Ibm 600x errors 173, 163 & 301

On post i get these errors. I click OK & go to date screen (date/time is correct as I have replaced the cmos battery) Click OK, get 2 beeps & then nothing. screen just sits there. Keyboard is working as buffer fills up after 15 keystrokes. Press ctrl,alt,dlt & it comes back with error codes 173 & 163, click OK & it takes me back to the date screen & round the circle again. Pressing & holding F1 during power up makes no difference whatsoever, i.e. just acts as if I wasn't pressing F1. This PC was working fine until about 3yrs ago when it just got put away & left, taken out last week, cmos battery dead so replaced & the above happens. I've seen many repetitions of this problem over the web but never an answer, just that it must be the battery. But as stated, I've replaced the battery & it is holding the date/time overnight with no other power.