I suspect you are thinking of the prefix instructions used in the block move. Or maybe you didn't notice that you can use the prefix instruction. In any case the block move on Intel is about the same as a move character on the mainframe.
In the 8086 days it took several clock cycles to do anything. The most annoying to me was the 60 cycle divide instruction. These days they are much faster, some instructions being only one clock. The only operations that I know of that take more instructions on Intel are decimal arithmetic, which are really bad on Intel. -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] Behalf Of Richard Pinion Sent: Thursday, May 18, 2006 7:05 AM To: LINUX-390@VM.MARIST.EDU Subject: Re: Fw: [LINUX-390] Who's been reading our list... I've always wanted to ask this question and you seem like someone who would know. First and foremost I am not a computer engineer! Here's the situation. When the PC first came out I taught myself some basic assembler for the x86 chip. One thing that I remember to move 255 bytes from one location to another I had to set up a count register, source register, and target register. The move instruction was executed in a loop that decemented/incremented (I don't remember which) the counter. While I'm sure there is a lot of stuff that happens at the microcode level of the mainframe, we use one assembler instruction to move 255 bytes. From what I remember of x86 assembler it took more instructions to do things than it did on the mainframe. If the the x86 chip were faster than the mainframe's chip, would some of that speed be lost because it takes more instructions to do the same task? Please be kind in responding. Like I said this stuff is really over my head! >>> [EMAIL PROTECTED] 5/18/2006 9:51:12 AM >>> Yes tagging works, but you will find that the system z holds a lot more translations in a two tiered TLB and has tagging as well. Thus the System z does not have to retranslate as often. Joe Temple Distinguished Engineer Sr. Certified IT Specialist [EMAIL PROTECTED] 845-435-6301 295/6301 cell 914-706-5211 Home office 845-338-1448 Home 845-338-8794 Alan Cox <[EMAIL PROTECTED] u.org.uk> To Sent by: Linux on LINUX-390@VM.MARIST.EDU 390 Port cc <[EMAIL PROTECTED] IST.EDU> Subject Re: Fw: [LINUX-390] Who's been reading our list... 05/18/2006 07:23 AM Please respond to Linux on 390 Port <[EMAIL PROTECTED] IST.EDU> On Iau, 2006-05-18 at 10:03 +0200, Martin Schwidefsky wrote: > On x86 it is the translation-lookaside-buffers (TLBs) which get flushed > each time the control register 1 is loaded. Switching between threads is [%cr3 not 1 but thats by the way] > fine because the use the same translation table. Switching between > processes has a performance penalty. On mainframes the TLBs are not > flushed for any context switch. Not on a current AMD x86 processor. The opteron and AMD64 processor line uses tags on the tlb entries so that it can avoid this without the underlying OS being changed. > The cache is a different story. Mainframes have the advantage of a > shared level 2 cache compared to x86. If a process migrates from one > processor to another, the cache lines of the process just have to be > loaded from level 2 cache to level 1 cache again before they can be > accessed. On x86 it goes over memory. Long ago yes but even with private L2 caches (which have advantages too) you can send lines from cache to cache directly if your bus protocol is sane. Alan ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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
