Hej NG
Pga. den senere tids diskussioner og spørgsmål omkring RAM og RAM typer
- billigt contra dyrt RAM, synes jeg denne lille artikel kan være meget
informativt, - selvom den er på engelsk.
mvh. Erik Richard
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Our Feature* - What's with all the memory?
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Once upon a time, the memory that went into a Mac was only for a Mac. So
buying the right memory for your Mac was pretty easy as those companies
selling it knew what they were selling it for. More than ever today,
Apple uses memory types that are made for all platforms. The high cost
of proprietary modules is a thing of the past, but getting the right
module can also be a bit more tricky. Just because its a 128MB SDRam,
doesn't mean it's
the right 128MB SDRam for your computer. OWC makes it easy to buy the
right stuff with our Mac knowledgeable staff and online compatibility
guide, but what about moving memory from machines you or someone else
has? Or a clearance deal, etc? What works in what? We're going to tell
you here!
------SDRam DIMMs and SO-DIMMs are all 3.3V, but they are not all the
same. They can be built with different memory device types and have
different speeds. As a result, what works in one machine, doesn't
necessarily work in another. It's not just how fast a module is, it's
what it's built with too. Following is an machine by machine
explanation. This section will conclude with a terms explanation as
well.
Apple G4 PowerMacs 466MHz to 733MHz, all Models including Dual
Processor: Require PC133 3-2-2 or 2-2-2 168 Pin 3.3v SDRam DIMM built
with 8x8, 16x8, 16x16, or 32x8 Memory devices. Four Memory expansion
slots per machine, 1.5GB MAX Addressable.
Apple G4 PowerMac AGP/Sawtooth Models 350Mhz to 500MHz, all Models
including Dual Processor: Require PC100 3-2-2 or 2-2-2 168 Pin SDRam
DIMM built with 8x8, 16x8, 16x16, or 32x8 Memory Devices. Also 100%
compatible with all PC133 Memory of the same specs, although no
performance gain should be expected. Four SDRam DIMM slots per machine,
1.5GB Max Addressable.
Apple G4 'Yikes' PowerMac 350MHz & 400MHz: Require PC100 3-3-3(3-2-2 or
2-2-2 highly recommended) or faster 168 Pin SDRam DIMM built with 8x8,
16x8, or 32x4* Memory Devices. Also 100% compatible with all PC133
Memory of the same specs, although no performance gain should be
expected. Four SDRam DIMM slots per machine, 1GB total Addressable. *Not
all 32x4 based modules are compatible due to memory device controllers
used on SDRam modules. Use only modules that are listed for your Mac
Model*
Apple G3 Blue & White PowerMac 300MHz to 500MHz Models: Require PC100
3-3-3(3-2-2 or 2-2-2 highly recommended) or faster 168 Pin SDRam DIMM
built with 8x8, 16x8, or 32x4* Memory Devices. Also 100% compatible with
all PC133 Memory of the same specs, although no performance gain should
be expected. Four SDRam DIMM slots per machine, 1GB total Addressable.
*Not all 32x4 based modules are compatible due to memory device
controllers used on SDRam modules. Use only modules that are listed for
your Mac Model*
Apple G3 Beige PowerMac 233Mhz to 300MHz Models: Require PC66 or faster
168 Pin SDRam DIMM built with 8x8, 16x8, or 32x4* Memory Devices. Also
100% compatible with all PC100 and PC133 Memory of the same specs,
although no performance gain should be expected. Three SDRam DIMM Slots
per machine, 768MB total addressable. *Not all 32x4 based modules are
compatible due to memory device controllers used on SDRam modules. Use
only modules that are listed for your Mac Model*
Apple iMac 350MHz to 600MHz, all Models: Require PC100 3-2-2 or 2-2-2
168 Pin SDRam DIMM built with 8x8, 16x8, 16x16, or 32x8 Memory Devices.
Also 100% compatible with all PC133 Memory of the same specs, although
no performance gain should be expected. Two SDRam DIMM Slots, 1GB Max
Addressable.
Apple iMac 233/266/333MHz, Apple PowerBook G3 WallStreet(1998): Uses
PC66 or PC100 144 Pin SDRam SO-DIMM built with 8x8 or 16x8 Memory
devices. Two SO-DIMM Slots: Top slot accepts a 2" full size and low
profile size SO-DIMM, lower slot accepts only low profile size SO-DIMM.
Built to Apple Specs, max upper slot memory module is 256MB an max lower
slot memory module is 128MB for a total max of 384MBs upgradeable to.
