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diff --git a/zk/Magnetic_drum_memory.md b/zk/Magnetic_drum_memory.md
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+---
+title: Magnetic_drum_memory
+tags: [computer-history, memory]
+created: Tuesday, September 24, 2024
+---
+
+# Magnetic drum memory
+
+Along with the [Williams_Tube](Williams_Tube_memory.md), another early approach
+to RAM used in 1950s-1960s era of computing.
+
+![Magnetic drum](../img/magnetic-drum-memory.jpg)
+
+A magnetic drum was a metal cylinder coated with a magnetic material. Data was
+stored by magnetising small regions on the drum's surface. The drum would rotate
+at high speeds and read/write heads were positioned along the length of the drum
+to access data.
+
+Seen as a improvement on Williams Tubes and
+[delay line memory](Delay_line_memory.md) but superseded by magnetic core memory
+later. It's concept lived on in harddisk drives which became the dominant form
+of secondary storage.
+
+It had a larger capacity than the technologies that preceded it and it was also
+non-volatile - the data would remain intact when the power was turned off.
+
+It was used in the [IBM 650](The_History_of_Computing_Swade.md) (1953) and
+Ferranti Mark I (1951)
diff --git a/zk/The_History_of_Computing_Swade.md b/zk/The_History_of_Computing_Swade.md
index e2ebd30..1843a39 100644
--- a/zk/The_History_of_Computing_Swade.md
+++ b/zk/The_History_of_Computing_Swade.md
@@ -529,27 +529,37 @@ computer industry with the UNIVAC.
 
 IBM's first electronic computer. It directly competed with the UNIVAC for
 government contracts. It followed the prevailing approach of vaccuum tubes for
-logic and had a variety of storage methods: Williams tubes, magnetic tape, and
-magentic drums.
+logic and had a variety of storage methods: Williams tubes,
+[magnetic tape](Magnetic_tape.md) , and magentic drums.
 
 701s were used at Los Alamos and avionics companies. Some were also used to
 manage payroll in business contexts.
 
-### IBM 702 ("Tape Processing Machine")
+### IBM 702 ("Tape Processing Machine") (1953)
 
 ![Advertisement for the IBM 702](../img/ibm-add.jpeg)
 
-Focused primarily on business applications. Used magnetic tape for...
+Focused primarily on business applications and targetted at businesses rather
+than government contracts. Less powerful than the 701.
 
 ### IBM 650
 
-Low-cost general purpose machine using magnetic drum memory. It was
-mass-produced unlike the others which were built for specific customers. It
-proved the breakout star in IBMs initial line up and sometimes called "IBM's
-Model T".
+![IBM 650](../img/ibm-650.jpg)
+
+Low-cost general purpose machine using magnetic drum memory. Marketed as slower
+but more affordable than the 700 range. It was mass-produced unlike the others
+which were built for specific customers. It was in fact the first mass-produced
+computer in the world. It proved the breakout star in IBMs initial line up and
+sometimes called "IBM's Model T".
+
+![IBM_650 console panel](../img/ibm-650-console-panel.jpg)
 
 IBM offerred 650s to univesities at a 60% discount on the condition that the
 universities would establish courses in computing. This was shrewd as it meant
 that a whole generation of engineers and computer scientists learned on 650s and
 would prefer them in their research. It also created a pool of skilled users
 that would go on to work at IBM.
+
+Donald Knuth dedicated _The Art of Computer Programming_ to the 650.
+
+It used magnetic drum memory along with vacuum-tubes.
diff --git a/zk/Williams_Tube_RAM.md b/zk/Williams_Tube_memory.md
similarity index 93%
rename from zk/Williams_Tube_RAM.md
rename to zk/Williams_Tube_memory.md
index 7aa38f9..a49bdfb 100644
--- a/zk/Williams_Tube_RAM.md
+++ b/zk/Williams_Tube_memory.md
@@ -1,10 +1,10 @@
 ---
-title: Williams_Tube_RAM
+title: Williams_Tube_memory
 tags: [computer-history, memory]
 created: Tuesday, September 17, 2024
 ---
 
-# Williams Tube RAM
+# Williams Tube memory
 
 - One of the early attempts to create RAM in computers based on the EDVAC
   stored-program architecture.