On Fri 22 Jun 2007 11:51:07 NZST +1200, Roger Searle wrote: > It seems to be a popular suggestion in the windows world to NOT get 4GB > of ram for a windows box due to the limitations in the ability of > windows to fully address all 4GB given a 32bit operating system. Is the > same true of linux generally speaking,
These 4GB are mostly a limitation of mathematics (2^32 = 4G) and a little bit of the hardware. 32 bit give you an address space of 4GB, some of it is used for memory-mapped I/O by PCI cards and this that and the other. If you get 3.8 usable GB you're doing well, less than 3.6 is bad. Luckily the days of the Intel Brain Fart(TM) are gone - those twats were telling everyone for years that needing 2x16bit to address 16MByte of memory thus wasting 8 bits of pointer space and creating a hideous addressing-ambigouity is a good thing. Obviously what you should be doing is use 64bit hardware and software. You ought to have a pretty good reason not to. Ok except for doze, with which you never need a reason, switching down the IQ and following the lemmings never leads to job loss. > and that there is little point in > getting 4GB? There is good reason to get either 2GB or 4GB. You won't have more than 4 memory slots unless you buy a golden mobo, which may have 8 or 12 slots and take up to 4GB in each slot (don't bother looking for a 32bit one of those). They work like clockwork with Linux I hear. On a 32bit mobo each slot will take a max of 1GB, and there is some mechanism which can read 64bit from 2 memory modules in the same time as it takes to read 32bit from one, giving you a speed increase. This only works if you fill up with modules symmetrically, and is the reason each two slots are colour-coded. > I like the idea of using a raid 1 configuration that is offered by > motherboards now to provide data redundancy, Do not even consider it! Make sure you keep a huge distance between those useless mobo raid chips and any raid software you might have. Those chips are exclusively for those who think that using a proprietory software raid driver for proprietory software raid chips gives them any advantage whatsoever over built-in solid proven Linux kernel software raid with generic IDE/SATA hard disk ports. I.e. stupid Microsofties for whom those chips are the closest they'll get to raid, and gullible Linux users who didn't see through the FUD of Promise & Co. If you want raid performance buy a hardware raid card, I think 3ware are the only hardware ones. No Promise don't have any, they only sell you expensive non-performant software raid disguised on a special-made card. Nuff said. > Last question (whoops, more than a couple of points): if you have a 400W > power supply for example, is this always drawing power from the mains at > 400W regardless of what is being drawn internally from the motherboard > and components attached to it? Power is like water: if it goes in, it has to go out too. Conversion losses in the PSU are converted to heat: out = in - losses. You can neglect the mechanical part used by the fan(s). The max specified on the power supply is the maximum you can draw out of each rail added together. What you aren't drawing on one rail you can't make up on another, each rail has a strict maximum - make sure you take this into account when calculating current requirements! The power going in is what you're drawing out, minus the losses which are ballpark 20% of what goes in (i.e. the conversion has an 80% efficiency). Btw when you do the maths, you find that you only need a smaller supply than what the hype suggests. Catch: cheap supplies don't work properly at their specified full load (yes they're lieing). Those 600W / 1000W or shock 1400W supplies for gaming PCs are targeted at those with a combination of too much testosterone, too much money, and not enough brain. Check online reviews for what the good models are, but assess whether the review you're reading is more than drivvel and the people know what they're talking about. silentpcreview.com are good. Volker -- Volker Kuhlmann is list0570 with the domain in header http://volker.dnsalias.net/ Please do not CC list postings to me.
