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From: "Andy "Krazy" Glew" on 18 Apr 2010 14:25 On 4/18/2010 4:57 AM, Niels J�rgen Kruse wrote: > Andy "Krazy" Glew<ag-news(a)patten-glew.net> wrote: > >> The ARM Cortex A9 CPU is out-of-order, and is becoming more and more >> widely used in things like cell phones and iPads. > > Cortex A9 is not shipping in any product yet (I believe). Lots of > preannouncements though. The Apple A4 CPU is currently believed to be a > tweaked Cortex A8, perhaps related to the tweaked A8 that Intrinsity did > for Samsung before being acquired by Apple. Ref? Most of the articles that I have seen say that the iPad A4 is a Cortex A9. One conspiracy-theorist type seems to think that it might actually be the PA Semi OOO PowerPC, running an ARM emulator.
From: MitchAlsup on 18 Apr 2010 15:06 On Apr 18, 1:15 pm, "Andy \"Krazy\" Glew" <ag-n...(a)patten-glew.net> wrote: > System code tends to have unpredictable branches, which hurt many OOO machines. I think it is easier to think that system codes have so much inherent serializations that the efforts applied in doing OoO are "for want" and that these great big OoO machines degrade down to just about the same performance as the absolutely in-order cousins. Its a far bigger issue than simple branch mispredictability. Pointer chasing into poorly cached data structures is rampant; "dangerous" instructions that are inherently serialized; and poor TLB translation success rates. Overall, there just is not that much ILP left in many of the paths through system codes. Mitch
From: Terje Mathisen "terje.mathisen at on 18 Apr 2010 15:42 nmm1(a)cam.ac.uk wrote: > Well, yes, but that's no different from any other choice. As I have > posted before, I favour a heterogeneous design on-chip: > > Essentially uninteruptible, user-mode only, out-of-order CPUs > for applications etc. > Interuptible, system-mode capable, in-order CPUs for the kernel > and its daemons. This forces the OS to effectively become a message-passing system, since every single os call would otherwise require a pair of migrations between the two types of cpus. I'm not saying this would be bad though, since actual data could still be passed as pointers... Terje -- - <Terje.Mathisen at tmsw.no> "almost all programming can be viewed as an exercise in caching"
From: =?ISO-8859-1?Q?Niels_J=F8rgen_Kruse?= on 18 Apr 2010 15:49 Andy "Krazy" Glew <ag-news(a)patten-glew.net> wrote: > On 4/18/2010 4:57 AM, Niels J�rgen Kruse wrote: > > Andy "Krazy" Glew<ag-news(a)patten-glew.net> wrote: > > > >> The ARM Cortex A9 CPU is out-of-order, and is becoming more and more > >> widely used in things like cell phones and iPads. > > > > Cortex A9 is not shipping in any product yet (I believe). Lots of > > preannouncements though. The Apple A4 CPU is currently believed to be a > > tweaked Cortex A8, perhaps related to the tweaked A8 that Intrinsity did > > for Samsung before being acquired by Apple. > > Ref? > > Most of the articles that I have seen say that the iPad A4 is a Cortex A9. That would have been the early speculation. A more current view is <http://www.anandtech.com/show/3640/apples-ipad-the-anandtech-review/16> and the next page with benchmarks. The A4 is about half the speed of an Atom N450 (512K Cache, 1.66 GHz) on a web page load benchmark. The hype around the Cortex A9 would lead us to expect better. -- Mvh./Regards, Niels J�rgen Kruse, Vanl�se, Denmark
From: Muzaffer Kal on 18 Apr 2010 15:56
On Sun, 18 Apr 2010 11:25:38 -0700, "Andy \"Krazy\" Glew" <ag-news(a)patten-glew.net> wrote: >On 4/18/2010 4:57 AM, Niels J�rgen Kruse wrote: >> Andy "Krazy" Glew<ag-news(a)patten-glew.net> wrote: >> >>> The ARM Cortex A9 CPU is out-of-order, and is becoming more and more >>> widely used in things like cell phones and iPads. >> >> Cortex A9 is not shipping in any product yet (I believe). Lots of >> preannouncements though. The Apple A4 CPU is currently believed to be a >> tweaked Cortex A8, perhaps related to the tweaked A8 that Intrinsity did >> for Samsung before being acquired by Apple. > >Ref? > >Most of the articles that I have seen say that the iPad A4 is a Cortex A9. Based on my count of google results, A8 is slightly ahead of A9 in terms of what core is actually in A4. -- Muzaffer Kal DSPIA INC. ASIC/FPGA Design Services http://www.dspia.com |