If your memory says it is 70ns then it is NOT EDO type memory. It is probably Standard Simms type. Later 486 PC's will accept EDO but older PC's only accept standard. Some later 486 PC's like their memory in matched pairs......
It is a little worrying that your memory is IBM type, as this can be a little specialised.
"Buy" the new memory only on the understanding that if it does not work in your PC that you can get a refund.
What speed is the existing CPU 25/33/60/100 MHZ ?
If you inspect the motherboard, it might inform you, via jumper settings, what other CPU's can be installed. A 25 board will often accept a 33MHz, and a 60 board will often accept a 100MHz chip.
PS - I have got a 486 33MHz chip and a DX4 100MHz chip gathering dust - cost - just pay the postage....... I have an overclocking chip but I can't put my hands on it.
And I still use my trusty 486 - 100MHz computer for software testing running windows 95, and it is bombproof.
my pc is a 486 75mhz pc and it says on the ram 4mb and it displys on the screen 8mb of ram and there is only one ram stick i need to upgrage the chip to about 233mhz will mp pb450 board handle it or should i get a new board
It is pointless trying to upgrade a 486, just a waste of time and money. If it is good enough for typing letters or whatever you use it for, fine. Keep on using it with that old software until it grinds to a halt. If it is not good enough, then buy a brand new system or at least a new base unit.
You only need to spend a few hundred pounds if you shop around. The performance benefits will be a quantum leap for you. Nowadays, one needs at least 128 Mbytes RAM, DVD, CD-RW, USB ports, 40 Gbyte hard drive and Windows XP or 2000.