Early models were using Micronics (relative of Micron) usually with WD/WDC components like the video card very reliable if not a little boring .

Going closer to either side of this century things went ass tastik though if your power supply survived you might get a survivor

from what i remember all the older ones i ever encountered were very reliable and robust, its not enough to make it any more than anecdotal evidence but never heard bad things about them way back. old 90's examples still appear in circulation now and then a little rough around the edges but still ok

The P-II and P-III models I have come across all have worked on power up like this one I cleaned up and gave away over at vcfed.org. Many used rebranded Intel motherboards which were good quality for the most part.