S0lll0s wrote:Zardoz wrote:The BIOS can't be load from a disk !!! The BIOS is a little program that is burned in a ROM chip, can't be updated or uploaded. If you like to replace it, you must replace the entire chip.
Yeah, and I propose that the BIOS is on a ROM chip that can be flashed (like any IRL chip) using a lot of cost
You mean that the BIOS being a EEPROM allowing to upgrade (or overwrite and replaced by malicious software). Could be... I personally like more of flashing the chip with the computer power off, like if were unpluged put in a EEPROM burner, rewrite and pluged in the machine..
S0lll0s wrote:And instead of expanding the DCPU spec unreasonably (i.e. by introducing a PC that does not point to the memory) I suggest that instead of executing the ROM "directly" it is copied into the beginning of the RAM on poweron and then executed just like anything else.
If this was not the case we would need an extra instruction (or at least an extra flag) to tell the DCPU to switch to "regular memory" when the BIOS is done.
It is called "Shadow BIOS" in some old PCs. It was speed-up trick because these ROM/EPROM of these time was too slow compared to the CPU bus, and copying ROM data to RAM allow to speed up software that needs to use the BIOS routines. In our case this speed-up is unnecessary. The only reason that I can find to be necessary, is in the case of the DCPU-16 as a alternative to bank switching. as allow to reuse these space address. But in the case of the RC3200 not have any sense... you have a lot of address space.
You not need "extra instruction" to handle ROM. Simply, a range of address are Write only. This means that if a computer program try to write at these address, nothing will happen. This you could see in RC3200-VM were you have a 64KiB ROM + 128KiB RAM, and if you try to write over the 64KiB ROM, simply does nothing, like in a real machine.