DRAM memory for NorthStar Horizon

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