bdb@cl.cam.ac.uk (Brian Brunswick) (03/28/90)
The response that I got from my original query about whether I should put the mac emulator that I have produced into some kind of free distribution has generally been interesting. The general consensus seems to be that AMAX copies the mac roms into ram, and so it is probably legal for me to do the same. I will therefore proceed to produce what I hope will be an early beta test version, and then send it to some of the numerous people who volunteered for this - thanks very much! This version will have protection style techniques in it to try and enforce its use with hardware - ie it will check in nefarious places for the presence of the mac roms at some fixed address that I have yet to designate - any good suggestions? Please don't expect any replies for the next two weeks though, as I am going down, and leaving my beloved amiga behind. In answer to some of the questions asked: Do I have any way of transfering data from mac disks - like the AMAX middle few tracks technique? No. I initially got data across by serial transfer - of entire disk images. Now, I plug my amiga scsi drive into a mac, and write data onto the mac partition of it. Can it use the 68000, as most amiga owners have this? Yes, but only if you have 4MB of expansion memory, or memory that can be wangled to give 128k at 0x400000 and a decent amount below this. So far, I need to have the roms at their original 4MB base address, since, although the roms themselves are relocateable, the patches that are applied by the mac system as it starts up are not. With a 68010 or greater, one can fake it by generating an address error at 4MB, and relocating all references. I'm not too sure that this worries me anyway - If one is building a bit of hardware, the trivial upgrade to a 68010 is easy, and <L10 anyway. So anyway, to hopefully quote Fu Man Chu, THE WORLD WILL HERE FROM ME AGAIN! And to the person who wanted me to email them the mac roms - no chance! Brian Brunswick, bdb@uk.ac.cam.cl, bdb10@uk.ac.cam.phx. Short .sig rules!
cs121jj@ux1.cso.uiuc.edu (03/30/90)
/* Written 6:47 am Mar 28, 1990 by bdb@cl.cam.ac.uk in ux1.cso.uiuc.edu:comp.sys.amiga.tech */ /* ---------- "A PD mac emulator - summary" ---------- */ Do I have any way of transfering data from mac disks - like the AMAX middle few tracks technique? No. I initially got data across by serial transfer - of entire disk images. Now, I plug my amiga scsi drive into a mac, and write data onto the mac partition of it. /* End of text from ux1.cso.uiuc.edu:comp.sys.amiga.tech */ I was wondering why one could not use this idea to read mac disks on an Amiga drive... Since the Mac drives have adjustible spin rates on the drive motors, that would lead me to believe that all the circular tracks on the disk have the same number of sectors, but are different sizes. So why not read the far and near tracks (the tracks that are NOT the "middle" tracks that both Mac and Amiga can read on those AMAX-Mini-Transfer disks) by getting consecutive sectors on consecutive passes of the drive? By this I mean, to get sectors A-Z, first get A, any way you want to, then wait for the disk to spin 1 complete revolution PLUS 1 sector and then read THAT sector (sector B, as I call it in this note). Do the same thing over again to get sectors C-Z. And on the longer tracks located physically on the tracks that are greater in diameter (the previous description was for the tracks that are the shortest in diameter) , just use the same idea, except you may need to make more than 1 pass for each sector (since it is physically longer, the data will be "stretched out" across the sector because each sector can only hold X bytes of data [X= a fixed number]). This idea will result in slower reads on data located non-centrally, but at least it'll save all of us not having to buy a Mac drive! (But if we did get a Mac drive, couldn't we use THAT drive ALL the time? For BOTH Amiga & Mac, since the Mac drive can adjust the speed and the Amiga drive cannot??) Let me know if this is a good idea...if you like it and use it, give me some credit for it, because (as far as I know), nobody but me uses this at all. ------------------------------------------------------------------------------ Jeff Nicholson jeffo@mrcnext.cso.uiuc.edu Amiga + '030 = POWER!!! ------------------------------------------------------------------------------