Hi poc, Markku. I think I have what I wanted. Thanks for taking the time. On Wed, 2009-09-30 at 12:02 -0430, Patrick O'Callaghan wrote: > On Wed, 2009-09-30 at 12:03 -0400, William Case wrote: > > Thanks poc; > > > > Then what was Markku referring to when he said "A typical 64-bit DIMM > > "stick" has eight 8-bit wide chips." The chip is one of the minute > > black chips I can just barely see on a RAM stick --? That is what I > > originally thought. > > Yes. > > > Markku's statement then implies that a 64 bit qword is stored in an 8 x > > 8 array of cells. True? > > No. If a 64-bit wide DIMM has 8 chips on it you can be highly confident > in saying the chips are 8 bits wide, but their depth is another matter. > And the fact that the chip presents an 8-bit wide interface doesn't mean > that the internal organization is in 8x8 bit arrays, though it might be. > > Furthermore, the 64 bits in a word will pretty much *never* be stored in > a single 8x8 array. They'll be stored in a number of parallel arrays for > speed of access, usually across 8 separate chips. > Ah, back to 8 + 8 + 8 + 8 + 8 + 8 + 8 + 8 cells arranged side-by-side in a line on an individual DIMM/DRAM stick. OK, that's good enough for the personal visualization I wanted. I understand that this can vary, but once one has a basic configuration in mind, it only requires mild mental gymnastics to move the parts and pieces around in one's head as long as the parts and pieces are still all there, > Again: this level of detail (the array size) is essentially invisible to > the programmer. I know. My objective is not primarily for programming but for understanding how a machine (basically an appliance) plugged into a wall socket can do so much. > > > By the Way: > > The definition of a 'word' seems to be all over the place. > > > > With Intel, the definition I have read says a 'word' is 16 bits, a > > 'double word (dword)' is 32 bits, and a 'quadruple word (qword)' is 64 > > bits. > > That's true of Intel. It's not necessarily true across all computer > architectures (in fact it isn't, as I mentioned in my previous reply). > > > The specs for the 64 bit AMD CPU I used to have defined a 'word' as > > whatever the machine said it was. In my case at the time, a 'word' > > would have been 64 bits. ???? > > A word is normally considered to be the unit of the bus cycle of the > machine (but see the above discussion of dual-cycle implementations) and > coincides with the maximum addressable range of virtual memory (physical > memory can be less, or even more in some cases). It usually also > coincides with the size of the most common machine instructions, those > these can also vary depending on the architecture. > > Good introductions to this stuff are Hennessy and Patterson, or > Tanenbaum's Computer Organization book. I have both books and read them a couple of years ago, cover to cover. You would be surprised how much I was able to understand and retain. I made copious notes at the time. I am presently re-reading and putting those notes into a meaningful form for myself. But learning is an iterative process. Any questions I ask now are fill-in questions or questions I didn't think to ask at the time. Now that I know better where and how to look, I can do MOST of the research myself, but an occasional hand is greatly appreciated. The advantage of being able to mentally visualize a process is that I find it easier to see logic gaps; to ask myself questions like "hey wait a minute; how did that get from here to there?". > > > I raised the question of 'words' with my local Linux Users Group and > > simply got caught in a long debate amongst them with huge digressions > > that resolved nothing to my satisfaction. > > That's because only hardware nuts and operating system geeks really > care :-) > Thanks again for your time. -- Regards Bill Fedora 11, Gnome 2.26.3 Evo.2.26.3, Emacs 23.1.1 -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
