Skip to main content

Computer memory

DRAM (Dynamic random-access memory)

Physical characteristics

Packaging

  • SIP (Single in-line package)
  • DIP (Dual in-line package)
  • ZIP (Zig-Zag in-line package)
  • SIMM (single in-line memory module)
  • DIMM (dual in-line memory module)

Socket type

  • push-type
  • ZIF (Zero Insertion Force)

SIMM

  • Asynchronous DRAM  (DRAM)
  • Page Mode DRAM (PM RAM)
  • Fast Page Mode DRAM (FPM RAM)
  • Extended Data Out DRAM (EDO RAM)
  • Burst EDO DRAM (BEDO RAM)

Number of pins parity ECC FPM EDO Push-type ZIF Max size
30-pin Yes No Yes No Yes No 16 MiB
64-pin (Apple) Yes Yes Yes Yes No Yes 128 MiB
64-pin (GVP) Yes Yes Yes Yes No Yes 128 MiB
72-pin Yes Yes Yes Yes No Yes 128 MiB

Notes:
  • SIMM 30pin
    • first generation were push-type
    • late generations were ZIF
    • always FPM
    • always 5.0V
    • standard sizes: 256 KB, 1 MB, 4 MB, 16 MB
  • SIMM 72-pin
    • always ZIF
    • can be FPM (early), EDO (mostly), BEDO (late and rare)
    • mostly 5.0V. Some 3.3V with higher capacity.
    • standard sizes: 1 MB, 2 MB, 4 MB, 8 MB, 16 MB, 32 MB, 64 MB, 128 MB

DIMM

  • Single Data Rate Synchronous DRAM (SDR SDRAM)
  • Double Data Rate Synchronous DRAM (DDR SDRAM)

Package FPM / EDO
DRAM		 SDR
SDRAM		 DDR
SDRAM		 DDR2
SDRAM		 DDR3
SDRAM		 DDR4
SDRAM		 DDR5
SDRAM
DIMM 168-pin 168-pin 184-pin 240-pin 240-pin 288-pin 288-pin
SO-DIMM n/a 144-pin 200pin 200-pin 204-pin 260-pin ?
MicroDIMM n/a 144-pin 172-pin 214-pin N/A N/A N/A
Voltage 5.0V 5.0V
3.3V		 2.5V 1.8V PC3: 1.5V-1.8V
PC3L: 1.35V
PC3U: 1.25V		 1.2V
1.05V		 1.1V
Speeds measure in ns PC-66
PC-100
PC-133		 PC-1600
PC-2100
PC-2700
PC-3200		 PC2-3200
PC2-4200
PC2-5300
PC2-6400
PC2-8500		 PC3-6400
PC3-8500
PC3-10600
PC3-12800
PC3-14900
PC3-17000
PC3-19200		 PC4-12800
PC4-14900
PC4-17000
PC4-19200
PC4-21300
PC4-25600

Memory is sub-divided in:
  • Buffering: registered (or buffered) / unbuffered
  • Error control: none / parity / ECC
  • Ranking: 1xR8, 1xR16, 2xR8
  • Sides: single / double

Table of Macintosh Ram compatibility

 

68K Classic and Desktop Macintosh....

Mac...

Module format

RAM device compatibility

Install by group of..

