I have done the ram upgrade on my xbox a couple of years ago but I never softmodded it.
That said, this is what you have to bear in mind whether soft modded or not:
The ONLY things that can make use of the 128MB is:
1) mame emulators (MameoX, mameX etc ect)
2) Linux (ONLY if booted from a Cromwell bios) if using Xbeboot it won't notice the extra.
3) Xbox Media Centre
I suspect that seeing as it is the Xbox that is aware of the extra 64MB rather than the bios (I never needed a custom bios to see the extra 64MB for emulators / xbmc) that however you load it ie softmod / hardmod that XBMC and Mame will see it and use it correctly.
So based on that, are you sure you still wanna do the upgrade, if you aren't using linux I really really wouldn't bother.
XBMC doesn't run noticeably faster, (I have a 128MB Xbox and a 64MB, the visualisations are the same on each), And newer versions of MameX have support for virtual memory so even 64MB Xboxes can load larger roms.
Xbox games will take absolutely no notice you have an extra 64mb so don't kid yourself that Halo2 will run any faster cos it won't! Although if you wanna reduce load times from games on HD do the ATA66 mod (it really is the ATA66 mod despite what people call it as it was ATA66 that defined the standard for the 80 conductor 40 pin IDE Cable).
This noticeably cuts down load times in most cases by a third, and sometimes only a quarter.
Also don't bother with the Xbox Ram Delimeter XBE utility, In my experience it makes no difference whatsoever if the code itself isn't aware of the extra 64MB.
To expressley answer your question then yes it will boot as bios that are unaware of the extra such as the stock MS BIOS still boot the 128MB xbox I have with the modchip turned off, with it on and using XBMC as dash (Which I do) then XBMC will see the extra 64MB.
I must admit that I think you are missing out on lots of cool features without a modchip but hey you are comfortable without! That said if you haven't installed a modchip I doubt that your soldering skills or tools are upto the job of soldering in 4 50pin SMD memory chips - no offence intended, but it is a right bast*** of a job. If you don't have a decent multimeter (Definately want a digital one for ease of use) a magnifying glass, desoldering braid, very fine tipped iron and plenty of patience then I'd get someone else to do it.
I'd offer to do it for you but I'm the other side of the pond from you (about 4750 miles the other side) in the UK and there is a problem with finding places that sell the chips and will deliver to the UK (Stegen electronics in Holland does but you can only pay by bank transfer which is 20 dollars for a 40 dollar transfer).
Edited by nickb834, 23 January 2006 - 05:23 PM.