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I need some help doing an internal VGA upgrade on my hotrod PS/2 model 25-286

Simplethings

Member
Joined
Jul 13, 2016
Messages
24
Location
New Orleans
Alright guys, I have been working on my favorite nostalgic machine for a while now and finally have got the rare bits I needed to make it a more capable machine.

After looking for a year for 4MB of special PS/2 RAM it finally popped up, and if you have a PS/2 model 25 or 30 I suggest you look on Ebay now because the seller has more.

I also got the Kingston SX Now! 33Mhz CPU upgrade.

Here are the results from a single benchmark of my upgrade:

3DBench
Stock PS/2 Model 25-286 10Mhz:
2.6
Wolf 3D Benchmark FPS:
4.4

PS/2 Model 25-286 w/ 33Mhz Kingston SX Now!
5.1
Wolf 3D Benchmark FPS:
7.7


As you can see I got about twice the original performance after the upgrade. I felt like the 256kb integrated VGA was holding it back so I threw in a 2MB ISA STB Nitro card I had pulled from a 486 I got from a thrift store and ran an external monitor. HOLY CRAP BETTER:

PS/2 Model 25-286 w/33Mhz Kingston SX Now!
8.1
Wolf 3D Benchmark FPS:
13.3


As you can see the ISA VGA card really takes this system into overdrive. The CPU by itself took Wolf3d from a slideshow to "playable", but the VGA card makes it smooth, a responsive.

I want to do a modification to my system like the one that evildragon did in this thread:
http://www.vcfed.org/forum/showthread.php?35786-IBM-PS-2-Model-25-VGA-Mod-Explained

basically wiring the PS/2 model 25's integrated monitor to the internal ISA card rather than the integrated VGA. I'm not sure if I can just do this with the card I have already without causing damage to my CRT. Unlike his monochrome monitor mine is color already. Do you guys think I should just try it and see what happens?
 
@ $35 a simm? F*** that noise. 90% of the stuff that guy sells, is about a decimal place off in terms of price.

To me, your asking the system to do too much. The charm of the 25 & 30 is the MCGA (and extension cga) games on proper slow hardware. If I was in your position, I'd look to building a 386 for the early vga games.

As for the mod, I hate hard modding things. I would be more inclined to make an adapter cable. Cut up a standard vga cord, solder a 2x5 header on one end, and you dont run the chance of harming old hardware.
 
The charm of the 25 & 30 is the MCGA (and extension cga) games on proper slow hardware.

My PS/2 is a Model 25-286, it's already got VGA graphics, but with only 256kb of vram.

I could understand your point about building another system, but this is not about having any early 386. This is the same computer I had in Highschool in the mid 90's. I left mine someplace long ago and now having the most powerful version of my specific machine is what makes it fun for me.

As for his prices: after scraping forums, overstock parts warehouses, and ebay a year for this to pop up literally anyplace I was fine with paying his price and being done with it.

Anyway, Here is a screenshot of my TopBench results before and after the 2MB STB Nitro ISA card:
ps2bench.jpg

As for the mod, I hate hard modding things. I would be more inclined to make an adapter cable. Cut up a standard vga cord, solder a 2x5 header on one end, and you dont run the chance of harming old hardware.

That's my plan, my only concern is possible damage to the monitor due to incompatible frequencies.
 
I don't know if the monitor will handle the signals. As long as you keep to 640x480 max, I cant imagine there being a problem. Worst case scenario, something pops and you need to replace some parts on a board.
 
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