(non volatile) RAM disk, looking for the cheapest storage chip - Page 1
Forum section: electronics / general

author: legacy
author_rank: Super Contributor
timestamp: February 01, 2016, 01:38:31 am
content: I am trying to add a storage device to my 68K board, I'd like to have something as big as possiblemy board has 5 slots, each slot is capable to address up to 16 Mbyte over a 32bit parallel buscurrently in use chipsDS1265Ychips, whose datasheet claims:fully static nonvolatile SRAMs organized as 1,048,576 words by 8 bits (1Mbyte)5 years minimum data retention in the absence of external powerData is automatically protected during power lossUnlimited write cyclesthe above PCB draft shows the initial idea where I planned to use four NVRAM, in the theory I have enough space on the each DIP socket to address 4 Mbyte per chip, but I can't practically find anything greater than 1Mbyte (I mean at cheap price, a NVRAM chip of 2Mbyte (1) costs too much), so the ram disk is going to be (1x4=) 4Mbyte of total storage size, just because I found 4 chips shipped for 50 euro (second hand, and they work fine).OK, so here we are with the topic questions: what do you suggest, guys ? FeRam ?Do you know a cheap FeRam chip, which comes with 3.3V/5V, 8bit data interface, 2..4Mbyte per chip ?All of this, at cheap price ? (say, "it's cheap", if it costs a quarter than Dallas price for their NVRAM)thanks(1) e.g.DS1270Y, 2Mbyteedit:ops, I had forget to underline:it MUST be non volatile, I mean able to retain information once switched off

author: legacy
author_rank: Super Contributor
timestamp: February 01, 2016, 02:47:49 pm
content: it seems the biggest FeRAM chip is sized no more than 512Kbyte

author: miguelvp
author_rank: Super Contributor
timestamp: February 01, 2016, 07:03:08 pm
content: Quote from: legacy on February 01, 2016, 02:47:49 pmCypress has bigger ones than that:http://www.cypress.com/products/nonvolatile-ram

author: legacy
author_rank: Super Contributor
timestamp: February 01, 2016, 07:41:39 pm
content: Parallel F-RAM Features, Density: 64Kb - 4MbI have to check their packages, as I can't handle the BGA

author: miguelvp
author_rank: Super Contributor
timestamp: February 01, 2016, 07:58:34 pm
content: Quote from: legacy on February 01, 2016, 07:41:39 pmI was thinking more the 16Mb one giving you 2MByteshttp://www.cypress.com/products/16mb-nvsram-replacement-battery-backed-sram-and-mramUnless you can combine several 4Mb ones to give you more.

author: C
author_rank: Super Contributor
timestamp: February 01, 2016, 08:11:56 pm
content: If this memory is not changing much, this might help.If you had a memory management unit you could use the dirty bit to write a block to storage.In place of a blind big memory block copy, you could do smaller what has changed copy.Dirty bit = block of memory has been written to.Dirty bit store is just an extra ram that does a read on every memory cycle and tacks on a modify write if WR active. This is where one bit in this memory = one block.If the true power off device has a block size, you could make the dirty bit size match.Not as simple, could be cheaper for larger memory size.

author: legacy
author_rank: Super Contributor
timestamp: February 01, 2016, 08:13:34 pm
content: umm theCY14B108Lseems interesting

author: miguelvp
author_rank: Super Contributor
timestamp: February 01, 2016, 08:39:57 pm
content: Would be 3V +- 20% be an issue?Also not very cheap (just read the OP) but I don't know your definition of cheaphttp://www.findchips.com/search/CY14B108L-ZS45XI

author: miguelvp
author_rank: Super Contributor
timestamp: February 01, 2016, 08:51:37 pm
content: Cool just making sure you took the voltage into account and that $40 was cheap enoughOf course the one I linked was the cheapest one with 45ns access, the 25ns and 20ns ones cost more.