Reset switch for IBM 5150/5160?

Chad Fernandez fernande at
Sat Mar 26 14:30:26 CST 2005


I've never done it, but remembered reading about it.  I've looked up the 
procedure in Upgrading and Repairing PC's by Mueller.

Find the 8284a (82284 in the AT) timer chip in the PC.  When pin 11 is 
shorted to ground momentarily it will start the reset process.  Also 
shorting the "power good" line from the power supply will do the same 
thing.  The power good pin is supposed to be P8-1.

Whether it's a warm reset or a cold reset depends on the memory contents 
of a certain memory location.  Doing a Cntrl-Alt-del sets it up for warm 
resets from there on out.

If you work with early PC's, Muellers book should be on your list of 
books to buy.  I actually have 2, but different revisions, since the 
contents are a bit different in each.

Chad Fernandez
Michigan, USA

Jim Leonard wrote:

> Has anyone ever wired up a reset button/switch for their IBM PCs?  I 
> find myself powering down-then-up my 5150 three times a day when all it 
> needs is a hard reset to reboot a hung machine.  I've searched the web 
> and usenet archives for such a design or specs but haven't found 
> anything.  If I could soldier a few wires to a pushbutton, I feel like I 
> would less harsh to the machine...
> Or, does it not really matter?  Is it not a big deal to power down, then 
> power up (after 5 second delay) a 5150 or 5160?  I know IBM PCs were 
> built well, but I am unwilling to find out *how* well :)

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