Don't forget the ROM has a slower connection to the system than RAM does. It depends on the motherboard but the RAM usually has […]
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Don't forget the ROM has a slower connection to the system than RAM does. It depends on the motherboard but the RAM usually has a direct connection to the CPU, while the ROM goes over a slower channel like the ISA bus.
Thanx for the information, and that's what I was afraid for that the BIOS is connected via a slower way.
But A 386 computer has everything over the ISA bus ? ( Neumann architecture )
Maybe RAM is direct connected the the CPU and the rest over the ISA bus.
If you have a memory expansion card on the ISA bus then it might run at the same speed as a fast ROM chip so you'd get no benefit from shadowing. Also remember that on top of the slower connection, ROM chips usually read one byte per cycle while RAM can read up to eight bytes per cycle depending on architecture (30-pin RAM is also one-byte, but 72-pin is 4-byte and paired 72-pin like in Pentiums is 8-bytes/cycle.)
I see you're completly right.
It's always worth testing, but I think in this case there won't be much of an improvement for most cases, unless you find a particularly unusual motherboard with the ROM wired up differently.