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Chuckster_in_Jax
February 22nd, 2012, 08:55 AM
I have an IBM 9595-OQT 66 mhz Pentium. It only has 16MB of RAM and I would like to bump that up using 32MB SIMMs. The IBM memory module is listed as a 72pin SIMM Parity ECC 70ns . There are some sites that reference the module as being 5v (8x39), others that don't mention that.

I can easily find (8x36) modules on eBay, but not (8x39). Sites that have the (8x39) want outrageous sums of money for it.

Does anyone know what the (8x39) means and what would actually work in this machine?

joekster
February 22nd, 2012, 12:15 PM
I have heard of x40 72pin simms, maybe only x39 is used. In regular x36 ecc can detect and fix a single bit error. In x40(x39???) ecc can detect and fix two bits in error. Not sure if that machine really requires x39, or if x36 would be fine...

IBMMuseum
February 22nd, 2012, 06:34 PM
I have an IBM 9595-OQT 66 mhz Pentium. It only has 16MB of RAM and I would like to bump that up using 32MB SIMMs. The IBM memory module is listed as a 72pin SIMM Parity ECC 70ns . There are some sites that reference the module as being 5v (8x39), others that don't mention that.

I can easily find (8x36) modules on eBay, but not (8x39). Sites that have the (8x39) want outrageous sums of money for it.

Does anyone know what the (8x39) means and what would actually work in this machine?

http://ibmmuseum.com/ohlandl/config/memory_error_correct.html#ECC

Uncommon - and heavily fought over when it had the highest availability on eBay (probably around ten years ago)...

Having 256Mb on a 486 (the 9585 K/N model uses a slightly different type) or early Pentium is a good feeling...

But it was hard enough at the time that I'm not letting it go...

Chuckster_in_Jax
February 22nd, 2012, 06:46 PM
http://ibmmuseum.com/ohlandl/config/memory_error_correct.html#ECC


A 9595 XP 486 machine can use either parity or non parity. Is the 95 Server(my 9595-OQT) limited to only the ECC modules with parity?

Unknown_K
February 22nd, 2012, 08:20 PM
I didn't know the RAM was that rare, I have 160MB I believe in my P66 9595.

IBMMuseum
February 22nd, 2012, 08:24 PM
A 9595 XP 486 machine can use either parity or non parity. Is the 95 Server(my 9595-OQT) limited to only the ECC modules with parity?

http://ibmmuseum.com/ohlandl/complexes/Type4-Q.html#Memory

An 8595 is a Type 1 or Type 2 complex (on the appropriate planar), a 9595 is a Type 3 ('M' DX-50) or Type 4 complex...

Chuckster_in_Jax
February 23rd, 2012, 11:03 AM
Did some Google searches on IBM's 32MB SIMM P/N 92G7210.
(This condenses the info in IBMMuseum's first post)

Lenovo's website lists it as 32MB EOS (8MX39) 70ns (72-Pin):

http://support.lenovo.com/en_US/product-and-parts/detail.page?&LegacyDocID=MIGR-46140

Another site describes What is Parity, ECC and EOS? mentions that


EOS has no added protection over normal ECC.
Hewlett Packard and IBM are the only sources for EOS limiting availability and adding to the cost.
EOS will cost much more, take longer to get or replace, and statistically less reliable than normal ECC


The difference between (8x39) and (8x36) is from:

32-bit data path requires 7 bits for ECC or 4 bits for parity


http://www.advantagememory.com/Home_Page/support_link/faq/what_is_parity.htm