Number of slots

Minimum Speed

68000

Plus

30-pin SIMM

N, P - FPM

2

4

150ns

SE

30-pin SIMM

N, P - FPM

2

4

150ns

Classic

30-pin SIMM

N, P - FPM

2

4

150ns

68020

II

30-pin SIMM

N, P - FPM

4

8

120ns

LC

30-pin SIMM

N, P - FPM

2

2

100ns

68030

SE/30

30-pin SIMM

N, P - FPM

4

8

120ns

ClassicII

30-pin SIMM

N, P - FPM

2

2

100ns

Color Classic

30-pin SIMM

N, P - FPM

2

2

100ns

Color ClassicII

30-pin SIMM

N, P - FPM

2

2

100ns

IIx

30-pin SIMM

N, P - FPM

4

8

120ns

IIfx*

64-pin SIMM

N, P - FPM

4

8

80ns

IIcx

30-pin SIMM

N, P - FPM

4

8

120ns

IIci

30-pin SIMM

N, P* - FPM

4

8

80ns

IIsi

30-pin SIMM

N, P - FPM

4

4

100ns

IIvx, IIvi

30-pin SIMM

N, P - FPM

4

4

80ns

LC II

30-pin SIMM

N, P - FPM

2

2

100ns

LC III, LC III+

72-pin SIMM

N, P - FPM

1

1

80ns

LC 520

72-pin SIMM

N, P - FPM

1

1

80ns

Performa 200 see ClassicII

Performa 400, 405, 410, 430 see LC II

Performa 450, 460, 466, 467 see LC III

Performa 600, 600CD see IIvx

Mac TV

72-pin SIMM

N, P - FPM

1

1

80ns

68040, 68LC040

Quadra 605

72-pin SIMM

N, P - FPM

1

1

80ns

Quadra, Centris 610

72-pin SIMM

N, P - FPM

1 (Int)

2

80ns

Quadra 630

72-pin SIMM

N, P - FPM

1

1 or 2*

80ns

Quadra, Centris 650

72-pin SIMM

N, P - FPM

1 (Int)

4

80ns

Quadra, Centris 660AV

72-pin SIMM

N, P - FPM

1

2

70ns

Quadra 800

72-pin SIMM

N, P - FPM

1 (Int)

4

60ns

Quadra 840AV

72-pin SIMM

N, P - FPM

1

4

60ns

Quadra 700

30-pin SIMM

N, P - FPM

4

4

80ns

Quadra 900, 950

30-pin SIMM

N, P - FPM

4

16

80ns

LC 475, LC 550, LC 575

72-pin SIMM

N, P - FPM

1

1

80ns

LC 580

72-pin SIMM

N, P - FPM

1

2

80ns

LC 630, LC 630 DOS*

72-pin SIMM

N, P - FPM

1

1 or 2*

80ns

Performa 475, 476 see LC 475

Performa 550, 560 see LC 550

Performa 575, 576, 577 see LC 575

Performa 63x, 630 DOS, 640 DOS see LC 630

Comments : 

  • "Module format" column shows only what is the format of the RAM slots on the Mac. 68 K Mac only use SIMM modules of RAM. There are two main sorts of SIMM modules :
    • 30-pin SIMM which have 8-bits data path and 
    • 72-pin SIMM which have 32 bit data path. 
    That's why Mac whose data path is 16 bits wide (like Plus, SE) need 30-pin SIMM to be installed by 2, and those whose data path is 32 bits wide needs 30-pin SIMM to be installed by 4 at a time or 72-pin SIMM installed by 1.
  • "RAM devices compatibility" column helps to know with which sort of RAM devices can Mac works. RAM modules are composed of DRAM or SDRAM devices (or chips).  To simplify, all SIMM RAM modules have "DRAM" devices, which can be of two sorts : FPM type (Full Page memory) or EDO. Apple originally installed FPM memory on 68k Mac.
    According to Apple, "EDO (Extended Data Out -- sometimes called hyperpage) memory are DRAM devices that improve access timing by extending its data out timing while allowing the memory controller to address the next column address". It seems that only a few 68k Mac accept EDO Ram, that's why I only precise the compatibility with FPM RAM for all 68k Mac.
    If you buy 2nd hand RAM, you have to know that, in general case :
    • RAM which come from 68k Mac will all be FPM
    • RAM from PowerMac can be FPM or EDO (see my RAM compatibility guide for PowerMacs)
    • RAM from PC with a 386 (or less) processor are all FPM 30-pin SIMM
    • RAM from 486 are FPM or EDO SIMM (30 or 72-pin)
    • RAM from Pentiums are EDO or SDRAM, 72 pin SIMM
    So you'll be able to determine easily which PC RAM you can buy for your Mac (ex: for a SE you need "2 identical 30-pin FPM SIMM, with parity or not" which you can find on a 386).
    In the same "RAM devices compatibility" column, you'll se N and P.
    • N stands for Normal and
    • P stands for with Parity.
    What does it signifies ? Parity RAM modules works with 9 bit words instead of 8, the ninth one is used as control bit. It is simply ignored by all 68k Mac. So you can install RAM with parity on all 68k Mac, which is useful because most old PC used RAM with parity (and PC RAM is cheaper...). Normal modules have a even number of devices, and modules with parity have an odd number of devices...logical, isn't it ?

    FPM ECC memory can be used when FPM is required, if it is unbuffered.

