Boy am I glad that I didn't start out with one of thos PS/2 computers. I started the upgrade operation out by spending $235 for a AMD386DXL-40 Forex upgradable mother board from Midwest Micro. When it was time to upgrade I bought a Intel 486DX2-50 cpu for $350 and was finished. I still don't see why they ever made the 486\50 cpu at all. Its to fast for both ISA and LB and VESA boards..   Some test results taken on my mb and 486DX2-50 cpu and some others...  ------------------------------------------------------------------------------ X-TAL UPGRADES & SPECS - TURBO MODE TESTS - WITH FAN & HEATSINK KIT - ISA BUS  X-TAL MHZ                    CPU MHZ   CPU SPEED MHZ    FPO MHZ   VIDEO CHR/MS  40.00 -386AND /3=13.33MHZ     40.544     62.37            ---       6510.00 40.00 -386AMD /4=10.00MHZ     40.544     62.37            ---       6467.00 *  50.000-486DX2-50 /2=12.5MHZ   50.041     167.22          441.53     6105.00 52.361-486DX2-50 /2=13.1MHZ   52.703     176.03          464.81     6425.00 * 54.058-486DX2-50 /2=13.5MHZ   54.120     180.81          477.40     6642.00 56.644-486DX2-50 /3=9.37MHZ   56.220     189.46          500.25     4593.00 66.666-486DX2-50 /3=11.1MHZ   66.759     222.99          588.81     5401.00  WITH ALL TESTS THE 486DX2-50 RAN ICE COLD! NOT EVEN UP TO ROOM TEMP DID IT GO! ------------------------------------------------------------------------------ 50.000-486DX50   /?           49.998     167.12          408.89     2463.00 ??.???-486DX2-66 /?           84.234     224.00          372.00    10570.00 ------------------------------------------------------------------------------ CPU/ISA BUS        X-TAL MHZ      BUS SPEED/MHZ       SPEEDSTAR 24X VIDEO CARD  AMD386DXL-40       40.000         /2 = 20.00 MHZ      INOPERATIVE AMD386DXL-40       40.000         /3 = 13.33 MHZ      6510.00 CHR/MS AMD386DXL-40       40.000         /4 = 10.00 MHZ      6467.00 CHR/MS AMD386DXL-40       40.000         /5 =  8.00 MHZ      4020.00 CHR/MS AMD386DXL-40       40.000         /6 =  6.66 MHZ      NOT TESTED ------------------------------------------------------------------------------ 486DX2-50          50.000         /2 = 12.51 MHZ      6105.00 CHR/MS 486DX2-50          50.000         /3 =  8.34 MHZ      NOT TESTED 486DX2-50          50.000         /4 =  6.25 MHZ      NOT TESTED 486DX2-50          50.000         /5 =  5.00 MHZ      NOT TESTED 486DX2-50          50.000         /6 =  4.16 MHZ      NOT TESTED ----------------------------------------------------------------------------- 486DX2-50          56.64          /2 = 14.16 MHZ      6826.00 CHR/MS 486DX2-50          56.64          /3 =  9.44 MHZ      4593.00 CHR/MS 486DX2-50          56.64          /4 =  7.08 MHZ      NOT TESTED 486DX2-50          56.64          /5 =  5.66 MHZ      NOT TESTED 486DX2-50          56.64          /6 =  4.72 MHZ      NOT TESTED ---------------------------------------------------------------------------- 486DX2-50          66.66          /2 = 16.67 MHZ      NOT TESTED 486DX2-50          66.66          /3 = 11.11 MHZ      5401.00 CHR/MS 486DX2-50          66.66          /4 =  8.33 MHZ      NOT TESTED 486DX2-50          66.66          /5 =  6.67 MHZ      NOT TESTED 486DX2-50          66.66          /6 =  5.56 MHZ      NOT TESTED ---------------------------------------------------------------------------- 486DX2-50          54.12          /2 = 13.53 MHZ      6642.00 CHR/MS 486DX2-50          52.36          /2 = 13.17 MHZ      6425.00 CHR/MS