386SX Addressing Range

[srg]

Hi

Accoring to The Indespensable PC Hardware Boot 4 the 386 SX only has a physical address space of 16MB, because of its 16-bit bus.

Is this a miss print? If not, does this mean that it can only use 16MB RAM even with flat addressing and paging on?

[Schol-R-LEA]

This is correct, but it only refers to physical memory addressing. It is not so much the 16 bit addressing that is at fault, but that (like the 286) it only had 24 address lines total. Using paged virtual memory, the 386sx could use the exact same addressing as the 386dx, but had to map that virtual memory to the 16M of physical RAM it could address, and thus was more likely to suffer page faults.

Comments and corrections welcome.

[srg]

ahh ic

yeah 24 addressing lines, sorry hehe :-[