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Topic: CAS Latency

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	SpeedGuide.net Broadband Community - SDRAM Cas Latency
		CAS Latency is measured in CPU clock cycles with the lower number being the fastest and the highest being the slowest.
		The CAS Latency value can usually be changed to the following settings: "1", "2", "2.5", or "3" depending on your available BIOS options.
		If using different CAS latency memory in your configuration such as one chip being CAS 2 the other CAS 3 do not set the memory to the lower CAS 2 setting as this can cause stability errors.
	forums.speedguide.net /printthread.php?t=96351 (354 words)

	CAS Latency
		Recently, a whole raft of resellers have been publishing comments that the CAS Latency on their Brand X modules are a huge improvement over that of Brand Y modules sold elsewhere.
		The RAS to CAS latency will be 0 (zero) cycles and the output buffers will contain the right data after the CAS latency.
		This second example, with a CAS Latency of "4", would be invalid in a 133 Mhz.
	www.dewassoc.com /performance/memory/cas_latency.htm (1200 words)

	[H]ard\|Forum - ram latency
		Certainly, one of the most important timings is that of the CAS Latency and is also the one most people understand.
		In other words, CAS Latency is the delay between the CAS signal and the availability of valid data on the data pins (DQ).
		It is also dependant on CAS latency, so on the same platform, the optimal tRas value for cas 1.5 and cas 2 could be different.
	www.hardforum.com /printthread.php?t=854193 (565 words)

	CAS - Column Access Strobe, RAS - Row Access Strobe latency (Site not responding. Last check: 2007-10-17)
		Latency is the time it takes for the memory devices, after getting a command and address to produce its first data word.
		CAS latency is the clock cycles between the issuance of the read command and when the data comes out.
		In lay terms, CAS Latency times the system clock cycle length must be greater than or equal to the column access time (tCAC).
	www.bugclub.org /eric/memory/caslatency.html (378 words)

	Writings - CAS Latency
		The maximum latency is approximately 120 ns with a stride length of 1024 bytes.
		However, with a CAS latency of 3 clock cycles the degenerate memory latency increases to almost 128 ns -- a 7% increase.
		These values are well within statistical uncertainty limits, therefore leading to the conclusion that while CAS latency has a measurable impact on kernel microbenchmarks, for most general-purpose multiprocessing application loads (whose performance is affected to a large degree by I/O performance) it is irrelevant.
	myphotos.dyndns.org /caslatency.asp (1022 words)

	TechIMO Forums - Cas latency question (Site not responding. Last check: 2007-10-17)
		Is cas latency 2.5 better than 3 looking for memory and saw the differant numbers and was wondering what the differance was.
		CAS stands for Column Access Strobe (conversely, RAS stands for Row Access Strobe) and CAS Latency is the amount of delay that you have to wait between the CAS signal and the data being pushed from the RAM pins.
		CAS2 latency essentially means we have a 2 cycle delay, and CAS3 has a 3 cycle delay: hence the lower the CAS, the lower the latency, and the better your performance.
	www.techimo.com /forum/printthread.php?t=118405 (462 words)

	CGTalk - Ram Level!!!
		The first number is CAS Latency, second is CAS-to-RAS delay and third is RAS precharge time.
		CAS Latency - CAS latency is a setting which determines the column access time for the RAM in your system.
		The lower the latency, the faster and more frequently the computer is able to access the RAM for different pieces of information.
	forums.cgsociety.org /printthread.php?t=27751 (832 words)

	CAS Latency - Wikipedia, the free encyclopedia
		CAS is an acronym for column address strobe, or sometimes column address select, both referring to the column of the physical memory location in an array of capacitors (a grid comprised of columns and rows) used in dynamic random access memory modules.
		Latency refers to the amount of time, or lag, that is experienced in traversing a system.
		When selecting a RAM card the lower the CAS latency rating the better your system will perform.
	en.wikipedia.org /wiki/CAS_Latency (229 words)

	Memory upgrades from Crucial.com - Memory term definitions (Site not responding. Last check: 2007-10-17)
		CL stands for CAS (column address strobe) latency, which is the number of clock cycles it takes before data starts to flow after a command is received.
		Low CAS latency at a given frequency is faster than high CAS latency at that same frequency.
		If you don't know the CAS latency of the memory you currently have installed, don't worry; any of the modules listed in the Memory Advisor tool are guaranteed to work in your system.
	www.crucial.com /crucial/pvtcontent/memorytype.asp?model=Presario+5304%2E&memtype=cas (227 words)

	Ace's Hardware (Site not responding. Last check: 2007-10-17)
		The first 2 means that the CAS latency is equal to "2", the second number indicates the RAS to CAS latency and the third the Precharge latency.
		The third column explains the latencies that occur in the situation that is described in the first column.
		Therefore, contrary to some popular belief, latency and bandwidth are very closely related, especially in a typical pc system which accesses the main memory mostly to fill a cacheline.
	www.aceshardware.com /Spades/read.php?article_id=5000173 (917 words)

