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- RAM bottleneck
October 22, 2005, 9:47 pm
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Chipset : ATI Radeon RS480
Processor : AMD Athlon 64 3500+ @ 995 MHz
Physical Memory : 512 MB (2 x 256 DDR-SDRAM PC2700 @ 166 MHz)
Video Card : ATI Technologies Inc Mobility Radeon XPRESS 200
Hard Disk : ST9100822A
Network Card : Broadcom Corp BCM4306(??) 802.11g Wireless NIC
Network Card : Realtek Semiconductor RT8139 (A/B/C/810x/813x/C+) Fast
Operating System : Microsoft Windows XP Home Edition 5.01.2600 Service
DirectX : Version 9.0c
I recently got a new laptop (a compaq presario r4125). The system specs
are below. My question: Is the RAM acting as a bottleneck, slowing the
computer down? I read the following review for a similar laptop where
the author had concerns about the RAM, i'm not sure if this would apply
to my laptop also http://www.epinions.com/content_190050045572 . So did
i get screwed on this laptop?
Also if i'm going to be adding another 512 megs of memory, is there a
particular type of RAM i should get?
Re: RAM bottleneck
first, why are you underclocking if you want more speed?
second, I myself have a laptop and the slowest thing with a laptop is
the harddisk. unfortunately there are no really fast ones when it comes
to the comparison with desktop hdds.
adding more ram will help, but install a ramdrive and let windows use it
for paging file. you cant trick windows into using your ram instead of
Re: RAM bottleneck
RAM is the least of your worries on an A64 notebook. The biggest bottleneck
is the HDD. The two fastest right now are the Seagate 7200RPM, and the new
Hitachi 7k100 series. The 7k60 series would be next in line. The new 7k100
series nears IDE desktop 7200RPM performance.
As for RAM, you will see little difference between the PC2700 and PC3200. It
will certainly be nothing you feel, and will only even be effective if you
run some seriously memory intensive tasks for long periods of time. If you
do upgrade the RAM and want to add PC3200, you will need to change both
modules in order to get the 200MHz (400DDR) speeds out of it. SPD will set
the RAM to the speed of the slowest module.
Re: RAM bottleneck
If you want an estimate, without any corroborating evidence, I
use a "1/3rd rule". Take the ratio of the RAM speeds. 400/333 = 1.20,
a 20 percent difference. Your applications will suffer from
0 - 6.6% performance loss, by using the slower memory. The
zero percent case happens when a task is CPU bound. The 6.6% case
(or perhaps a bit higher) will happen with something that accesses
more memory. I think a compression application might tend to be
6 or 7% slower. This estimate doesn't take into account the effects
of using command rate 1T versus 2T timing, or the effects of
CAS2 versus CAS3 memory. This estimate also doesn't tell you what
happens when using synthetic programs, like benchmarks - a bandwidth
benchmark will not follow this rule of thumb at all. This rule of
thumb is intended for real applications.
If you wish to play with the laptop, get a copy of A64tweaker.
This allows some parameters to be adjusted, while sitting in
Windows. I don't believe you can actually change the CAS setting
while the computer is running, and perhaps a copy of CPUZ (cpuid.com)
or Everest Home Edition (lavalys.com) can be used to observe whether
a given setting change is actually working or not. You should use
a benchmark program of some sort, to verify that A64tweaker has
actually changed the behavior of the hardware. (Something with
a slight memory bandwidth dependency would be nice.)
A64Tweaker (latest version I've heard of)
A64Tweaker developer thread
Download links listed here as well, with comments on best version:
Here is a picture of A64tweaker - you will be changing the
memory frequency in the lower right - increase it from
166 to the next highest setting, which might be ~180 or so.
Then, if the computer doesn't lock up, run your test program(s),
and see what the real gains are. Chances are, if you are not
too aggressive with the memory clock setting, you'll avoid
Any time you do experiments like this, make sure your hard drive
is backed up first. You can never be too safe...
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