pic (i.e. the side opposite the one where the yellow bodge wire is connected) we can take a look for you.

But before going down this path, have you checked what J50 does? I wouldn't be at all surprised if that connects FS0 on the PLL to GND (or not if open).

2. So ..it is safe to try with a 486 overdrive 100 ?
what jumper settings should i choose for J25, j31 and j24 ? before putting one of those on the board? since that would be out of the manual im not sure what jumpers to move
I have 2 overdrive 100, i tend not to use them because they get extremely hot to touch, but if it works i will put a nice 80mm fan sending air to the overdrive heatsink directly

The key to Intel Overdrives is that they are exact drop-in replacements for the original CPUs, in this case i486DX or i486DX/2 CPUs. So leave jumpers exactly as they are and if it's going to work, it will work at 75MHz now, and 100MHz if you get the clock up to 33MHz.

My machine is a 2168 and the model is L88[/u] and the sticker says its a 50mhz cpu.

It works perfectly. I had forgot that the vga output of ps/1 has one of the pins sealed, i had to install a trident isa card, and flip the vga jumper to onboard disable, then edit some inis in win3.1 so it botted really nice and im able to use windows 3.1

That 'sealed' pin is perfectly normal for old VGA without DCC:
VGA-Pinouts-16fe4wk.png

But if your monitor requires DCC, you need the card. In any event it should work fine the way you have done it.

The good thing about this pc is that the hard drive is intact, and it has the original software for win3.1 ps/1 demos,and also […]
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The good thing about this pc is that the hard drive is intact, and it has the original software for win3.1 ps/1 demos,and also the is a recovery directory in c: , full of zip files for floppy recovery.
(no clue on how these zip files work, perhaps i just need to format floppy drives and unpack those zips into floppy disks, as there was no executable in that directory.

my plan is to take out the HDD, and use one of those IDE to usb readers in order to make a full backup of the hard drive using my laptop with acronis or any other program.

and in the future i would like to install cache chips and a soundblaster16, perhaps i can just take the cache from one of my 486 dead motherboards and install the cache on this ps/1

That would give performance a very nice boost, highly recommended.

Reply 9 of 22, by BLockOUT

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dionb wrote on 2021-05-02, 22:53:

"Supported by IBM" doesn't automatically mean "nothing else will work". It might though as IBM BIOSs are hardly the most forgiving. If you want 'very open' go for a good brand-name motherboard in a generic system, not proprietary OEM stuff.

thanks dion for all the detailed information.

here are some more pictures
so im with a multimeter and im checking continuity between pin#20 and ground. From what i understood pin#20 should be grounded after i set an unkown jumper.

-Jumper50 i moved the position and nothing, there is no continuity between pin20 and ground.
-i found some unsoldered jumpers next to turbo jumper J37, (J35 and j36) but i tried jumping them with a paper clip and then checking continuity between pin20 and ground and i got nothing.
- Are you sure #20 is the one that should have ground?, also on picture that leg goes to a bia, on the back of the motherboard maybe.

if you need more HQ picts i can upload them to mediafire if you want.

image-2021-05-04-195923.png
ppl.jpg
ppl2.jpg
ppl3.jpg

Reply 10 of 22, by kingcake

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BLockOUT wrote on 2021-05-01, 03:39:
i guess these things don`t work for this? https://i.ibb.co/VHKGfzY/pentiums.jpg […]
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i guess these things don`t work for this?
pentiums.jpg

What do I search for to buy one of the adapters on the right?

Reply 12 of 22, by dionb

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BLockOUT wrote on 2021-05-04, 23:00:
[...] […]
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[...]

thanks dion for all the detailed information.

here are some more pictures
so im with a multimeter and im checking continuity between pin#20 and ground. From what i understood pin#20 should be grounded after i set an unkown jumper.

-Jumper50 i moved the position and nothing, there is no continuity between pin20 and ground.
-i found some unsoldered jumpers next to turbo jumper J37, (J35 and j36) but i tried jumping them with a paper clip and then checking continuity between pin20 and ground and i got nothing.
- Are you sure #20 is the one that should have ground?, also on picture that leg goes to a bia, on the back of the motherboard maybe.

