This thread, captured from the IBM Hardware Forum, 5/94, provides a discussion
of 30- vs 72-pin SIMMS; what's the difference, why are they becoming
prevalent on newer 486 motherboards, and what are the advantages of 72-pin over
30-pin? Includes contact information on one company that can convert 30-pin
to 72-pin. Edited: Steve McCoy, 76702,1156.



#: 447927 S13/486/P5 Systems [H]
27-May-94 09:40:53
Sb: #30 vs 72 pin SIMMs
Fm: Scott Ward 76266,3206
To: All

Was wondering if anyone out there knew why they changed the SIMMs from 30 pin
to 72 pins. I have a 486DX2/66 system with 16 megabytes of 60ns 30 pin SIMMS.
When I built the system I chose 60 ns. 4 meg SIMMs instead of 70 ns. SIMMs,
thinking that I would have a better chance of being able to use 60 ns SIMMs on
a pentium motherboard when I eventually upgraded. But of course they shafted me
by going with a 72 pin SIMM (yes, kick me for trying to anticipate a future
need).

My question centers around whether or not there is any benefit to the 72 pin
variety that would make it worthwhile for me get a motherboard that has 72 pin
SIMMs, or should I get a 30 pin motherboard (if they exist for Pentium's) so
that I can use my SIMMs. I have also heard about some outfit that advertises
in PC week that can make SIMMs out of your DRAM chips and I wondered if there
was an adapter somewhere that allowed you to convert 30 pin SIMMs to 72 pin if
I was unable to find a good pentium motherboard that supported 30 pin SIMMS
(provided of course that there isn't some sort of performance hit incurred by
using 30 pin SIMMs).




#: 448248 S13/486/P5 Systems [H]
28-May-94 07:20:07
Sb: #447927-30 vs 72 pin SIMMs
Fm: 'Fred' Kirby [UK] 70734,126
To: Scott Ward 76266,3206

The advantage to 72 pin SIMMS is that you can add them singly to a 32 bit
system whereas 30 pin SIMMs need to be added in banks of 4. Therefore you have
much more flexibility in the RAM configurations that the system will support
and potentially less wastage.




#: 448281 S13/486/P5 Systems [H]
28-May-94 11:00:36
Sb: #447927-30 vs 72 pin SIMMs
Fm: Richard Gagg 72621,2357
To: Scott Ward 76266,3206

I think there are two reasons for the shift to 72 pin simms 1 - you can add
them 1 at a time in 486 systems instead of 4 at a time with the 30 pin types. 2
- I read somewhere that the 72 pin design circumnavigates the Wang patent on
simms therefore saving a small royalty payment for each simm used. FYI there is
a company out there that converts 30 pin simms to 72 pin types --you send them
your old simms and a small service charge and they convert to 72 pin types.
Their name is Autotime - call (503) 452 - 8577. Hope this helps!



#: 448670 S13/486/P5 Systems [H]
29-May-94 23:56:39
Sb: #448281-30 vs 72 pin SIMMs
Fm: Scott Ward 76266,3206
To: Richard Gagg 72621,2357

That looks like the ticket. I don't think I would be able to sell the 30 pin
SIMMs for what I would have to pay for an equivelant number of 72 pin SIMMs.
Thanks for the tip!




#: 448532 S13/486/P5 Systems [H]
29-May-94 13:24:32
Sb: #447927-#30 vs 72 pin SIMMs
Fm: william taylor 73764,604
To: Scott Ward 76266,3206 (X)

A Pentium motherboard should have at least a 64-bit path to ram if its a decent
board. A 64-bit memory bus would require 8 30 pin simms per bank. With the 72
pin variety it only takes 2 per bank to make 64-bits.

The new Mac's also use a 64-bit memory bus and they require 72-pin simms
installed in identical pairs per bank.



#: 448671 S13/486/P5 Systems [H]
29-May-94 23:56:42
Sb: #448532-30 vs 72 pin SIMMs
Fm: Scott Ward 76266,3206
To: william taylor 73764,604

Hmmm... If it doesn't take too much text I would appreciate knowing why the
physical layout of the SIMMs has an impact on the data path. Also another
fellow in this thread indicated that I could send my 30 pin SIMMs to a place to
have them converted to 72 pin SIMMs. If I do this is there any problem
regarding this 64 bit data path? I am also assuming that a good Pentium
motherboard would want 60ns. memory, which is what I have, although the
motherboard I am waiting for is the 100MHZ Pentium that I haven't seen anywhere
yet.



#: 448778 S13/486/P5 Systems [H]
30-May-94 13:41:38
Sb: #448671-30 vs 72 pin SIMMs
Fm: william taylor 73764,604
To: Scott Ward 76266,3206

Without knowing how the 30-pin simms are converted to 72-pin simms, I cannot
comment, but make sure they are producing "non-composite" simm's with your 30
pin chips if you go that route.

The physical layout of simms on a motherboard should not have any effect
on the data path, but the use of "banks of simm's" does. 30-pin simms are 8-bit
chips; therefore 4 are needed for a 32-bit data path. 72-pin simms are 32-bit
chips. In a 486 systems they can be installed one at a time. In a Pentium
system that means having a 32-bit path to RAM. So look for a board that requires
simms to be installed in like pairs. This means a 64-bit data path.



#: 448674 S13/486/P5 Systems [H]
30-May-94 00:12:30
Sb: #447927-30 vs 72 pin SIMMs
Fm: Laurence D. Allen 70302,2502
To: Scott Ward 76266,3206

The new standard is going to be 72 Pin SIMMS because of the 64 Bit data path
that the Pentium has, in other words you would need 8 of the same SIMMS instead
of just 4. So with 72 you only need 2 of the same sims instead of 8.