The DMA limit depends on the hardware. On 32 bit Intel DMA is limited to 16M. On 64 bit Intel there is no limit. On Z the DMA limit is 2G.
Note: the ISA bus isn't really the problem. The problem is that the DMA chip only addresses 24 bits, although this is because the ISA bus was 24 bit. -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] Behalf Of John Summerfield Sent: Saturday, April 26, 2008 8:04 PM To: [email protected] Subject: Re: questions regarding /proc/buddyinfo Rob van der Heij wrote: > On Thu, Apr 24, 2008 at 7:05 PM, Michael O'Reilly <[EMAIL PROTECTED]> wrote: > >> Because the System Z architecture doesn't have these two limitations, it >> doesn't support ISA cards and it is a 64-bit architecture, you only need >> one zone. > > Beg to differ. We use that to separate under 2GB and above 2GB because > some things in live need to happen under the Bar (like channel > programs). So when all is under the Bar (vmsize < 2G) you just have > one zone. Michael made me do it. I'm running Sl5 (RHEL-clone 5) on two systems here, one 32-bit PC and the other 64-bit PC. Additionally I have Fedora 9-beta on a 64-bit PC. SL5, 32-bit (1 Gb RAM) has DMA and HighMem. SL5, 64-bit (5 Gb RAM) has DMA. Beats me, haven't seen an ISA bus since P III. F9-beta 64-bit (2 Gbyte RAM) has DMA and DMA-32. The 64-bit systems are HP DC7700s, the only significant difference I know about is the CPUs, AFAIK the mobos are identical. Just to be clear, the system with most RAM has one zone. -- Cheers John -- spambait [EMAIL PROTECTED] [EMAIL PROTECTED] -- Advice http://webfoot.com/advice/email.top.php http://www.catb.org/~esr/faqs/smart-questions.html http://support.microsoft.com/kb/555375 You cannot reply off-list:-) ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 __________________________________________________________________________________________________ CONFIDENTIALITY NOTICE: This email from the State of California is for the sole use of the intended recipient and may contain confidential and privileged information. Any unauthorized review or use, including disclosure or distribution, is prohibited. If you are not the intended recipient, please contact the sender and destroy all copies of this email.