  • "Minimum Speed" column indicates the minimal refresh period of RAM which is needed for the computer to work properly. It decreases with the processor speed, as you can see. The refreshing time is indicated on ram devices with a negative number, which represents the decimals of the time. For example a chip on which I read -12 has a 120ns minimal refreshing time. Of course you can install RAM modules whose refreshing time is far less than what the Mac need (installing 120ns RAM on an SE is better than installing 150 ns). If you have to install 2 or 4 modules at a time (ex: IIsi) they need to be of the same refreshing time. 
  • "Int" means Interleaving. It concerns some Quadra which take benefit of the installation of 2 identical SIMM modules in banks 1,2 or 3,4 (they run 5-10% faster). 
  • Some special cases
    • Mac IIci comes with two sorts of motherboards (See apple memory guide for more information.): 
      • one which needs parity modules to work, and 
      • one which can work with both normal and parity modules.  
    • Mac IIfx uses special 64-pin SIMM, the same as used on Laserwriter IInx. But if you can install modules from a IIfx on the laserwriter, you can't do the opposite because RAM modules installed on Laserwriter have a too long refreshing time. 
    • Some LC 630 have a mainboard with only one SIMM slot, and some come with two slots but with one on which you can only install 1, 4 or 16 Mb modules. 
    • DOS compatibility Cards for Quadra and LC-630 also use 1 72-pin SIMM module, which has to be FPM (I tried an EDO one on my Performa 630 but it didn't worked). Parity modules might be supported.


Source: https://www.jagshouse.com/ram_guide.html

Comments

Post a Comment

Popular posts from this blog

Movie - Bastille Day | The Take (2016)

  My views Plot On the eve of  Bastille Day  in  Paris , American drifter and  pickpocket  Michael Mason steals a woman's handbag, not knowing that it contains  explosives . After taking the cash from the bag, he discards it, caught unwittingly on  CCTV  as he does so. The bag then detonates and kills four people. Upon being captured by  CIA  agent Sean Briar, who is being reprimanded for irresponsible conduct on the job, Mason protests that he is not a  terrorist  and tells Briar that the bag contained a cellphone owned by a woman named Zoé. The bomb was set up by a group of  corrupt policemen , all of them members in the  French special police RAPID unit  led by Rafi Bertrand, who intend to pull a robbery at the  Bank of France . Zoé was told to plant the bomb at the office of the  French Nationalist Party  (as part of a diversion for the heist), but after seeing the night cleaning crew arri...
Post a Comment
Read more

Movie - Se7en (1995)

  My views Plot In an unnamed city overcome with violent crime and corruption, disillusioned police Detective Lieutenant William Somerset is one week from retirement. He is partnered with David Mills, a young, short-tempered, idealistic detective who recently relocated to the city with his wife, Tracy. On Monday, Somerset and Mills investigate an obese man who was forced to eat until his stomach burst, killing him. The detectives find the word " gluttony " written on a wall. Somerset, considering the case too extreme for his last investigation, asks to be reassigned, but his request is denied. The following day, another victim, who had been forced to cut one pound (0.45 kg) of flesh from his body, is found; the crime scene is marked " greed ." Clues at the scene lead Somerset and Mills to the  sloth  victim, a drug-dealing  pederast  whom they find emaciated and restrained to a bed. Photographs reveal the victim was restrained for precisely one year. Somers...
Post a Comment
Read more

Movie - The Gray Man (2022)

  My views Plot In 2003, senior  CIA  official Donald Fitzroy visits a prisoner named Courtland Gentry in Florida. Eight years earlier, Courtland was a minor convicted of killing his abusive father to protect his brother. Fitzroy offers him his freedom in exchange for working as an assassin in the CIA's  Sierra  program, an elite black ops unit, which will allow him to exist in the gray. In 2021, Courtland, now known as  Sierra Six , is working with fellow CIA agent Dani Miranda to assassinate a target named Dining Car suspected of selling off  national security  secrets in  Bangkok  during the national  Songkran  festival. Unable to do so stealthily without harming civilians, he attacks Dining Car directly, mortally wounding him. Before dying, he reveals he was also in the Sierra program as Sierra Four. He hands Six an encrypted drive detailing the corruption of CIA official Denny Carmichael, the lead agent on the assassinatio...
Post a Comment
Read more