No continuity with GND now? Then I'd suggest to give it some. If you have a steady hand, you can try with a jumper wire on the fly and see the results. That via doesn't surprise me - this board was also released with 33MHz speed, so no doubt that via would be connected with 0 Ohm 'resistor' to GND in that case.

Reply 13 of 22, by BLockOUT

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dionb wrote on 2021-05-05, 07:24:
BLockOUT wrote on 2021-05-04, 23:00:
[...] […]
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[...]

thanks dion for all the detailed information.

here are some more pictures
so im with a multimeter and im checking continuity between pin#20 and ground. From what i understood pin#20 should be grounded after i set an unkown jumper.

-Jumper50 i moved the position and nothing, there is no continuity between pin20 and ground.
-i found some unsoldered jumpers next to turbo jumper J37, (J35 and j36) but i tried jumping them with a paper clip and then checking continuity between pin20 and ground and i got nothing.
- Are you sure #20 is the one that should have ground?, also on picture that leg goes to a bia, on the back of the motherboard maybe.

No continuity with GND now? Then I'd suggest to give it some. If you have a steady hand, you can try with a jumper wire on the fly and see the results. That via doesn't surprise me - this board was also released with 33MHz speed, so no doubt that via would be connected with 0 Ohm 'resistor' to GND in that case.

thanks Dion, no continuity with pin20 and ground, and i was not able to make any jumping those unsoldered jumpers with a paper clip either.

-Before doing what you said (since im scared of breaking this untouched IBM beauty), In the next few days, i will take the motherboard out, then check where the hell is that bia on pin20 going to. I will send you a private message with results and pictures of where it goes to.

- So per your last comment, there is no need to lift the #20 pin out of the pcb? i can leave it just like that, and solder a tiny wire to leg#20 and the other side i can solder the wire to a negative side of a capacitor for example ?

Reply 14 of 22, by dionb

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BLockOUT wrote on 2021-05-05, 14:20:
[...] […]
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[...]

thanks Dion, no continuity with pin20 and ground, and i was not able to make any jumping those unsoldered jumpers with a paper clip either.

-Before doing what you said (since im scared of breaking this untouched IBM beauty), In the next few days, i will take the motherboard out, then check where the hell is that bia on pin20 going to. I will send you a private message with results and pictures of where it goes to.

- So per your last comment, there is no need to lift the #20 pin out of the pcb? i can leave it just like that, and solder a tiny wire to leg#20 and the other side i can solder the wire to a negative side of a capacitor for example ?

Definitely no need to lift the pin if it's not currently connecting to GND. As for the rest, I'd recommend posting it here rather than via PM. I'm far from the most experienced person here (note that I wasn't sure about GND being logical 0 or 1...), so best keep others in the loop too.

Reply 15 of 22, by BLockOUT

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dionb wrote on 2021-05-05, 15:56:

Definitely no need to lift the pin if it's not currently connecting to GND. As for the rest, I'd recommend posting it here rather than via PM. I'm far from the most experienced person here (note that I wasn't sure about GND being logical 0 or 1...), so best keep others in the loop too.

took some time to take the motherboard out but its bad news, they included a light green coating all over the board and below that coating there is a hard green coating, the result is that you cannot see the traces of the board, not in the back, and not in the front so, its all blind mode.

Back of the board is only full bias i did found some bias that had continuity with pin20 but nothing of interest that could be later be connected to ground..

I tried to experiment in continuity mode to see what bias on the back connected to pin20, and i found about 5, one of the interesting ones is this component R251 with has a marking of "331".
the component is near the turbo jumper. That component gave me continuity with ground on one end, and the other end of that component has continuity with pin20

but since you are not able to see the traces, it might be dangerous to actually test with what the hell they did and what it connects to, the only way to see them would be with an x-ray machine.

331.jpg

Reply 16 of 22, by Intel486dx33

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I have several IBM Ps/1 and have upgrade them to the Max with CPU’s and Cache and RAM.

I will say that save your MONEY.
For best value performance just change the jumper to 33mhz bus and install a 486dx-66 in Overdrive socket.
Add 256mb of cache.
The Intel Overdrive 486dx4-100 will only get you about a 10% performance boost over the 486dx2-66

Either way the game play performance is not going to change so don’t bother with it.
There is better game play performance in going from a 486dx-50 to a 486dx-66

So I would max out with the 486dx-66 and 256mb of cache if you can.

