RAM chip: Difference between revisions

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==Speed grade==
==Speed grade==


The number after the - indicates the speed (max time between /RD going low and stable data):
See [[memory speed]].
 
* 15: 150ns
* 12: 120ns
* 10: 100ns
* 70: 70ns
* 45: 45ns
 
Speed grade must absolutely be equal or less to replaced RAM chip.


==Replacement==
==Replacement==


Look for 5 volt, 32kB (32K x 8bit) / 256kbit SRAM (Static RAM) with the right speed grade (most today are 45ns, so any will do) in 28 pin SOIC package. Cypress, ISSI and Lyontek still make them, they go for about $2.50.
Look for 5 volt, 32kB (32K x 8bit) / 256kbit SRAM (Static RAM) with the right speed grade (most today are 45ns, so any will do) in 28 pin SOIC package. Cypress, ISSI and Lyontek still make them.


[[Category:Chips]]
[[Category:Chips]]
[[Category:Repairs]]
[[Category:Repairs]]

Revision as of 02:43, 21 October 2017

Sony CXK58256 120ns RAM

MVS RAM chips often fry due to overvoltage from a badly adjusted or failing cab power supply. It appears that the most common failure mode is the inability to write new data, resulting in errors during system self-test at the beginning of address ranges.

Basically, all NeoGeo RAM chips with "256" or "257" in their markings are 8-bit 32kB RAMs.

Pinout and cross-refence

To do.

Speed grade

See memory speed.

Replacement

Look for 5 volt, 32kB (32K x 8bit) / 256kbit SRAM (Static RAM) with the right speed grade (most today are 45ns, so any will do) in 28 pin SOIC package. Cypress, ISSI and Lyontek still make them.