2e about ram expos

7/25/2019 2e About Ram Expos

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About RAM

What is RAM?

RAM is our working memory storage. All the data, which the PC uses and workswith during operation, are stored here.

To examine RAM, we need to look at the following:

RAM types !PM, "#$, "CC, and %# RAM&

RAM modules %'MM and #'MM& in different (ersions RAM and the system )us

!irst, let us look )ack in time. *ot too many years ago, +ill ates said, that with -M+ RAM, we had a memory capacity, which would ne(er )e fully utilied.

Historical review

+ack in the /0s, PCs were e1uipped with RAM in 1uantities of 23 4+, 562 4+,6-5 4+ and finally - M+.Around -770, ad(anced operating systems, like 8indows , appeared on themarket, That started the RAM race.


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The first 8indows operated PCs could address 5 M+ RAM, )ut 3 M+ soon)ecame the standard.

The race has continued through the 70s, as RAM prices ha(e droppeddramatically.

Today. it would )e foolish to consider less than 95 M+ RAM in a PC. Many ha(emuch more. -5/ M+ is in no way too much for a power user with 8indows76;7/, it is important with plenty of RAM.

8indows 7/ is a little )etter at handling memory, )ut still a lot af RAM is a goodthing.

RAM types

The traditional RAM type is #RAM dynamic RAM&.

The other type is %RAM static RAM&.

%RAM continues to remem)er its content, while #RAM must )e refreshed e(eryfew milli seconds.

#RAM consists of micro capacitors, while %RAM consists of off;on switches.


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Therefore, %RAM can respond much faster than #RAM.

%RAM can )e made with a rise timeas short as 3 ns. 't is used in different(ersions in


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+y switching from !PM to "#$, one could expect a performance impro(ement of5 to 6 percent.

EDO RAMwas usually sold in 20 ns (ersions. A 60 ns (ersion was a(aila)le at higher cost."#$ has now )een replaced )y the e(en faster %#RAM.

E"" RAMis a special error correcting RAM type. 't is especially used in ser(ers.

#DRAM (synchronous DRAM!!The replacement for #RAM, !PM, and "#$ RAM types. %#RAM lockssynchronies& the memory access to the CP? clock. This way we get fasterdata transfer. 8hile one portion of data is tranported to the CP? another can )e)eing prepared for transfer.%#RAM comes only in 23 )it modules long -2/ pin #'MMs&. %#RAM has a

access time of only 2@-5 ns. The performance impro(ement o(er "#$ RAM wasa mere 6 percent running at 22 M. At -00 and -99 M it pro(es )etter.

DDR RAMis clock dou)led (ersion of %#RAM, which is replacing %#RAM during 500-@5005.


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RAM$%# (RDRAM!is a more futuristic RAM type. 'ntel and others had great expectations from this

type, )ut it flopped in 5000@500-.

& or ' bits per byte?*ormally you figure / )its to one )yte. !or many years, a ninth )it has )eenadded asparity)it in the RAM )locks to (erify correct transmission.

That way you ha(e to transmit 7 )its, to store / )its in the old 90 pin RAM chips.

And it takes 92 )its to store 95 )its in the larger =5 pin chips, which increases thecost of the RAM chip )y a)out -5B.

'f your mother)oard re1uires 92 )it modules, you must respect that. !ortunately,most system )oards accepts 95 )it modules, so this creates no pro)lems.

RAM an otherboar>ou cannot freely install your desired RAM type. RAM is controlled )y the chipset on the mother)oard, so you must install a type, which matches yourmother)oard. !urthermore, RAM chips come in different sies, which mustmatch the system )oard.


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$n modern system )oards, RAM is installed on %'MM or #'MM modules. +efore,small indi(idual #RAMs were used. There was usually room for 92 small chips

on the system )oard. That made it cum)ersome to install new RAM.

Then, someone figured out to install RAM chips on cards, which are easilyinstalled. !irst came the %'PP modules. They had multiple pins, which fit in themother)oard. %ince then came the %'MM modules.

