From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <392E4B8B.E3C70B27@agelectronics.co.uk> Date: Fri, 26 May 2000 11:01:47 +0100 From: Adrian Cox MIME-Version: 1.0 To: linuxppc-embedded@lists.linuxppc.org Subject: Re: Floating Point problems with Linux on the EST SBC8260 References: Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Geir Frode Raanes wrote: > BTW, VxWorks can not easily handle more than 32 MBytes of local RAM > as the eabi specification (as a result of the PowerPC architecure) > rules for 26 bit (signed) relative addressing. Hence, I will design > in exactly 32 MBytes of soldered low power SDRAM on UPMA and assign > UPMB to a DIMM socket. How does PPC/Linux handle this addressing > problem? The current release of VxWorks is prepared to use a long jump sequence to jump to a 32 bit address. Tornado 2 out of the box has worked fine for me on a 128MByte 7400. The problem only ever occurs when your code occupies an address range greater than 32MBytes. VxWorks doesn't support virtual addressing without some add-ons. It always placed the kernel at the bottom of memory and dynamically loaded code at the top, so that calls from the dynamically loaded code into the kernel had offsets that couldn't fit in a relative branch. Linux, however, never had this problem. Linux uses virtual memory, which keeps the application within a smaller address range. - Adrian Cox, AG Electronics ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/