	DDR2: a Soon-to-be DDR Replacement. Theoretical Basis and First Low-level Test Results
		Additive latency also known as CAS latency is another modification introduced into the DDR2 standard.
		Typical latency values for DDR2 devices can be found in the 12-20ns interval basing on which the CAS latency value is selected.
		The use of higher latency values is inexpedient in terms of memory subsystem performance, while lower ones shouldn't be used as they prevent the memory device from stable work.
	www.ixbt-labs.com /articles2/ddr2-rmma/ddr2-rmma.html (3557 words)

	BIOS CAS Latency Voltage Shadowing Memory Cache (Site not responding. Last check: 2007-10-17)
		Specifically, CAS latency only refers to the waiting time for the first column access in a burst transfer of data that transfers multiple memory elements and spans multiple columns in a row of memory.
		This means that CAS 2 and CAS 3 memory have similar burst transfer timing characteristics beyond the first memory presented at the memory chip output pins.
		In fact, adjusting CAS timing is a relatively gentle way to coax three or so more percent performance from your system, and holds less potential for damage because you're not really increasing the clock speed of the whole memory subsystem.
	www.gen-x-pc.com /bios4.htm (1615 words)

	The Definitive Review Of The 256MB Crucial PC2100 DDR SDRAM DIMM
		CAS latency now appears to have very minimal effect on performance.
		In addition, while you can reduce the CAS latency from 2.5 to 2, the two other important latencies of tRCD (minimum RAS to CAS delay) and tRP (minimum row precharge time) have increased to 3, which is one clock cycle higher than that of normal SDRAM.
		That increases the importance of the tRCD and tRP latencies and minimizes the effect of lowering the CAS latency from 2.5 to 2.
	www.adriansrojakpot.com /Reviews/Crucial_PC2100/PC2100_09.htm (313 words)

	Hardware CAS-latency (Site not responding. Last check: 2007-10-17)
		De tijd vanaf het begin tot aan het eind (terugkeer van data) noemen we de CAS latency.
		Nu is het niet zo dat CAS 2 33 procent sneller is dan CAS 3, ondanks dat dit theoretisch wel zou zijn.
		Er spelen meer factoren (en tevens andere latencies) mee, waardoor CAS 2 een paar procent sneller is. Niettemin is het dus wel raadzaam om hier op te letten bij de aanschaf van geheugen!
	hardware.computerpech.nl /cas-latency.html (331 words)

	In Computer Memory what is CAS Latency? (Site not responding. Last check: 2007-10-17)
		Latency refers to the time that you are waiting to get what you need.
		Then, the column address is put on the address pins, and the CAS signal is activated, to access the correct COLUMN of the memory matrix.
		In that case, CAS is only activated ONCE, at the beginning of the burst.
	www.womencentral.net /cas-latency.html (544 words)

	Ars Technica: RAM Guide: Part II: Asynchronous and Synchronous DRAM - Page 5 - (7/2000) (Site not responding. Last check: 2007-10-17)
		The CAS latency is the delay, in clock cycles, between the registration of a READ command and the availability of the first piece of output data.
		To see the relationship between CAS latency and bus speed in a real world setting, let's take a look at the CAS latency chart for the SDRAM we've been studying.
		You'll notice that the higher the bus speed goes the higher the CAS latency has to be.
	www.arstechnica.com /paedia/r/ram_guide/ram_guide.part2-5.html (701 words)

	FiringSquad RAM Guide (Site not responding. Last check: 2007-10-17)
		What CAS 2 and 3 actually denote is the time it takes to transfer data internally from the memory bank to the output buffer running at 100 MHz.
		Okay, this reads CAS latency must be equal or greater than the column access time divided by the system clock cycle.
		In this example, then, both modules are CAS 3 at 125 MHz, which means that spending extra money on a CAS 2 module is not worth it, because there is no performance benefit.
	www.firingsquad.com /guides/ram/page12.asp (722 words)

	LostCircuits, Memory Reviews
		On a page hit, the latency that decides how early the critical word is output is the CAS latency.
		In clear text, this means that the read command can be issued early, that is exactly one CAS latency before the end of the burst without trashing the data in the output buffers.
		To reiterate, in an SDRAM situation, the additional latency of a CAS-3 part cannot be hidden, even in page hit situations, in a DDR scenario, there is no real impact of CAS-2 vs. CAS 2.5 while staying in page.
	www.lostcircuits.com /memory/ddr2/2.shtml (926 words)

	SDRAM FAQ (Site not responding. Last check: 2007-10-17)
		CAS latency refers to the number of clock cycles between the application of the SDRAM's column address and the appearance of the data at the output of the module.
		A CAS latency 2 module requires 2 clocks between the application of the column address and the data.
		Systems using CAS latency 2 (CL2) SDRAM's are typically a few percent faster than systems using CAS latency 3 SDRAM's.
	www.corsairmicro.com /main/tsdramfaq.html (719 words)

