23 Nov
2006
23 Nov
'06
12:59 p.m.
On 23 Nov 2006 at 14:01, Tothwolf wrote:
Actually, the early 486SX dies were fully working
486DX parts. They just
had a different pinout and no bond wires were installed for the FPU. Intel
did ship later 486SX chips that were made from dies with defective FPUs.
As I understand it, Intel on the early -20 486s had a yield problem
with the FPU circuitry. So the 486sx was born. NMI* was moved from
B15 to A15 and and FERR* and IGNNE* weren't bonded out. Later 486s
(the -25 and -33) had no NDP on the die.
The 487 has the same pinout as the 486DX with the exception of
bringing MP* out to B14 (nc on the 486SX) and FERR* out to A13. As I
understand it, the 487sx was essentially a fully-functional 486DX
under the clay.
Cheers,
Chuck