Apple PowerBook G3 Lombard(Bronze Keyboard/1999): Uses PC66 or PC100 144
Pin SDRam SO-DIMMs built with 8x8 or 16x8 Memory devices. Two SO-DIMM
slots that will accept low profile or 2" full size SO-DIMMs. Maximum
memory is achieved with two standard size 256MB modules for a total of
512MBs addressable.
Apple PowerBook G3 FireWire(Bronze/2000): Uses PC100 144 Pin SDRam
SO-DIMMs 3-2-2 or 2-2-2 built with 8x8, 16x8, 16x16, or 32x8 memory
devices. Two SO-DIMM slots that will accept low profile or 2" full size
SO-DIMMs. Maximum memory is achieved with two standard size 512MB
modules for a total of 1GB addressable.
Apple PowerBook G4 Titanium: Uses PC100 144 Pin SDRam SO-DIMMs, 3-2-2 or
2-2-2 built with 8x8, 16x8, 16x16, or 32x8 memory devices. Two memory
slots that will accept 1.5" and low profile SO-DIMMs are available with
the system designed to address a maximum of 1GB of memory. In their
infinite wisdom (perhaps comes with their 1 Infinite Loop; Cupertino, CA
address) Apple made the Titanium's memory slots .5" smaller than the
previous PowerBook G3 Models. While the Titanium still uses the same
type of memory as the prior G3 Powerbook model, the 2" full height
module will not fit in it. Because of this, the current maximum memory
available for this model is 512MBs via two 256MB low profile SO-DIMMs.
In the future, we do expect to have a 1.5" 512MB module available so
that the 1GB max can be attained, but for now only the PowerBook G3
FireWire can upped to the 1GB. Thank you Apple.
Apple iBook, all Models: Uses PC66 or PC100 144 Pin SDRam SO-DIMMs
3-2-2 or 2-2-2 built with 8x8, 16x8, 16x16, or 32x8 memory devices. One
SO-DIMM slot that will accept only a low profile SO-DIMM module. These
models come with 32MB or 64MB soldered. 256MB is the largest currently
available low profile SO-DIMM compatible with the iBook allowing for a
max of 288MB or 320MB depending on the stock memory soldered.
----------------------------------------
Terms as they apply to the memory listed above:
PC66, PC100, PC133 refer the the max bus speed a module is designed for.
You can use a PC133 module in a PC66 machine, but you can not use a PC66
module in a computer that needs PC100 or PC133.
Bus Speed refers to the speed of the data path.
Memory Controller is a microchip in the computer that handles how memory
is addressed.
Memory Device Controller is microchip on every SDRam module that sets
the property of the SDRam module for the computer's memory controller to
address.
Memory Devices are what is on the SDRam module itself. Each SDRam DIMM
or SO-DIMM has a quantity of memory device chips along with a controller
and other components. The memory devices are the ones that are typically
the same when you look at an individual module. For example, there are
16 8x8 Memory devices on an 8x8 based 128MB SDRam DIMM, 16 16x8 Memory
devices on a 16x8 based 256MB SDRam DIMM, and there are 16 32x8 memory
devices on a 32x8 based 512MB SDRam DIMM. Different devices have
different densities and thus it takes different amounts of them to make
a given size. JDEC and Apple Spec SDRam SO-DIMMs and SDRam DIMMs should
have no more than 16 memory devices on a single module. Some companies
use modules that employ what is know as 'stacking' where a 256MB (for
example) is built with 32 8x8 devices or a 512MB is built with 32 16x8
Memory devices, this is very bad and such modules are not recommended
for many reasons.
3-3-3, 3-2-2, 2-2-2 are all Cas/Ras speed ratings. They refer to how
fast the device completes refresh cycles. 2-2-2, also know as CL2, is
the fastest refresh cycle rating. There is a significant difference
between 3-3-3 and 3-2-2 memory performance, there is a less measurable
difference in day to day use to be seen between 3-2-2 and 2-2-2. Apple
has always included 3-2-2 or faster modules with their G3 Blue&Whites
and newer systems. Apple profiler will tell you what speed your SDRams
are if you have a G4
AGP/Sawtooth or higher, an iMac 350-600MHz, a PowerBook G3
FireWire(2000), or a PowerBook G4 Titanium.
