jph@eagle.UUCP (J.P.Haggerty) (09/05/85)
Does anyone know how the Amiga does multiprogramming safely without a memory-management unit? The Byte article makes no mention of MMU hardware. Joe Haggerty, AT&T Bell Laboratories, Summit, NJ
mroddy@enmasse.UUCP (Mark Roddy) (09/06/85)
> Does anyone know how the Amiga does multiprogramming > safely without a memory-management unit? The Byte article > makes no mention of MMU hardware. There isn't one, so it doesn't do it safely, although the Amiga loyalists are kind of blind about this point. I think that when you boot up a couple of different software packages, all of them doing their own thing all over absolute address space, you have a fairly severe problem. Especially if, as has been the case with every other PC, third party software developers take liberties with the OS and its entry points. -- Mark Roddy Net working, Just reading the news. (harvard!talcott!panda!enmasse!mroddy)
john@anasazi.UUCP (John Moore) (09/12/85)
In article <462@enmasse.UUCP> mroddy@enmasse.UUCP (Mark Roddy) writes: >> Does anyone know how the Amiga does multiprogramming >> safely without a memory-management unit? The Byte article >> makes no mention of MMU hardware. > >There isn't one, so it doesn't do it safely, although the Amiga loyalists >are kind of blind about this point. I think that when you boot up a > (harvard!talcott!panda!enmasse!mroddy) I have heard (from someone looking under the hood) that the Atari 520ST has a chip labelled "MMU". Is this an MMU? Is it any good? If so, this would seem to be a significant advantage for the ST. -- John Moore (NJ7E) {decvax|ihnp4|hao}!noao!terak!anasazi!john {hao!noao|decvax|ihnp4|seismo}!terak!anasazi!john (602) 952-8205 (day or evening)
rb@ccivax.UUCP (rex ballard) (09/20/85)
> In article <462@enmasse.UUCP> mroddy@enmasse.UUCP (Mark Roddy) writes: > >> Does anyone know how the Amiga does multiprogramming > >> safely without a memory-management unit? The Byte article > >> makes no mention of MMU hardware. Looks like they may be using OS-9's 'no mmu' trick of making all code relocatable through the compiler. Looks like the only safe place is WCS. (OS-9 has a protected MMU option). > >There isn't one, so it doesn't do it safely, although the Amiga loyalists > >are kind of blind about this point. I think that when you boot up a > > (harvard!talcott!panda!enmasse!mroddy) > I have heard (from someone looking under the hood) that the Atari 520ST > has a chip labelled "MMU". Is this an MMU? Is it any good? If so, this ^^^ > would seem to be a significant advantage for the ST. An old Dvorak column indicated that Atari was working on at least TWO OS's, the CP/M-68k, and a multi-tasking one. Since CP/M doesn't need MMU support, there would be no documentation of it. If 'concurrent' was the other system and just took too long, then considering the Insistance of DRI that the AT provide priveledged memory protection and MMU, there would be even stronger need (and capability) for it in the ST. "Presenting the ATARI ST" has a memory map on page 34 that show address $FF8000-$FF8200 labled "DATA CONFIGURATION", in the I/O region. If that ain't an MMU term, what is? (Interesting 512 bytes - 512K hmmm), if they send you a 68010 with your next OS, watch out!!!. Anybody look at those addresses? If this is the case, does that mean that the 512K in the machine is really the CACHE for an external RAM disk? I've been looking at what is available in SCSI devices lately, seems IOMEGA makes a BOURNELLI BOX for it. Others items included an 80MB disk drive ($1000 Q 5000, no enclosure), a couple of 8" drives, and a few of the little drives. Isn't that also the usual MAC hard disk interface? What is SCSI (Small Computer Standard Interface)? Is it some sort of super-fast GPIB? I noticed one of the functions was some sort of "find pattern" command. What are some of the others? (If there are a lot, a few examples would be nice). I noticed that 1.33Mbytes/sec is about 10Mbit/sec, anybody know of an Ethernet to SCSI interface? Does AMIGA have an SCSI interface? (I saw one SCSI controller card for IBM). Are HPIB and SCSI commands mutually exclusive? Are the busses similar? While we are being technical: 'Presenting...' describes the BIOS vectors and the BDOS vectors, where is VDI? Is it a 'trap vector', a 'run-time library', or a 'link-time library'? Are the TOS vectors any better than the BDOS vectors (Seek sequential, Flush, buffering...), are BIOS vectors still available? Does VDI use the Graphics chip to do the painting, or does it 'bit bump' like the MAC? What's the top speed on the 68901 (rs232 port)? Do the sync pins (RxC,TxC) go anywhere? What are some of the GPU operations? How do they compare with the NEC 7220?