Which one is it?
This seems to be a bios version or a chipset.
B587 v1.2 'P586 TX' 04/23/1998-i430TX-ALi513-2A59IPNAC-00 i430TX
B587 v1.0 'P586 TX' 10/29/97-i430TX-ALi5135-2A59IPNAC-00 i430TX ALi
Could you provide alittle more info,
like any of the numbers that are silk screened on your MoBo.
G'Luck