	TIHE - Tonga Institute of Higher Education (Site not responding. Last check: 2007-10-17)
		That is basic speed test of the memory module.
		However there is another important factor in high performance memory and that is CAS latency.
		CAS meaning Column Access Strobe, the basics of CAS latency are that CAS latency is the amount of clock cycles it takes for the response from the memory from a query.
	www.tihe.org /encyclopedia/Ram.php (932 words)

	X-bit labs Community :: View topic - RAM CAS Latency Question
		So the absolute latency for a given module should be the same regardless of clock speed, although relative to the clock it will appear to vary.
		The lower the cas timings then the more closer (or more bunched up) the memory transactions are going to be (so long as RAS and all the other stuff are sorted as well).
		The general reason why you see a higher performance boost of slower ram when you make the CAS timings more agressive that is shown by the relationship of the amount of data processed by the ram per second in relation to the amount of data processed by the CPU per second.
	www.xbitlabs.com /forum/viewtopic.php?t=3270 (5853 words)

	PC3200 в двухканальной упряжке: экстремальный подход
		Одна из наиболее важных скоростных характеристик памяти DDR - CAS Latency.
		CAS - это сокращение от Column Address Strobe, что в литературном переводе выглядит как "строб доступа к адресу столбца".
		Latency, она же "латентность", она же "задержка",- одно из ключевых явлений микроэлектроники вообще.
	www.izcity.com /data/hard/article368.htm (1850 words)

	Frequently asked questions (FAQs) at Crucial.com (Site not responding. Last check: 2007-10-17)
		CAS latency (also referred to as latency) is the amount of time it takes for your memory to respond to a command.
		Unless you are a computer enthusiast looking to push every last bit of performance out of your system, CAS latency needn't be a deciding factor when purchasing memory modules.
		The performance difference between CAS latency ratings is virtually undetectable.
	www.crucial.com /kb/answer.asp?qid=3657 (137 words)

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		Please note that some memory modules may not be able to handle the lower latency and may lose data.
		Therefore, while it is recommended that you reduce the SDRAM CAS Latency Time to 2 or 2.5 clock cycles for better memory performance, you should increase it if your system becomes unstable.
		Interestingly, increasing the CAS latency time will often allow the memory module to run at a higher clock speed.
	www.rojakpot.com /showFreeBOG.aspx?Lang=0&bogno=190 (178 words)

	Sdram cas latency (Site not responding. Last check: 2007-10-17)
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	sdram-cas-latency.omim.nl (156 words)

	Does RAM Latency Matter?
		CAS is the amount of time, in cycles, between receiving the column access command and acting upon it.
		The first latency measurement that comes into play is tRAS, as the memory waits to activate the row where the data resides.
		Then CAS is the time it takes to select the proper column of memory and retrieve data stored there.
	www.extremetech.com /article2/0,1558,1637826,00.asp (1038 words)

	Ars Technica: RAM Guide: Part II: Asynchronous and Synchronous DRAM - Page 6 - (7/2000) (Site not responding. Last check: 2007-10-17)
		In particular, tCAC (column access time), which is the minimum amount of time you have to wait between the moment you latch in the column address and the moment the data shows up at the output pins, is a direct factor in determining what CAS latency you need for what bus speed.
		Obviously, there would be more clock pulses in between the time that the column address was latched onto the bus and the time that the first data showed up on the bus.
		Since tCAC is the limiting factor in the latency, you have to be able to multiply the clock period by the CAS latency and have the result be greater than or equal to tCAC.
	www.arstechnica.com /paedia/r/ram_guide/ram_guide.part2-6.html (697 words)

	PortaTech.com - What is CAS latency 2 vs. 3? (Site not responding. Last check: 2007-10-17)
		Cas Latency is a rating of how fast the memory module can complete the second section of the read/write cycle.
		CAS 2 parts can complete the second section of the cycle in 2/10th of the complete cycle, a CAS 3 part needs to have 3/10th of the cycle allocated to this section.
		Some systems (usually higher speed Athlon or Brand Name systems) cannot run with the slower CAS 3 memory.
	www.portatech.com /faq.asp?ID=7 (91 words)

	Tech Support Forum - CAS Latency for DDR memory
		But all I have seen are mostly CAS latency 2.5.
		I guess the ideal situation is to get 2.0 CAS PC2700 memory, overclock the FSB to 166Mhz, and unlock CPU multiplier and REDUCE it to match it's original core speed.
		latency to work in 2.0 CAS mode (meanig 2.5 was ok) on the ASUS A7V333 mother.
	www.techsupportforum.com /archive/index.php/t-1324.html (1390 words)

	DriverHeaven.net - CAS latency in RaBit?
		I noticed settings for CAS latency and such and was just thinking about messing with those.
		I wasnt gunna do super ram timings but I wanted to see about cas latency since on my system RAM it makes huge differences depening on CAS latency.
		Sorry for the stupid, but I got the wrong card when I bought my X800 pro VIVO and just got the RMA yesterday and since it was the right card and RaBit came out with X800 support so I took it as a sign and flashed it to 16 pipes 500/540.
	www.driverheaven.net /printthread.php?t=56661 (775 words)

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