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- Vista Workshop: More RAM, More Speed
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- DDR3-1333 Speed and Latency Shootout
- PC Memory: Just the Facts
- The New Arms Race: DDR3-1800 RAM
- Hardcore DDR2 RAM by Corsair, G.Skill, OCZ and Patriot
- Overclocking 9 Value-Priced DDR2-800 Kits
- Corsair's PC10000 Super-Ober-Uber-RAM Sets Sails
- Corsair's XMS2 Dominator: The World's Fastest DDR2?
- Live Memory Test: Overclock 'Em Till They Crash
RAM Usage
Source: Tom's Hardware – Keywords: ram, scaling, notebook
Syndication:
RAM Usage
RAM is not only used by the operating system to store all system and application data that is currently being used—think of the operating system kernel, extensions and applications—but also as a cache for application data. Once you terminate an application, the memory content will be conserved until other memory requests require the main memory content to be overwritten. But as long as the content is physically still there, a terminated Adobe Photoshop, for example, will restart much faster than when you launched it for the first time.
Windows Vista also has a feature called SuperFetch, which automatically preloads applications into available main memory once there is sufficient free main memory. Should memory capacity be required by your applications, Vista will flush the SuperFetched data, but in every other case it will provide much quicker application launch times.
Powerful applications require increasing amounts of main memory to work at full performance. Photoshop editing a 24x36” photo at 600 dpi will eat approximately 2 GB of RAM. 3D games typically load high-resolution textures into the main memory as well.
RAM Capacity vs. Power Consumption
While memory modules with more chips or higher memory densities certainly require more power when compared within one memory technology, doubling the memory capacity per DIMM does not even remotely double the RAM power requirements. This means that exchanging two 512 MB SO-DIMMs for two 1 GB DIMMs will have a minor impact on system power consumption, and hardly any effect on notebook battery runtime.
There are several reasons why sufficient RAM will not only introduce performance benefits, but also save some energy on notebooks:
- Windows doesn’t have to work extensively with a swap file on your hard drive, which would cause higher power consumption due to intensive hard drive activity. Windows can even stop a hard drive when idle.
- Having more RAM will allow Windows and applications to perform as quickly as possible, hence reducing processing times by avoiding involvement of the hard drive. DRAM is typically faster and more energy-efficient than a hard drive.
- Mechanisms such as caching or SuperFetch can do their job more effectively. Completing a task efficiently allows the notebook to go back into a more energy-efficient state as quickly as possible.
- Previous page Upgrading the Latitude D630
- Next page Varying RAM Capacities
I'll stick with XP and my 2GB of Corsair until a version of Linux that doesn't require you to wander in to the console every five minutes comes along.
...one nice thing though is that the reviews consider reasonably priced equipment. I don't care about 8800 Ultras, 9800GX2s, or thousand dollar CPUs. I've got more important priorities then trying to impress people who aren't getting any work done.
The fastest SSD I've seen has read/write speeds of approximately 110MBps/80MBps and an access latency of about 0.1ms.
If significantly faster SSDs are currently for sale, please forgive me for not keeping up with storage tech the way I used to. (BTW, FusionIO is neither an SSD nor affordable outside of datacenters)
To simplify things we'll just use the faster of the two.
110MBps = 880 Mbps
This is roughly the effective throughput of single channel DDR-400 on an AthlonXP chipset. (Memtest86(+))
It is a little more than half the effective throughput of the single channel DDR-400 controller on the socket 754 Athlon 64 systems.
It is less than a quarter of the effective throughput of the dual channel DDR2-800 controller on an Athlon64 X2.
I don't have readily available numbers on an Intel DDR3 system, but you can see where this is going.
(I could have put in Intel memory controller results and/or AthlonXP dual channel results, but these numbers fit better to get the general feel of things)
These results aren't bad actually.
SSDs may not have reached even the last generation of memory technology, but at least in throughput, they match RAM technology that was widely used to run Windows XP.
Side note: If you use theoretical bandwidth, then SSDs can't reach DDR-400 (3200Mbps) until the interface gets upgraded to 4GHz (~400MBps).
If the numbers seem funny to you, it's because I'm taking into account the 10/8 encoding scheme that SATA uses.
The real kicker is the access time.
0.1ms seems very fast in HDD terms, but on a 2GHz processor, this is about 200000 cycles of latency.
Compare that to:
150-165 cycles for the AthlonXPs
125-140 cycles for P4s
~60 cycles for Athlon64s
RAM is made to be accessed very often in relatively short bursts.
Until SSDs can get the latency down, they have no hope of replacing RAM.
If mass storage were as quick as RAM, you wouldn't dedicate part of it to be used as RAM.
Rather, you would manipulate the files directly from the mass storage device.
This would eliminate RAM all together, reducing overhead and potentially power consumption.
Unfortunately, no current mass storage device has the potential to do that.
I'm still waiting for MRAM to make its appearance.
It used to hold promise, but after waiting so long I lost interest and stopped keeping up with it.
Perhaps it can do what flash can not.
Feeding the OS endless amounts of ram is not a long term solution to an underlying performance issue. I can run Ubuntu linux with all the fancy compiz-fusion eye candy with just 512mb and it's smooth. Vista doesn't run smooth even with 1gb; it's a real dog. I understand why everyone is avoiding it like the plague, except of course those poor unfortunates who bought into the Direct X 10 marketing fallacy, and others who bought a new machine with it preinstalled (microsoft tax).