They are mounted on a card, which has an edge connector. They fit in sockets

on the mother)oard, and anyone can install them.


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RAM speesRAM speed is measured in ns nano seconds&. The fewer ns, the faster is the

RAM. >ears ago, RAM came in -50, -00 and /0 ns. Today, we are talking a)out20 ns and faster.

't )ecomes complicated to descri)e the relationship )etween RAM speed andthe a)ility of the system )us to utilie fast RAM. ' will gloss o(er that. +ut here isa ta)le which illustrates RAM speed, relati(e to clock speed:

Clockspeed

Time per clock tick

50 M 60 ns

56 M 30 ns

99 M 90 ns

60 M 50 ns

22 M -6 ns

-00 M -0 ns

-99 M 2 ns


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Pea) $anwithere you see the maximal peak )andwidth of the three well known RAM types.

The figures illustrates the a)solutely maximal transfer from RAM to the


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95 )it processors 9/2# and 3/2& need 3 of the small / )it %'MMs in a )ank,since their )anks are 95 )it wide. %o, on a typical -st generation 3/2

mother)oard, you could install 3 - M+, 3 5 M+, or 3 3 M+ in each )ank. 'fyou only had one )ank with room for 3 modules&, it was expensi(e to increasethe RAM, )ecause you had to discard the old modules.

,- bit oules8ith the ad(ent of the 3/2 processor, demand increased for more RAM. Thenthe larger 95 )it modules came into use. A 3/2 mother)oard could still ha(e 3

%'MM sockets, )ut when the modules were 95 )it wide, they could )e installedone at a time. This was 1uite ingenious.

>ou could add different types of modules and still use the old ones. Also, sincethe 3/2 mother)oard ran at only 99 M on the system )us, the RAM module1uality was not so critical. >ou could mix 20 ns and =0 ns modules of different)rands without pro)lems.

ere you see a couple of %'MM modules. $n top is a 23 )it module -2/ pins @donDt try to count them&. *ext is a 95 )it module with a =5 pin connector. +elow isan / )it module with a 90 pin connector:


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./ bit #DRAM0

95 )it #RAM and -2 )it #RAM:


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*um)er of chips per module%ome %'MMs ha(e more chips on the module than others.


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*$T": ne(er use different speed RAM modules on the Pentium mother)oard. Allmodules mst ha(e the same speed. ere you see a few configurations on an

old Pentium mother)oard with four %'MM sockets:

+ank - +ank 5 Total RAM

-2 M+ G -2 M+ @ 95 M+

-2 M+ G -2 M+ 95 M+ G 95 M+ 72 M+

95 M+ G 95 M+ 95 M) G 95 M+ -5/ M+

Certain mother)oards like T>A*& ha(e 2 or / %'MM sockets. That pro(idesmore RAM expansion flexi)ility.


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D*MMs

The most used modern RAM type, SDRAM is made in 64 bit wide modules

called DIMMs (Dual Inline Memory Module)They ha(e a -2/ pin edge connector. ere you see one module:


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%ince the #'MM modules are 23 )its wide, you can install one module at a time.

They are a(aila)le in /, -2, 95, 23, -5/, 562 M+, and 6-5M+ with 2, /, -0, and-5 ns speed. There are usually 5 @3 #'MM sockets on a mother)oard.

The ad(antage of %#RAM is increased speed. That allows you to increasesystem )us speed. 8ith 20 ns "#$@RAM, you can run at a maximum of =6 Mon the system )us, while %#RAM speed can increase to -99 M and a)o(e.

Also the %#RAM work synchronous with the system )us for a )etterperformance.

Most chip sets are made for %#RAM. %ome mother)oards had )oth %'MM and#'MM sockets. The idea was that you could reuse old "#$ RAM in the %'MMsockets, or choose to install %#RAM in the #'MM sockets.


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They were not designed to mix RAM types although it works at some )oards.

