Phase 5 and the Blizzard PPCs

[darksun9210]

the 128Mb limit wasn't phase5's fault.

the A4k was designed when 4Mb simms were expensive, and the cost of 32Mb simms was positivly discouraging.... i think at the time a 32Mb simm cost 250UKP+

so the address space of the A4000 was designed so that only 128Mb of ram was available to the CPU slot. mainly due to address space having to be allocated to Zorro3 addressing. as having 128Mb of ram at that time was nie on inconcievable. (yeah i can't spell). this wan't seen as too much of a problem.
 
however, you can add up to 512Mb per zorro3 slot. just you won't be able to run any OS that can't handle split memory areas (i.e. linux Apus) to take advantage of the extra ram.

anyway, the A1200 didn't have this Zorro3 'burden' and has all its addressing free for other use.

thinking about it, the A1200 roms don't carry the code to initialize the Z3 address space, so if you put the 1200 roms into an A4000, will you loose Z3 functionality but gain shed loads of CPU ram address space?

[darksun9210]

probably, but if you want to use a mediator, or prommy PCI bus, then you'd somehow have to force the zorro devices to map into the upper bounderies of the zorro space, other wise they would *conflict* (gasp! a PC word for hardware installation used in reference with an amiga) with any extra ram you have above 128Mb on the cyberstorm.

i'm not sure how funky the autoconfig is in relation to sorting this little mess out

maybe if the cybertorm could be "reflashed" (dont ask me how to show itself as two "zorro3" devices maybe... one CPU device and one memory device.. each taking a 512Mb address range, then this would leave the lower 1Gb of zorro space free, and autoconfig would map the true zorro devices above it. as far as i can figure out. and the cyberstorm (memory interface permitting) could then as part of the "reflash" (if you can modify that in the code) you could say allow 512Mb ram (4x 128Mb simms - and have it suck even more current from your PSU

most of what i am saying is an educated guess given expirience and going over the memory layouts, hardware topologies, etc etc. and should not be taken as gospel. if i'm wrong anywhere please correct me.

i don't even know if it is possible to reflash the cyberstorm to change its memory addressing. or the way it presents itself to the amiga on initialization. it may be that you can change the flashrom addressing, but can't change the way it appears to the amiga due to the cpu hardwired glue logic on the card. so you are stuck with it being a 128Kb zorro3 card. i can't help but think that there would be some serious hardware reprogramming involved with regard to the logic chips. but i may be wrong...

(don't you just hate thinking of the answers for questions you're typing as you are typing the questions?)