# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1596238410 -7200
# Node ID 940fdf55c25170d5858e741815a1114eeeedacb6
# Parent  0fa3ae6ff36b1abfaf930e630b50f86157f8705e
Added notes about memory pricing and other machines using the 4164.

diff -r 0fa3ae6ff36b -r 940fdf55c251 Electron.txt
--- a/Electron.txt	Tue Apr 28 22:51:23 2020 +0200
+++ b/Electron.txt	Sat Aug 01 01:33:30 2020 +0200
@@ -88,6 +88,9 @@
 peripheral would maintain its own framebuffer by registering writes on the bus
 to the display memory region.
 
+Memory Performance and Economic Considerations
+----------------------------------------------
+
 Of course, the economic considerations related to the choice of RAM products
 could be revisited, reviewing the assumption that the products chosen would
 have significantly lowered the total production cost. This might indicate that
@@ -111,7 +114,36 @@
 less than half of the originally anticipated memory costs. (Naturally, eight
 32Kbit memory chips, which might also have exhibited similar price reductions,
 would potentially have offered the delivered 32K for an even smaller fraction
-of the anticipated costs.)
+of the anticipated costs, although it is not clear that such 32Kbit devices
+were widely available.)
+
+Employing eight 1-bit devices would also have permitted the use of slower
+parts. The TM4164EC4-15 used in the Electron has a row access time of 150ns
+and a column access time of 90ns, with two column accesses required per byte.
+It is conceivable that a 200ns part, potentially with a slower column access
+time, would have been satisfactory when only a single access is required per
+byte. This is pertinent when considering the evolution of the pricing of the
+4164, as seen in contemporary publications such as Personal Computer World
+where advertisements suggest a declining retail price for the 200ns part:
+
+June 1982       £4.65 (Happy Memories)
+August 1982     £4.50 (Opus Supplies)
+October 1982    £4.20 (Happy Memories, Opus Supplies)
+February 1983   £3.55 (Happy Memories)
+
+The 150ns is reported as costing £4.00 in a Technomatic advertisement in
+February 1983. It may be the case that UK retail advertising does not
+illustrate the sudden decline from the initial pricing of the 4164 to its
+eventual pricing with sufficient availability. However, a general indication
+of pricing evolution can be glimpsed in a Midwich Computer Company Limited
+advertisement in November 1981 which appears to feature the Fujitsu MB 8264,
+rated at 200ns and described as a 64Kbit part, at a unit price of £11.00 in
+volume.
+
+Other contemporary microcomputers offered 64K RAM using 4164 parts, such as
+the Sony SMC-70 and, more pertinently, the Atari 800XL. The latter of these
+appears to have employed 150ns-rated parts - eight as indicated above - and
+may have had a broadly similar production cost to the Electron.
 
 Improving Display Capabilities
 ------------------------------