----------------------------------------
So with that all said you can see you need to be careful when moving
memory between machines. Fortunately, it's not so much that a given
module will hurt your computer, only that it won't work. People ask us
all the time why the $70 256MB stick that is 2-2-2 PC100 works for the
Beige G3, but not the G4 AGP/Sawtooth... The performance specs (PC100,
2-2-2) are up to it, but the device type used on that module is not
compatible with the controller in that newer Apple model.
Before I go on, I want to address one of my favorite memory related
issues... The maximum Ram Apple says will work in a machine. There are
many cases where the maximum memory Apple lists for a given model is no
longer the maximum! For example, when the Beige G3 came out, Apple
listed it with a max of 384MBs. This was because at the time the largest
modules available were 128MBs since only 8x8 memory devices were
shipping to make SDRams with. Apple's memory spec limitation was about
what was available and NOT a limitation of the machine, the OS, etc. It
is only on Apple AGP/Sawtooth G4 350-733MHZ where the 1.5GB limitation
is an actual tech limitation on the machine/OS vs. available memory
technology... With current memory technology, you can put up to 4 512MB
SDRam DIMMs into these Macs... But only 1.5GB will show up, not 2GB.
Why are 5V and 3.3V Mac DIMMs, 72 Pin SIMMs for Pre-G3 Macs so much more
than 3.3V SDRam DIMMs the current models use, why does memory cost vary
to begin with? Memory is the most commodity like product that your
computer uses. Relatively speaking, a 128MB 5V DIMM for $139 is a great
buy... While the 128MB SDRam DIMM for $49 is an absolute STEAL! There
are many manufacturers of memory and when there is weaker demand and
over supply, prices go down as these makers compete to unload their
inventories. Some Current SDRam device prices have actually been BELOW
the cost of making them due to the recent slow down of new computer
purchases and the resulting
scaled back buying of SDRam memory for these system's manufacture. Now,
the 5V Mac DIMMs use 4x4 memory devices that are not in any sort of over
supply situation and thus have a more expectable price for their
purchasing... And comparatively, a 128MB 5V DIMM is still about 50% of
what it was costing just 1 year ago. 72 Pin simms use the same 4x4
memory devices, but have a simpler module design and thus stay in line
just a little cheaper than the 5V DIMMs. To me, if you need it and can
use it, memory is the right price regardless.... And rewind just 5 years
and your had only 32MBs going for about $800! It's tough to complain
about the cost of memory today!
Another question that comes up has to do with older Mac models that use
5V DIMMs. To nip that at the bud, I will be quick and clear.... SDRam
DIMMs do not work in any thing less than an Apple Beige G3 PowerMac. The
5V DIMMs that the older non-G3s use (this includes non-G3s that have
been upgraded to a G3 or G4 processor too.. Your memory slots are still
the same) do not work with the new computers. The good news is that not
only do these parts not work in the machines as noted above, they also
do not fit. While having the same number of pins, the 'breaks' on the
module's connector are in slightly
different positions causing a 'see-saw' effect when you try to insert a
wrong module into your computer. If you have a module that is
'see-sawing' when you try to push it down, you likely have the wrong
module or are trying to put a module in backwards if it's the right one.
PowerMac 4400, 7220/200, and Motorola StarMax/StarMax clones use 3.3V
DIMMs. Are these the same as the 3.3V SDRam DIMMs? NO! Once again, these
are 2 different types of modules and only the right module will fit in
your computer with the wrong one giving that 'see-saw' effect.
4K vs 2K PowerMac DIMMs and SIMMs, whats the difference? The difference
has to do with the block size pattern of the refresh. In practical
terms, 2K is the recommended type for your Mac. Some Mac models will not
even recognize 4K parts. For those Macs that do accept parts that are
recognized by the system as 4K, it is possible to have system
instabilities and especially if you have a G3 or G4 Upgrade. 4K memory
is cheaper, but only buy it if you plan not to upgrade the system with a
G3/G4 processor and also make sure that you never mix 4K modules in the
same bank with a 2K.
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All right, that is a lot to digest. Hopefully there is something for
everyone there and PLEASE, feel free to e-mail your questions to
<larry@owc.net>. Another simple way to see what's right is to use our
online compatibility guide, it will show you what module types work with
specs for the computer you select:
http://eshop.macsales.com/MyOWC/index.cfm
***************************************************************************
--
K.M.L. Denmark by Erik Richard Sørensen, Member of ADC
Edwin Rahrsvej 20.3.03, DK-8220 Brabrand, Denmark
Phone: (+45) 8625 0963, Fax: (+45) 8625 0962
Mobile phone: (+45) 4082 6109, E-mail: <kml.ers@mail1.stofanet.dk>
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