Memory limits (was: anyone have a cheap source for pc3200 memory?)
On Sun, Apr 20, 2008 at 4:13 PM, Bruce Labitt <[EMAIL PROTECTED]> wrote: >> Be warned that a lot of older hardware is limited to a 32-bit (4 >> GiB) hardware address bus (even if the CPU has a 36-bit bus). If so, >> the system will not be able to "see" the full 4 GiB of RAM. (The RAM >> gets bumped out of addressable space by other hardware.) You should >> get at least 3 GiB of usable RAM, maybe 3.5 GiB or so. YMMV. > > Scientific linux - above limits do not apply There you're wrong. Linux, running on the proper x86 hardware, can indeed access hardware located above the 4 GiB mark. To do so, it uses something called PAE (Physical Address Extension). PAE is a feature of most x86 processors made in the past several years. It expands the size of the physical address bus -- the actual address pins coming out of the processor -- from 32 to 36 lines. PAE also changes the organization of the page tables inside the processor (to support 36-bit physical addresses), and modified the processor's MMU (Memory Management Unit) to handle all that. However, just because the OS and processor can address more than 4 GiB of hardware, it does not follow that the rest of the system does. The memory controller (located in the "northbridge" chip on the motherboard) has to support it. The motherboard manufacturer has to actually run traces for those extra four lines. The motherboard firmware ("BIOS") has to actually support setting up physical address space above 4 GiB. Your PCI bus controller and cards have to implement DAC (Dual Address Cycle), which is needed to support 64-bit PCI addressing in a 32-bit PCI slot. If you don't have *all* of those things, then your computer will not be able to access hardware (RAM or otherwise) above the 4 GiB physical address mark. If so, the regions needed for I/O, ROMs, etc., will be mapped below 4 GiB. Otherwise, that hardware would not be usable. Those I/O regions will "shadow" the RAM at those physical addresses. The RAM is there, but unreachable. Exactly how much RAM gets eaten up depends on the size of the regions requested by the peripheral hardware. From what I've read, I guess it's typically the size of your video card's onboard RAM, plus the size of the AGP aperture, plus a few tens of MB for other stuff (disk controller, network controller, ROMs, etc.). All this only applies if your hardware limits you in this fashion -- but apparently, quite a lot of hardware does. The IBM-PC platform isn't exactly know for its forward-thinking design. It's even worse in the Microsoft Windows world, where most versions of Windows don't support PAE. (You have to buy the "Enterprise Server" versions to get it for 32-bit, or one of the 64-bit versions of Windows that nobody supports.) I've read stories of people buying twin 512 MB video cards, only to discover to their horror that they lose over 1.5 GiB of RAM to memory mapped I/O. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: anyone have a cheap source for pc3200 memory?
On Sun, Apr 20, 2008 at 4:13 PM, Bruce Labitt <[EMAIL PROTECTED]> wrote: > I need 184 pin pc3200 (400 MHz DDR1) The designation "PC3200" implies "DIMM, SDRAM, 400 MHz, DDR (first-generation)", so those matches should, well, match. :) > ideally low density Well, that's a different matter. I dunno about any designation in common use for memory densities. Is that a limitation of the motherboard chipset or something? >> http://www.google.com/products?q=PC3200+1GB&scoring=p > > Most of the link shows bogus information. Yah, you get that a lot on the Internet. You have to separate the wheat from the chaff. I don't think we're seeing the same hits. The first five hits I get are totally bogus, for example. :) We're prolly getting different Google servers or something. But here's some promising hits culled from the first few pages (leaving out all the eBay matches): http://www.bzboyz.com/ProductDetails.asp?ProdID=3293 http://www.onsale.com/shop/detail.aspx?dpno=7192316 I have no idea about memory density, nor if those vendors are in any way reliable. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: anyone have a cheap source for pc3200 memory?
I am seeing similar issues shopping for 1GB 200-pin CL 2.5 PC2700 DDR for the not-that-old Thinkpad T42. Mobo slots limited to (2) 1GB SODIMMs, no advantage to faster than PC2700/DDR333 but could apparently use PC3200 if I could find it in 200-pin SODIMM (?). -- Bill [EMAIL PROTECTED] [EMAIL PROTECTED] ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: anyone have a cheap source for pc3200 memory?
