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[s_jo03]

I'm all ready to flash a 1.1 tsop, preferable with 4x 256M bioses.  However, I came across
http://xbox-linux.sourceforge.net/docs/tso...psplitting.html

What he is saying makes sence, but I'm confused about all the success reports in the forum ?

[Scan-C]

the 4 way split is unsafe. many people had problems because only certain bios verison will work. best is to split the tsop 2x512 kb and you can use any bios you like.

[Exobex]

Splitting should be fine as long as you use SPDT switches (that switch A18 and/or A19 not just to ground, but between Vcc and ground.

On most switches, A18 or A19 go to the middle pin, Vcc goes to one side, ground goes to the other.

If you don't do it this way, what you get is:-
A18 switch off, A19 switch off = 1MB BIOS
A18 switch on, A19 switch off = 512KB BIOS (bank 0+2)
A18 switch off, A19 switch on = 512KB BIOS (bank 0+1)
A18 switch on, A19 switch on = 256KB BIOS (bank 0)
where "on" = grounded and "off" = not grounded

If you do it with SPDT switches, what you get is:-
A18 switch off, A19 switch off = 256KB BIOS (bank 0)
A18 switch on, A19 switch off = 256KB BIOS (bank 1)
A18 switch off, A19 switch on = 256KB BIOS (bank 2)
A18 switch on, A19 switch on = 256KB BIOS (bank 3)
where "on" = Vcc and "off" = grounded

If you use SPDT switches that have a "centre-off" position, you get:-
A18 switch off, A19 switch off = 256KB BIOS (bank 0)
A18 switch mid, A19 switch off = 512KB BIOS (bank 0+1)
A18 switch on, A19 switch off = 256KB BIOS (bank 1)
A18 switch off, A19 switch on = 256KB BIOS (bank 2)
A18 switch mid, A19 switch on = 512KB BIOS (bank 2+3)
A18 switch on, A19 switch on = 256KB BIOS (bank 3)
A18 switch off, A19 switch mid = 512KB BIOS (bank 0+2)
A18 switch mid, A19 switch mid = 1MB BIOS (bank 0+1+2+3)
A18 switch on, A19 switch mid = 512KB BIOS (bank 1+3)where "on" = Vcc and "off" = grounded


This post has been edited by Exobex: Dec 19 2003, 01:06 PM

[B1ff]

To which they say:

QUOTE

It was suggested to connect A18 and A19 resp. either to GND or to Vcc, to have definitive 1s and 0s, but we cannot recommand this either, because it is quite likely that this will make your MCPX explode! Because of the open collector logic, connecting a pin to Vcc means that you shorten Vcc and GND, which, in the best case, will break the transistor in the MCPX that switches the address line (so that you cannot access more than 256 KB of flash afterwards), and in the worst case, it will break the whole MCPX. This will not be the case if you cut the A18 and A19 pins, but many people broke their Xboxes this way, so better don't do it.

Anyway, I've had one of those vcc/ground switches on A19 for a while to switch between two 512KB images with retail and an X2 multi-BIOS, and my MCPX hasn't exploded yet.

[52volts]

I say its not safe!!!!

I've flashed 5 xbox for myself and friends. Today the 1.0 Xbox that I flshed failed. The bios was retail+retail+x2+x2 and I used the vcc and ground with the SPDT switch. Now I get jumpy images and no more color!!! However I still have 3 1.1 xboxs that are setup the same way that still works. So you decide if its safe enough for you.

[wtsexton]

QUOTE (52volts @ Dec 20 2003, 05:33 AM)

I say its not safe!!!! I've flashed 5 xbox for myself and friends. Today the 1.0 Xbox that I flshed failed. The bios was retail+retail+x2+x2 and I used the vcc and ground with the SPDT switch. Now I get jumpy images and no more color!!! However I still have 3 1.1 xboxs that are setup the same way that still works. So you decide if its safe enough for you.

Got me my 1.1 has been split into 2 banks for seven months now no issues.