Difference between revisions of "MB20 core memory"

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The '''MB20''' was a [[core memory|core]] [[main memory]] system for the later [[PDP-10]]s, principally the mid-period [[KL10]]. An MB20 contained up to four memory controllers, each with up to four 32KW storage modules, for a maximum of 512KW; [[parity]] is provided to protect the memory contents. The [[access time]] is 1.04 µseconds, and the [[cycle time]] is 1.92 µseconds (both for the first [[word]] in a 4-word block, using four-way [[interleaving]]).
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The '''MB20''' was a [[core memory|core]] [[main memory]] system for the later [[PDP-10]]s, principally the mid-period [[KL10]]. An MB20 contained up to four memory controllers<sup>*</sup>, each with up to four 32KW storage modules, for a maximum of 512KW; [[parity]] is provided to protect the memory contents. The [[access time]] is 1.04 µseconds, and the [[cycle time]] is 1.92 µseconds (both for the first [[word]] in a 4-word block, using four-way [[interleaving]]).
  
It connected to the so-called internal memory bus, the S-Bus, which performs memory transfers in blocks of 4 words, so that 4 words can be read in any cycle. The KL10 contains a pair of S-Busses; controllers 0 and 1 are connected to S-Bus 0, and controllers 2 and 3 to S-Bus 1.
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It connected to the KL10's so-called internal memory bus, the S-Bus; controllers 0 and 1 are connected to S-Bus 0, and controllers 2 and 3 to S-Bus 1. For interleaving, each controller is configured as to which addresses (out of the 4 in an S-Bus block) it will respond to; both 2-way and 4-way interleaving require controllers to be set to 'odd' or 'even'. In 4-way interleaving, in addition to two controllers being actuated at the same time, each controller can start two modules reading at the same time.
  
[[Category: PDP-10 memories]]
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<nowiki>*</nowiki> - <i>DEC documentation conflicts on this; the 'MB20 Internal Memory Unit Description', EK-MB020-UD-001, December 1976, says optionally four (pg. 1-1) - and has generally been followed for this writeup; the 'DECsystem-10 DECSYSTEM-20 Processor Reference Manual', AA-H391A-TK, July 1980, says two (pg. G-18).</i>
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==See also==
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* [[MA20 core memory]]
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==External links==
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* [http://www.bitsavers.org/pdf/dec/pdp10/KL10/EK-MB020-UD-001_Dec76.pdf MB20 Internal Memory Unit Description] (EK-MB020-UD-001)
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* [http://www.bitsavers.org/pdf/dec/pdp10/memory/MP00179_MB20_Schematic_Aug76.pdf MB20 Field Maintenance Print Set] (MP00179)
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[[Category: PDP-10 Memories]]

Revision as of 13:47, 22 April 2022

The MB20 was a core main memory system for the later PDP-10s, principally the mid-period KL10. An MB20 contained up to four memory controllers*, each with up to four 32KW storage modules, for a maximum of 512KW; parity is provided to protect the memory contents. The access time is 1.04 µseconds, and the cycle time is 1.92 µseconds (both for the first word in a 4-word block, using four-way interleaving).

It connected to the KL10's so-called internal memory bus, the S-Bus; controllers 0 and 1 are connected to S-Bus 0, and controllers 2 and 3 to S-Bus 1. For interleaving, each controller is configured as to which addresses (out of the 4 in an S-Bus block) it will respond to; both 2-way and 4-way interleaving require controllers to be set to 'odd' or 'even'. In 4-way interleaving, in addition to two controllers being actuated at the same time, each controller can start two modules reading at the same time.

* - DEC documentation conflicts on this; the 'MB20 Internal Memory Unit Description', EK-MB020-UD-001, December 1976, says optionally four (pg. 1-1) - and has generally been followed for this writeup; the 'DECsystem-10 DECSYSTEM-20 Processor Reference Manual', AA-H391A-TK, July 1980, says two (pg. G-18).

See also

External links