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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.arch
Subject: Re: SSDs
Date: Tue, 11 Jun 2024 13:59:27 -0700
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On 6/11/2024 1:20 PM, Stefan Monnier wrote:
>> It has to have a substantial amount of RAM in order to coalesce writes,
>> after applying all those remapping/wear leveling layers. This write-back
>> cache has a limited amount of dirty buffers, preferably low enough that they
>> can all be flushed to persistent storage in case of power loss.
> 
> IIUC some don't have much RAM to speak of (they probably have some
> on-CPU cache-size RAM, of course) and lend some DRAM from the host system
> instead (accessed over PCI).  The technique is called HMB (Host Memory
> Buffer), and it's apparently quite popular.
> According to https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0229645
> the HMB is used mostly for the remapping table, while the write buffer
> used for coalescing is presumably some STL flash.
> 
>> The main task however is that when first turned on, the CPU will run
>> a substantial amount of burn-in testing, and then decide how many flash
>> pages are actually usable.
> 
> IIUC, another time-consuming task at startup can be to find the location
> of the logical->physical mapping table (since it can't be written at
> a fixed place in the flash, for wear-leveling reasons).

[ot] is there a way to create a flash disk that has the same protections 
as, say:

Dungeon Master
Technical Documentation - Copy Protection

http://dmweb.free.fr/?q=node/210