Date: Fri, 8 Oct 1999 18:32:10 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: doconnor@gsoft.com.au (Daniel O'Connor) Cc: tlambert@primenet.com, chat@FreeBSD.ORG, kris@airnet.net, andrews@TECHNOLOGIST.COM, gryph@mindless.com, narvi@haldjas.folklore.ee Subject: Re: Porting FreeBSD to the Mac (68K or PPC) Message-ID: <199910081832.LAA07829@usr07.primenet.com> In-Reply-To: <XFMail.991008095118.doconnor@gsoft.com.au> from "Daniel O'Connor" at Oct 8, 99 09:51:18 am
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> On 07-Oct-99 Terry Lambert wrote: > > > All the embedded 68xxx processors are made up of: > > > a) ordinary 680x0 core > > > b) internal bus > > > c) a number of peripherials > > > > I think the question was about whether or not it could support > > paged virtual memory, i.e. does it have an MMU. > > > > I think the answer is "yes", because of the "3". > > Well providing it isn't an 030EC core.. http://www.mot-sps.com/products/microprocessors/32_bit/mc68ez328.html 8-(. It's an EZ, since it can handle more than 2M of DRAM. But it has "Programmable Memory Access", which is apparently Motorolla's way of disguising the fact that it doesn't have an MMU. The Palm Pilot itself may include an MMU. The processor supports supervisor mode based memory block protection. THis could be abused as if the chip were an Alpha, MIPS, or 386 (which doesn't support write protect in supervisor mode) to implement paged memory management in software, I think, but you'd be faulting a lot in order to handle and restart the request in user mode code. 8-(. I also couldn't find out whether or not MOPSW (move processor status word) was a protected instruction in user m0ode or not. If not (it isn't on the vanilla MC68000), then the hardware would be incapable of supporting a real virtual machine, as the original Amiga's can attest. It looks like the Palm Linux guys, if they are doing anything, are running with SVR3.2/x86 Xenix 2.x non-paged memory management, if they are running at all, unless I'm really missing the boat. 8-(. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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