A)o(e: a 23 M+ #'MM@module holding 95 chips each of -2 M)it 95 -2 M)it ;/ )it F 23 M+&.

't is )etter to use #'MMs made of the new 23 M)it chips. A 23 M+ module is this

way made of only / chips / 23 M)it ; / )it F 23 M+&.


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Fast RAM'ntel ha(e managed to speed up the processors power )y factor 500 times the

last ten years. That is a lot, )ut it is a pro)lem that RAM memory technology onlyhas impro(ed )y factor 50 in the same period.Today we hope and dream of new fast RAM types, that will help us to get the fullpotential from our powerful PCs.

P"122 RAMThe first attempt to impro(ing RAM speed was the PC-00 standard. 8ith chip

sets like +the system )us speed has come up to -00 M. ence 'ntel hasmade a new standard called PC-00. $nly / ns %#@RAM modules that areconstructed according to these standards are guaranteed to work at -00 M. 'nsome articles this RAM is descri)ed at -56 %#@RAM.

#PDThe new #'MM@modules include a "PR$M@chip holding information a)out themodule. This little /@pin chip works as a %P# Serial Presence Detect& @ a unitstoring information a)out the RAM type. The idea is that +'$% can read thisinformation and this way tune the system )us and the timings for a perfect CP?@RAM performance.

>ou can find a program, that tests the contents of the %P# at this cDt homepage.'t works with the 'ntel chip sets holding a /59=- south )ridge like + and .Another program is called #'MMH'#.
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P"1,,

3he P"1,,RAM running at -99 M is the latest (ersion of %#RAM. %pecifications aremade )y I'A, Micron, *"C, %amsung, %'%, Acer


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!or a period of -5 months in -777@5000, 'ntel experienced se(eral disastrous

incidents from their attempt to implement Ram)us in chip sets andmother)oards. #uring this period they were forced )y taiwanese mother)oardmanufactures& to adapt the PC-99 standard.

The chip set i/-6was the result of this re(ision of strategies.

'ntelDs pro)lem is that they ha(e sold their soul to Ram)us 'nc. According to

their agreement, until 5009 'ntel can only implement other RAM types thanR#RAM if the )andwidth is less than - +;sec. This agreement does not includeser(er chipsets, from what we understand.

Rabus RDRAM8hile the CP?s has )ecome around 500 times faster in ten years, the RAMperformance has only gone up 50 times. %o we need new RAM types. +utwhichL

Many (endors decided to go for ##R RAM as descri)ed in . 8here ##R RAM isa de(elopment of the existing %#RAM technology, 'ntel choose R#RAM, whichrepresents a much more re(olutionary change in RAM design.
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*ntel an RDRAM without succes

'ntel is comitted to the Ram)us RAM, which also is called R#RAM Ram)us#irect RAM&, n#RAM, or R'MM Ram)us 'nline Memory Modules&.R#RAM is an ad(anced technology patented )y a company, who sells thetechnology to other chip manufactures for a 5B in license. 'n -77= 'ntel signed acontract that apparently commits them to support R#RAM only in all new chipsetup to 5005.

$riginally AM# also expected to support the Ram)us RAM for its Athlonprocessor. +ut ha(ing seen all 'ntelDs pro)lems with the technology, AM# is notso keen on the Ram)us anymore. owe(er, R#RAM is already used in %onyPlay%tation 5 and in *intendo23 machines. 'n the %ony Play%tation 5 you find 95M+ of R#RAM deli(ering a )andwidth of 9.5 +;sec.

#uring -777 and 5000, Ram)us was not (ery successful. 'n fact, 'ntel hassuffered a serious set@)ack due to their commitment to the Ram)us design. Thechip set i/50 Camino )ecame a little disaster.

'ntel failed to produce a relia)le way to interface %#RAM to the /50 chipset. TheMT Memory Translator u) @ which translated R#RAM )us to %#RAMmodules& had some timing or noise issues that caused unrelia)le operation. 'ntelreplaced CC/50 )oards with IC/50 )oards with -5/M+ R#RAM included& asthe CC/50 use the MT and %#RAM while the IC/50 used R#RAM.