But if you are looking for best DOS game play performance then get a Pentium 100 thru Pentium MMX 233.
I like the Pentium MMX 233.
The Pentium MMX 233 runs like Cadillac and plays most DOS games and apps flawlessly in good performance.
Use a BX440 motherboard and 32mb of EDO ram.

That IBM PS/1 is just a collectors item. Not really great at playing DOS games.
Just restore it with what ever hardware will work and leave it at that.
But definitely install the original image software which you can find online.

Reply 17 of 22, by BLockOUT

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Intel486dx33 wrote on 2021-05-05, 19:23:
I have several IBM Ps/1 and have upgrade them to the Max with CPU’s and Cache and RAM. […]
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I have several IBM Ps/1 and have upgrade them to the Max with CPU’s and Cache and RAM.

I will say that save your MONEY.
For best value performance just change the jumper to 33mhz bus and install a 486dx-66 in Overdrive socket.
Add 256mb of cache.
The Intel Overdrive 486dx4-100 will only get you about a 10% performance boost over the 486dx2-66

Either way the game play performance is not going to change so don’t bother with it.
There is better game play performance in going from a 486dx-50 to a 486dx-66

So I would max out with the 486dx-66 and 256mb of cache if you can.

But if you are looking for best DOS game play performance then get a Pentium 100 thru Pentium MMX 233.
I like the Pentium MMX 233.
The Pentium MMX 233 runs like Cadillac and plays most DOS games and apps flawlessly in good performance.
Use a BX440 motherboard and 32mb of EDO ram.

That IBM PS/1 is just a collectors item. Not really great at playing DOS games.
Just restore it with what ever hardware will work and leave it at that.
But definitely install the original image software which you can find online.

What jumper? thats what we are trying to find , it doesn´t have 33mhz jumper.

Reply 18 of 22, by dionb

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Er, that's pretty par for the course for his posts... but it has set me thinking. That J37 is in the general vicinity of R251 and the PLL. According to the documents that's for the "Turbo switch". Interesting as I'm not sure that case has one, and even if it did, there's a jumper on J37 now, not a lead to a switch. Also it's in a block with J35 and J36, which sort of sounds like FS2, FS1, FS0 to me.

What happens if you remove that jumper cap from J37?

Reply 19 of 22, by Intel486dx33

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BLockOUT wrote on 2021-05-05, 19:27:
Intel486dx33 wrote on 2021-05-05, 19:23:
I have several IBM Ps/1 and have upgrade them to the Max with CPU’s and Cache and RAM. […]
Show full quote

I have several IBM Ps/1 and have upgrade them to the Max with CPU’s and Cache and RAM.

I will say that save your MONEY.
For best value performance just change the jumper to 33mhz bus and install a 486dx-66 in Overdrive socket.
Add 256mb of cache.
The Intel Overdrive 486dx4-100 will only get you about a 10% performance boost over the 486dx2-66

Either way the game play performance is not going to change so don’t bother with it.
There is better game play performance in going from a 486dx-50 to a 486dx-66

So I would max out with the 486dx-66 and 256mb of cache if you can.

But if you are looking for best DOS game play performance then get a Pentium 100 thru Pentium MMX 233.
I like the Pentium MMX 233.
The Pentium MMX 233 runs like Cadillac and plays most DOS games and apps flawlessly in good performance.
Use a BX440 motherboard and 32mb of EDO ram.

That IBM PS/1 is just a collectors item. Not really great at playing DOS games.
Just restore it with what ever hardware will work and leave it at that.
But definitely install the original image software which you can find online.

What jumper? thats what we are trying to find , it doesn´t have 33mhz jumper.

What model # does the back label of your IBM PS/1 read ?
Something like 5155

Okay, I see from the photos that this motherboard is capable of accepting the Intel 486dx2-66 CPU
And 256kb of cache.
And 16mb of ram

That is what you will needed to get the best value performance out of this computer.
So not to spend too much money on it that really will not improve game performance.

Just change the jumper to 33mhz.