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

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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