IBM System/23 Datamaster: Difference between revisions
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=== RAM Memory ===
RAM in the Datamaster is completely contained in one to two boards complementary to the motherboard and are attached through a card-edge connector of 36 pins each. This facilitates the removal and placement of memory cards into the system and grants the possibility of fast repair and extension of the computer. There are two memory slots, and at the same time official memory boards were produced in two sizes: 32KB and 64KB respectively. This led to five possible official configurations.
{| class="wikitable" style="float:right;" |
|+ Official RAM configurations
|-
! Feature board !! Option board !! Total
|-
| 32KB || None || 32KB
|-
| 32KB || 32KB || 64KB
|-
| 64KB || None || 64KB
|-
| 64KB || 32KB || 96KB
|-
| 64KB || 64KB || 128KB
|}
Still, it is known that the official maximum of 128KB is just the maximum for the earlier models of 5322, as later revisions could address up to 256KB by configuring some jumpers in the motherboard. This is possible as the bank control register is implemented with a 74LS670, which is 4 bits wide, giving 16 pages of 16KB each. Additionally, there is a non-banked page which is used among other things as the display memory. For this reason the actual theorical maximum memory for a System/23 is 272KB. Still, it has been hinted that some clones of the system exist and that those expand the width of the page register to eight bits, giving the theorical maximum to 4112KB to them.
The memory boards contain one or two TMS4132 arrays of 9 memories each. Having nine units per bank allows them to have a data byte width of data plus a ninth bit for parity. Both because of the rareness of the format of the TMS4132 and the replacement of the official reference led for years to believe that IBM soldered the memories in piggyback to cope with failure rates when in reality it was a feat of Texas instruments to sell them directly soldered after manufacture of both dies. This kind of memory contains a 16KB bank per package and both packages have a slight difference of the pinout to not have conflict with /CAS and /RAS.
Memory is subject to many diagnostics tests, some of which are considered critical and could prevent the system from successfully IPL, giving the impression of a completely dead computer whereas only the memory could be failing. It has also been tested that the computer won't boot if no memory board is present at the "feature" socket.
=== Diagnostics port ===
[[File:20240409 143826.jpg|thumb|left|alt=System/23 diagnostics port|System/23 diagnostics port]]
The System/23
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