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IBM PS/2 Model 25 upright built in monitor CPU "upgrade"

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kiyotewolf

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Is it possible to drop in a 8088 cpu chip from a IBM PCjr in another IBM, a PS/2 Model 25, the upright with the built in screen & MCGA graphics?

Going from an 8086 to 8088. Like going from a model T to a Lamborgini.

What could I possibly gain from this, if it would even work.



~Kiyote!
 
It's not possible, and in fact would result in a decrease in performance. The 8088 has an 8-bit external data bus (hence the 88) while the 8086 has a 16-bit external data bus. The pinouts are different, and you'd lose half your data bus width even if you could swap them out.
 
kiyotewolf said:
Is it possible to drop in a 8088 cpu chip from a IBM PCjr in another IBM, a PS/2 Model 25, the upright with the built in screen & MCGA graphics?

Going from an 8086 to 8088. Like going from a model T to a Lamborgini.

What could I possibly gain from this, if it would even work.
Click to expand...

Expanding on the correct response you have already received, the 8088 of the PCjr was run at 4.77MHz, and rated lower than the 8086 8MHz in that version of the Model 25. You can substitute an NEC V30 CPU for a slight increase, but that is the only gain solely from any possible CPU swap. There was also a 286-10MHz and 386SX-16/20MHz version of the Model 25 from IBM.

Aftermarket upgrades were a planar swap, like the "Reply 25" able to go up to a 486DX4-100, or from PC Enterprises, able to run an AMD 486DX4-133...

That is more of your Model T to Lamborgini comparison...

IBM also made a range of slightly larger cases and capabilities called the "EduQuest"...
 
IBMMuseum said:
IBM also made a range of slightly larger cases and capabilities called the "EduQuest"...
Click to expand...
Sounds like he has the Model 25 version of what became the EduQuest. I had several of these from the local school system when I was in middle school -- unfortunately, two of them were destroyed by lightening, and the other became a donor for the more-capable regular Model 25 I acquired.
 
Thanks for the technical answers.
I'm concerned about various compatibilty (SPELLING FAIL) for things like INTERLNK & stuff.
I don't remember if I got INTERLNK to work on that computer or not.
I do have something I want to try. I have an IBM PS/2 something, it's just a rectangle, and it has a hard drive in it.
My PS/2 25 has a IDE port for a hard drive, but no 4 pin power connector.
I'm thinking of running an IDE cable from the inside of the standalone IBM PS/2 box, out and into the IBM PS/2 25 motherboard, and powering the hard drive from the existing computer/case it's in, since I can't get any kind of power from the MODEL 25.
I'm aware there is probably an IN-IDE cable supply for power, from the Model 25, because the floppy is setup as such, but I'm working around that.
I'd have to keep one on top of the other, just to keep things close enough so they would connect.

Ideas? Critique of what I wanna do?

I wanna get a hard drive on my PS/2 25. I figure, the hardware should be near enough in age to be technically compatible.
I know there is a ZIP driver out there, because I have plenty of LPT1: zip drives to add external storage, or storage period, but I gotta send off for the driver with paypal & such, that's for later.

On another side note, I have a PS/1 tower which I got from a literal junk store in ABQ, NM!
 
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Unfortunately, the hard disk connector in there isn't IDE. It's a "planar" IBM proprietary format, and the drives, even though they share similar connectors, differ even by the model of PS/2 they're used in.

The Model 25 includes built-in ISA slots, so you should be able to add an XT-IDE card for use as a hard drive. I have a Model 25, and ran into the same power problem you've found, and came up with a pretty good solution to it:

http://glitchwrks.com/vintage/xtideflash.html#xtidemod

This arrangement pulls power from the ISA bus, and routes it through IDE pin 20 so there are no external cables. You just plug the card in and go! I've tested the XT-IDE and the Flash module arrangement with my Model 25, so you can be pretty sure it will work with your setup.
 
I'm going to get the demo driver for the ZIP drive 100 MB from that one guy.. Zaphod Beeblebrox?
That will be MORE than enough extra storage & active storage for me anyways, and less headache.
Hope it works with my Model 25.



~Kiyote!

Going to use it as a digital photo frame, and other stupid cute uses.
 
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