2 Aug
2014
2 Aug
'14
11:38 a.m.
Hello All,
Does anyone have an old National Semiconductor memory data book lying around? I have found
the problem with my second 32k memory board - 3 bad DRAM chips. This board is populated
with MM5298N-3B chips. I can't find an online data sheet that talks about the speed
grade (I'm assuming that's what the 3 is referring to). The manual for the board (
http://www.hartetechnologies.com/manuals/Northstar/NorthStar%2032k%20RAM-32… ) says
that the RAM is 200ns access time. I can find a source for MM5298N-4B chips, but I
don't know if the 4B is still fast enough. I'll replace the entire bank of 9
chips at the same time so that they are matched.
Thanks for any assistance.
Ian
2 Aug
2 Aug
1:50 p.m.
On 2014 Aug 2, at 8:38 AM, Ian McLaughlin wrote:
Does anyone have an old National Semiconductor memory
data book
lying around? I have found the problem with my second 32k memory
board - 3 bad DRAM chips. This board is populated with MM5298N-3B
chips. I can't find an online data sheet that talks about the speed
grade (I'm assuming that's what the 3 is referring to). The manual
for the board ( http://www.hartetechnologies.com/manuals/Northstar/
NorthStar%2032k%20RAM-32-A.pdf ) says that the RAM is 200ns access
time. I can find a source for MM5298N-4B chips, but I don't know if
the 4B is still fast enough. I'll replace the entire bank of 9
chips at the same time so that they are matched.
The datasheet here shows 3 speed grades on page 3:
http://www.alldatasheet.com/datasheet-pdf/pdf/148601/NSC/MM5298.html
-2A -2B: 150ns
-3A -3B: 200nS
-4A -4B: 250nS
Going by the timing relationships on page 18 of the board manual vs.
the datasheet timing specs, it looks like the -4 will be too slow.
(IMO, I wouldn't worry about needing to replace the whole bank.)
Coincidentally, just yesterday I was repairing a Northstar 16K DRAM
board, nearly identical design but with 4K chips. Shorted tantalum,
failed regulator, and 2 bad TI 4027 chips (no spares in my stock
bins, darn it).
3 Aug
3 Aug
8:29 a.m.
There is a datasheet here for the MM5298 familiy:-
http://pdf1.alldatasheet.com/datasheet-pdf/view/148601/NSC/MM5298.html
Looks like these chips are really MM5290 (16K) which are half faulty. From
what I remember the "N" denotes plastic packaging. I suspect you can
substitute the MM5290 which are available here:-
http://www.ebay.com/itm/251002386694
at a reasonable price, in the right speed variant...
Dave
G4UGM
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Ian McLaughlin
Sent: 02 August 2014 16:38
To: General Discussion: On-Topic and Off-Topic Posts
Subject: DRAM memory for NorthStar Horizon
Hello All,
Does anyone have an old National Semiconductor memory data book lying
around? I have found the problem with my second 32k memory board - 3 bad
DRAM chips. This board is populated with MM5298N-3B chips. I can't find an
online data sheet that talks about the speed grade (I'm assuming that's what
the 3 is referring to). The manual for the board (
http://www.hartetechnologies.com/manuals/Northstar/NorthStar%2032k%20RAM-32-
A.pdf ) says that the RAM is 200ns access time. I can find a source for
MM5298N-4B chips, but I don't know if the 4B is still fast enough. I'll
replace the entire bank of 9 chips at the same time so that they are
matched.
Thanks for any assistance.
Ian
10:05 a.m.
There is little value in replacing all the chips. Replace the bad
ones.
The chips you purchase will be NOS. They are almost as likely to
have one or more bad ones as the ones on your board.
As was mentioned, it looks like the chips you have are the those
that were half good.
Also look for chips with the same pinouts from other manufacture.
Most of these 8K and 16K chips were interchangeable, although Motorola
was famous for making something not match other manufactures parts.
Things like a select inverted or RAS vs CAS refresh.
Many RAM test do not test retention of DRAMs. Most are designed to
hold for a minimum of 2 seconds but many can hold for much longer.
You can not tell if your board is doing refresh if you are constantly
reading the chip. It is necessary to stop reading for a period
of time ( with refresh still active ) and then go back and read the
memory locations. Funny failures can sometimes be traced to lack
of there being a refresh cycle. Just reading a location refreshes it so
it can hide the fact that it is not getting a refresh cycle in many RAM
test.
Dwight
11:34 a.m.
Very interesting. The data sheet even admits to the fact that it "employs the same
masks and higly reliable production-proven 2-layer plysilicon NMOS technology as the
MM5290".
This explains the strangeness with the -A and -B variants of the chip, and how the
NorthStar memory board can use either -A or -B by changing a jumper (but you can't mix
both on the same board).
It also appears that the MM5290 is much more common as NOS than the MM5298.
Thanks!
Ian
On Aug 3, 2014, at 5:29 AM, Dave G4UGM <dave.g4ugm at gmail.com> wrote:
There is a datasheet here for the MM5298 familiy:-
http://pdf1.alldatasheet.com/datasheet-pdf/view/148601/NSC/MM5298.html
Looks like these chips are really MM5290 (16K) which are half faulty. From
what I remember the "N" denotes plastic packaging. I suspect you can
substitute the MM5290 which are available here:-
http://www.ebay.com/itm/251002386694
at a reasonable price, in the right speed variant...
Dave
G4UGM
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Ian McLaughlin
Sent: 02 August 2014 16:38
To: General Discussion: On-Topic and Off-Topic Posts
Subject: DRAM memory for NorthStar Horizon
Hello All,
Does anyone have an old National Semiconductor memory data book lying
around? I have found the problem with my second 32k memory board - 3 bad
DRAM chips. This board is populated with MM5298N-3B chips. I can't find an
online data sheet that talks about the speed grade (I'm assuming that's what
the 3 is referring to). The manual for the board (
http://www.hartetechnologies.com/manuals/Northstar/NorthStar%2032k%20RAM-32-
A.pdf ) says that the RAM is 200ns access time. I can find a source for
MM5298N-4B chips, but I don't know if the 4B is still fast enough. I'll
replace the entire bank of 9 chips at the same time so that they are
matched.
Thanks for any assistance.
Ian
---
Filter service subscribers can train this email as spam or not-spam here:
http://my.email-as.net/spamham/cgi-bin/learn.pl?messageid=9EFEF1921B0A11E49…
11:36 a.m.
On Aug 3, 2014, at 8:07 AM, Al Kossow <aek at bitsavers.org> wrote:
On 8/2/14 8:38 AM, Ian McLaughlin wrote:
Thanks! I have grabbed it.
Ian
Hello All,
Does anyone have an old National Semiconductor memory data book lying around?
FWIW
the 1980 memory databook is on bitsavers under national/_dataBooks now
3622
days inactive
3623
days old
6 comments
5 participants
participants (5)
-
aek＠bitsavers.org -
dave.g4ugm＠gmail.com -
dkelvey＠hotmail.com -
hilpert＠cs.ubc.ca -
ian＠platinum.net