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+ut, on the paper, Ram)us sounds great:

*ntelli+ent Rabus esi+nR#RAM is de(eloped from the traditional #RAM, )ut the architecture iscompletely new. 't has )een streamed and optimied to yield new performance.The RAM+?%@design gi(es a more intelligent access to the RAM, meaning thatunits can prefetch data and this way free the CP? some work. The idea is thatdata is read in small packets at a (ery high clock speed.The R'MM modules are only -2 )it wide compared to the traditional 23 )it%#RAM #'MMs, )ut they work at a much higher clock fre1uency:

The Ram)us modules work on 5.6 (olts, which internally is reduced down to 0.6(olt when possi)le. This helps to reduce heat and radio signals.


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The R'MMs hold controlling chips that turns off the power to sections not in use.They can also reduce the memory speed if thermal sensors report of

o(erheating.

"R*MMsAll RAM slots ha(e to )e full this is new, with RAM+?% we ha(e to fill in )lankmodules in slots which are not in use. The )lank modules are called CR'MMswith a DCD for continity&.The R'MM modules hold -/3 pins.

The R#RAM chips ha(e to )e placed (ery close to the CP? to reduce radionoise. This indicates, that R'MM technology is rather sensiti(e 'ntel seems toha(e made that disco(ery as well.


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Hi+h cloc) ratesAs mentioned, the modules are only -2 )it wide, )ut they work at 200, =00 and

/00 M. Actually a PC/00 R'MM runs on a 300 M clock using )oth risingand falling edges, )eing clockdou)led Eust as ##R RAM.More confusing the PC200 R'MM actually runs on a 522;695 M clock, and thePC=00 works at 922;=-5 M.

PC/00 /00;300 M

PC=00 =-5;922 M

PC200 695;522 M

This gi(es the )andwidth of up to -.2 + per second @ compared to the 600@/00M+;sec of PC-00 %#RAM @ of a single Ram)us channel. >ou may find a chartcomparing the )andwiths of different RAM types in the next page.

Multichannel eory esi+n>ou may )undle four channels to a 23 )it wide RAM )us gi(ing 2.3 +;sec:


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This is not possi)le using the existing RAM+?%@)ased chip sets like i/50.Theyonly operate with one RAM+?% channel on)oard. The high@end chip set i/30operates with dual R#RAM channels, as the up@coming i/60 will.

R*MM in the 5uture6 says *nteligaert (ersions of Ram)us RAM will pro)a)ly follow, so the technology haspotential for much higher )andwidths.'n -777 it seemed that 'ntel was ha(ing )ig pro)lems with the Ram)ustechnology in the ill@faited i/50 chip setthe so@called Caminogate tragedy&.ence they were forced to support PC-99 RAM as seen in the i/-6 chipset.

Poor per5orance so 5ar
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?nfortunately it was soon o)(ious that the i/-6 chip set with its PC-99 RAM wasperforming slightly )etter than the i/50 chip set with its still (ery expensi(e

R#RAM. >ou ha(e to use dual Ram)us channels as in upcomming 'ntel chip seti/60 Tehema& to )enefit from a higher )andwidth. +ut this dou)ling is alsopossi)le from using ##R RAM.A test )etween a i/30@)ased dual Ram)us PC and a Micron ##R@)ased PCga(e the same result all )enchmarks were )etter on the ##R system.%o far Ram)us RAM is of no )ig interest. 't is too expensi(e, and there is nothingto gain from it. owe(er the Ram)us technology stil is 1uite promising, )ut theprices has to come down, and it )etter )e soon. ##R RAM is closing in.'ntel claims that ##R is to slow for the new Pentium 3 processor. 't would re1uiredual channel ##R RAM to get the re1uired )andwidth. And dual channel ##RRAM meens a -5/ )it wide )us, which is no good solution. The north )ridge andthe mother)oard would )e loaded with hundreds of signal lines.'n 500- R#RAM is )eing used with great success on the +/60 Pentium 3)oard and R#RAM prices are tum)ling steadily.

