Some explanation on the way memory banks work on the X2 chips...
When looking at banks in the X2 BIOS Manager PC app or the FlashX XBE you'll see 4 banks listed. But on the X2 switch bank you've only got a bank1/bank2 switch... so what gives?
The skinny is this. The X2 has a 1MB chip. This is divided into 2 512KB banks. These two banks are what is selectable via the switch. A fresh X2 includes FlashBIOS 3.01 on bank1 and 3.03 on bank2, IIRC. Why the 4 banks in X2BM and FlashX? The BIOS files commonly used in Xbox modding start out at the 256KB size. (I don't think anyone has created anything smaller...) To simplify the construction of the X2 it was designed to only have two selectable banks, plenty for your average modder. Check out an X3 and you'll see that you can select from up to 8 256KB banks (2MB chip), but this is also a more complex chip. The 4 256KB banks on the X2 are there to provide slots for the BIOSes of that size, but the read points you can select from (switch bank1/2) are at the 0 and 512KB markers, or banks 1 and 3 in X2BM/FlashX. If you're using a 256KB BIOS you really aren't using banks 2 and 4. They sort of just act as filler when using 256KB BIOSes. Ok, then why have that extra space there? This forsight allows us to use 512KB BIOSes that take up two of those slots, like the recent X2CL 5xxx series. And the 1MB total size of the chip allows us to have two of them on there, or any two BIOSes up to 512KB each. You can have the 512KB 5035 in switch bank 1 and the 256KB FlashBIOS 3.03 in switch bank 2.
Sometimes for people new to working with this sort of stuff this can get confusing. The easy way to sort it out is to just remember that the bank selection switch doesn't select the logical 256KB bank, but the read point in 512KB increments. I don't remember if a full 1MB BIOS would be supported on an X2.
Take all this at face value. All of this has been off the top of my head, calling on what I remember about the details and what experiences I've had with the chip. I think I've got it right but offer no guarentees. If I'm wrong anywhere I'd be interested to know what is correct, for my own better understanding.
-Whoopin'
