# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1362868581 -3600
# Node ID b0163096b9041f67b4c1fa8bd4b3cd03f64bb20d
# Parent  36e18a580b52dbb0b93154b3fa2ff9e8debc1c90
Added information on the RAM ICs and modern replacement parts.

diff -r 36e18a580b52 -r b0163096b904 ULA.txt
--- a/ULA.txt	Thu Feb 21 20:04:40 2013 +0100
+++ b/ULA.txt	Sat Mar 09 23:36:21 2013 +0100
@@ -126,6 +126,25 @@
 with approximately 15 blank lines above and below the picture. Thus, the start
 of the picture could be chosen as 38 lines after the start of vsync.
 
+RAM Integrated Circuits
+-----------------------
+
+The documentation for the Electron mentions 4164-15 RAM chips for IC4-7, and
+the Samsung-produced KM4164 series is apparently equivalent to the Texas
+Instruments 4164 chips presumably used in the Electron.
+
+The TM4164EC4 series combines 4 64K x 1b units into a single package and
+presumably could be used to replace the Electron's separate ICs, but it has 22
+pins providing 3 additional inputs and 3 additional outputs over the 16 pins
+of the existing modules, presumably allowing concurrent access to the packaged
+memory units.
+
+As far as currently available replacements are concerned, the NTE4164 is a
+potential candidate. According to the Vetco Electronics entry, it is
+supposedly a replacement for the TMS4164-15 amongst others. Meanwhile, the
+NTE21256 appears to be a 16-pin replacement for all four ICs that maintains
+the single data input and output pins.
+
 See: Acorn Electron Advanced User Guide
 See: http://mdfs.net/Docs/Comp/Electron/Techinfo.htm
 See: http://en.wikipedia.org/wiki/PAL
@@ -138,6 +157,14 @@
      http://www.pembers.freeserve.co.uk/World-TV-Standards/Line-Standards.html
 See: TM4164EC4 65,536 by 4-Bit Dynamic RAM Module
      http://www.datasheetarchive.com/dl/Datasheets-112/DSAP0051030.pdf
+See: KM4164B 64K x 1 Bit Dynamic RAM with Page Mode
+     http://images.ihscontent.net/vipimages/VipMasterIC/IC/SAMS/SAMSD020/SAMSD020-45.pdf
+See: NTE4164 - IC-NMOS 64K DRAM 150NS
+     http://www.vetco.net/catalog/product_info.php?products_id=3680
+See: NTE21256 - IC-256K DRAM 150NS
+     http://www.vetco.net/catalog/product_info.php?products_id=2799
+See: NTE21256 262,144-Bit Dynamic Random Access Memory (DRAM)
+     http://www.nteinc.com/specs/21000to21999/pdf/nte21256.pdf
 See: Acorn Electron Service Manual
      http://acorn.chriswhy.co.uk/docs/Acorn/Manuals/Acorn_ElectronSM.pdf