Ben Scott wrote: > On Sun, Apr 20, 2008 at 11:34 AM, Bruce Labitt <[EMAIL PROTECTED]> wrote: > >> It has PC3200 memory (DDR 1 400 MHz). Anyone know of an >> inexpensive source for some 1MB sticks? >> > > I assume you mean "1GB". Yes. > A Google Product Search finds vendors > selling it on eBay for as cheap as $15 per 1GB stick. I didn't find anything that would actually work on my mobo an intel d865perl. Sure,I think I can find something cheaper than $50/stick, but don't think anywhere near $15. (Especially after shipping!) I need 184 pin pc3200 (400 MHz DDR1) ideally low density. I'm sending an email to the $15/stick vendor (+$10 shipping!) to see if I can use the "high density = cheaper" rather than the low density = $60/stick + $8 shipping. > You're still > paying too much, but at least it's not $50/stick. > > http://www.google.com/products?q=PC3200+1GB&scoring=p > > Most of the link shows bogus information. I.e., stuff shows up but the links don't seem to be good anymore. link #1: this item is no longer available link #2: not pc3200 memory link #3: laptop with 128 MB RAM link #4: laptop with 512 MB RAM - no longer available link #5: no longer available ... etc. grumble, ok, there was a good link ==> ebay pc3200 > Be warned that a lot of older hardware is limited to a 32-bit (4 > GiB) hardware address bus (even if the CPU has a 36-bit bus). If so, > the system will not be able to "see" the full 4 GiB of RAM. (The RAM > gets bumped out of addressable space by other hardware.) You should > get at least 3 GiB of usable RAM, maybe 3.5 GiB or so. YMMV. > Scientific linux - above limits do not apply - only the mobo limit itself. > >> I originally thought it might be cheap. However, from what I have seen, >> it has now passed into the realm of rather expensive relative to the >> performance you get. >> > > Yah, tech pricing tends to follow a bathtub curve. When it first > comes out, it's rare and expensive. As it goes mainstream, it gets > cheap. As it becomes obsolete, prices go back up as it gets hard to > find -- anyone who still wants it must *really* need it. > > -- Ben > ___ > gnhlug-discuss mailing list > gnhlug-discuss@mail.gnhlug.org > http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/ > > ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: anyone have a cheap source for pc3200 memory?
On Sun, Apr 20, 2008 at 11:34 AM, Bruce Labitt <[EMAIL PROTECTED]> wrote: > It has PC3200 memory (DDR 1 400 MHz). Anyone know of an > inexpensive source for some 1MB sticks? I assume you mean "1GB". A Google Product Search finds vendors selling it on eBay for as cheap as $15 per 1GB stick. You're still paying too much, but at least it's not $50/stick. http://www.google.com/products?q=PC3200+1GB&scoring=p Be warned that a lot of older hardware is limited to a 32-bit (4 GiB) hardware address bus (even if the CPU has a 36-bit bus). If so, the system will not be able to "see" the full 4 GiB of RAM. (The RAM gets bumped out of addressable space by other hardware.) You should get at least 3 GiB of usable RAM, maybe 3.5 GiB or so. YMMV. > I originally thought it might be cheap. However, from what I have seen, > it has now passed into the realm of rather expensive relative to the > performance you get. Yah, tech pricing tends to follow a bathtub curve. When it first comes out, it's rare and expensive. As it goes mainstream, it gets cheap. As it becomes obsolete, prices go back up as it gets hard to find -- anyone who still wants it must *really* need it. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
anyone have a cheap source for pc3200 memory?
I want to eke out some more life out of one of my machines. It has PC3200 memory (DDR 1 400 MHz). Anyone know of an inexpensive source for some 1MB sticks? I'd like 4 of them. DDR1 is now considered ancient. I originally thought it might be cheap. However, from what I have seen, it has now passed into the realm of rather expensive relative to the performance you get. Anyone got a lead on this? I find it tough to swallow spending 1/2 the price of a new mobo+memory+cpu for some old memory... Dilemma: 1. spend $240 on memory, have slow computer... 2. spend $480+ on new mobo/cpu/memory ... If I had the $$$ obviously I'd pick #2. Thanks, Bruce ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/