I'm not that familiar with the PS/1 and PS/2 but I looked into using a similar processor in a PS/2 Model 90 XP I received a year or two ago and I did some research on this same upgrade since I have a couple of PODP5V83 processors myself.

I never got around to trying it myself, but I did find this:
https://comp.sys.ibm.ps2.hardware.narkive.com … -64mb-on-lacuna

Quote from a poster on that page:
"The Model 90 takes a processor complex and is
roughly the same form factor. While the original configuration was always a
486 (no processor complex exists that can take the Pentium OverDrive
63/83MHz CPUs), the Model 90 can use the Pentium 60, 66 and 90MHz complexes
from Server 95 or PC Server 500 systems. (There also exists the so-called
Type 4 N complex that has a 486 DX2 66MHz CPU but can also use larger
amounts of RAM--same as the Pentium units.)"

Again I'm not sure if any of this is relevant for the PS/1 as well, but if this statement is accurate then no 486 complex (large card that holds the CPU) for my system is compatible with these particular processors. I have found some scattered posts in other places mentioning this same thing, though I don't have the links handy. Some places mention that some other types of 486 upgrade processors tend to work okay... for example, ones that use an AMD 5x86.

Since you have tried so many chips, it seems likely that the system just doesn't support the PODP5V83.

Some crazy people mention snapping off a pin to make it work in other PS/2 models without an interposer, but I do not recommend doing that even if you do more research and find that it does work.

I know that PS/1 and PS/2 systems are very different. I just wanted to mention this because it seems that the PODP5V83 is not 100% compatible with all 486 systems that seem like they should otherwise work with it.

fabiensanglard wrote on 2025-03-10, 05:36:

I am attempting to put the final touch on my IBM PS/1 2168 max restore with a Pentium 83Mhz upgrade from the factory 486 DX2-66. […]
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I am attempting to put the final touch on my IBM PS/1 2168 max restore with a Pentium 83Mhz upgrade from the factory 486 DX2-66.

My model is 2168-594. I have checked out the documentation and installed the PODP5V83 with the notch is in the lower right corner and I adjusted the jumper 25 to position 2-3.

The attachment doc.MP.jpg is no longer available

The attachment cpu.MP.jpg is no longer available

The attachment jumpers.jpg is no longer available

The machine starts, the CPU fan spins but the machine does not POST (no BIOS or memory check).

Troubleshooting done s0 far:

- I have tried one PODP5V83 from ebay. No POST.
- I have tried a BOXPODP5V83 (fresh from an unopened box). No POST.
- If I put back the 486-DX66 it works again.

The attachment BOXPODP5V83.MP.jpg is no longer available

I am unsure what to check next. Has anybody else successfully performed this kind of upgrade?

Needs an EPROM upgrade? - https://www.infania.net/misc/eprmhtml/eprm/h229.html

Thanks Hoader. I just found the same link you posted. I also found this one with an interesting precision.

If you are installing a Pentium Overdrive processor, an EPROM upgrade is needed. If your machine has 2 SIMM sockets, the EPROM FRU is 07H0993. If your machine has 4 SIMM sockets, the EPROM FRU is 07H1001.

Which means my machines needs

1P/N 07H1001

Now, where can I find it? I did find a P3FLASH.EXE but that is for Aptiva if I read that correctly.

I am currently combing the Archive of the IBM PC Company BBS FTP Site.

I found a few interesting things but most noteworthy, the 486 OverDrive Upgrade Compatibility (rev. 07.145F) which mentions BOXSX2ODP-50, BOXDX2ODP-66, and DX4ODPR-100 computability with IBM PS/1 2133, 2155, and 2168. It looks like it is all over the place but I could try to fallback to a DX100 upgrade which would still help DOOM.

1Positive Test Results from Unsupported Processor Upgrades:
2----------------------------------------------------------
3
4NOTE:  The following list indicates processors which we have found to work
5in some systems, yet are not recommended nor supported by IBM.  In most
6cases, the upgrade is not supported because of either manufacture dates of
7system boards prior to their upgrade processor's introduction or because of
8system board instability at higher processor speeds.  In any event, IBM
9claims no responsibility for damage occurring from the installation of the
10processors listed below into the system units listed below.
11
12Intel DX4 / 100 MHz OverDrive (DX4ODPR-100, version 1.0 only):
132133 Models:
1418A, 20C, 21C, 23C 
152155 Models:
1643C, 41T, 39E, 52C, 50T, 48E, 45V, 55V, 78C, 79C, 87C, CC1
172168 Models:
1837C, 33T, 31E, 56C, 54T, 51E, 28V, 58V, 38C, 57C, BB1, US1
19
20Intel DX4 / 100 MHz OverDrive (DX4ODPR-100, version 1.1 only):
212133 Models:
2218A, 20C, 21C, 23C 
232155 Models:
2478C, 79C, 87C, CC1
252168 Models:
2638C, 57C, BB1, US1

I also need to take the time to investigate what is in the 2168 Advanced Diagnostics Diskette

There is also Performance Upgrading: A Look at IBM PS/1 486 Computers which mentions Pentium Overdrive support.

Intel P24T Pentium OverDrive:

1The recent release of the P24T Pentium OverDrive processor has brought
2Pentium technology to existing 486 platforms.  Operating at a 5:2 processor-
3to-bus speed ratio, the P24T allows faster processor power at a lower MHz
4rating.  For example, for a 25 MHz computer the P24T will operate at about
563 MHz.  Likewise, current 33 MHz computers will power the P24T at 83 MHz.
6By processing more instructions per cycle, an 83 MHz P24T can process
7faster than a 100 MHz DX4.  The current list price for the P24T Pentium
8OverDrive is about $550.  The 63MHz Pentium OverDrive is currently
9available from Intel, while the 83 MHz P24T version is scheduled to be
10released at a later date.