RDRAM -72Ram)us plans to speed up the )andwith a factor two using a Nuad Ram)us%ignaling


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##R stands here for Do!le Data Rate. 't is a technology that transmits data on)oth sides of a tact signal.This way the performance has )een dou)led a -99 M %#RAM chip can (eryeasy )ecome altered to a 522 M ##R chip:

't should )e pretty easy for the market to change for ##R RAM. The moduleslook like and operate 1uite similar to existing %#RAMs. 8e Eust need newchipsets to start the migration.

owe(er, the modules hold -2 pins more than %#RAM do, so they do not fit intothe same sockets.

P"-122The Taiwanese company I'A, which produces chip sets and CP?s and who arefighting 'ntel, is fully supporting the ##R RAM strategy. %oon we shall see 522M moduls )eing o(erclocked-99 M %#RAM modules&.The 522 M


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modules reaches a 5.- +;sec )andwidth. ence they are to )e sold as PC5-00RAM.

$ther terms used are:

##R500 500 M&

##R522 522 M&

##R999 999 M&

I'A expects ##R to )e used in all segments of the pc market. 'ntel, who is)ehind the Ram)us technology, only expects to use ##R in large ser(ers, whereyou find se(eral iga)ytes of RAM installed, and where RAM price really

matters.

8o *ntel here'ntel is dedicated to the Ram)us technology. 'n the summer 5000 it was re(ealedthat 'ntel has comitted itself to the RAM+?% technology so they cannotimplement ##RK This goes for all future desktop PCs until 5009, according totheir agreement with Ram)us 'nc. $nly the 23 )it ser(er 'tanium processor and it

succesors !oster and Mc4inley are using ##R RAM.8e hope that 'ntel will change their strategy. 8e expect ##R@%#RAM to )echeaper than Ram)us RAM for 1uite some time yet it should gi(e the sameperformance. Ram)us represents a sophisticated technology, )ut with prices 6times higher it is not a low@end product. 'ntel produces great chipsets for desktopPCs like i/-6", and it would )e sad if they a)andoned this market. 8e want 'nteland PC5-00K
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Reports in the summer 5000 told that 'ntel has licensed I'A to de(elop ##R@ena)led chip sets for Pentium 3.

Evolutionary chan+es o5 esi+n8here R#RAM re1uires completely new production plants, ##R represents ane(olutionary progress. The chip manufactures may re@use their %#RAM fa)s forthe production without many pro)lems.ence it seems 1uite natural and in tune with the pre(ious changes in RAMtechnology that we use the ##R standard for a couple of years. +efore Ram)usor something e(en )etter& enters the market.

"oparin+ banwith+elow you see the theoretical )andwidts of different RAM types. owe(er,%#RAM does not perform as good as the figures show. This is due to latenciesthe CP? and other units cannot read the data at these speeds they ha(e to waitsome clock circles in )etween each reading )efore the data transfers start. Thesame goes for ##R RAM.

RAM type Theoretical max. )andwidth

%#RAM -00 M -00 M 23 )itF /00 M+;sec

%#RAM -99 M -99 M 23 )itF -023 M+;sec


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##RAM 500 M PC-200& 5 -00 M 23 )itF -200 M+;sec

##RAM 522 M PC5-00& 5 -99 M 23 )itF 5-5/ M+;sec

##RAM 922 M PC5200& 5 -22 M 23 )itF 5262 M+;sec

R#RAM 200 M 200 M -2 )itF -500 M+;sec

R#RAM =00 M =00 M -2 )itF -300 M+;sec

R#RAM /00 M /00 M -2 )itF -200 M+;sec

DDR9**A new (ersion of ##R RAM is scheduled for 5009. ?sing another techni1ue, itshould )e possi)le to dou)le the performanceK

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