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Rockbox mail archiveSubject: Re: SD Card BUS royalties on a new hardwareRe: SD Card BUS royalties on a new hardware
From: john cooper <john.cooper_at_third-harmonic.com>
Date: Fri, 10 Apr 2009 11:44:34 -0400 Paul Louden wrote: > Jonas Häggqvist wrote: >> >> No one said using SD is a bad idea. What *was* said, was that having >> *only* an external SD slot is a bad idea. We're suggesting you have >> some internal storage - which could be as little as 64MB - for storing >> Rockbox and the related files, and booting from. >> >> Do you really not see that having Rockbox on removable storage is a >> problem? >> >> The Rockbox build, themes, settings, highscores etc will be on the SD >> card, and you will have to copy these things back and forth or live >> with everything changing and having to reboot each time you swap the >> SD card. >> > Maybe as much as 1GB of internal storage would be good, if one idea is > to "share" music. If you have an SD card and no appreciable internal > storage, you can't actually share. You may as well simply swap players, > since there's no way to combine collections. If you have internal > storage, you can copy appropriately licensed music off their SD card, > then once you re-insert yours, add it to it. > The other issue which I had started to reply to was SD is becoming (perhaps has become) a viable choice for embedded flash usage. The issue being unmanaged NOR flash gets expensive as effective capacity increases. Moving to NAND flash has its own issues. Even if you aren't impacted by the loss of direct instruction execution with NAND, ECC becomes an issue. Not so much for the SLC devices as the required ECC strength is modest and as is the computational complexity of the ECC algorithms. MLC NAND is quite attractive from a low cost storage perspective. But it is a different beast and requires stronger error correction with the associated algorithms are (IIRC) at least O^2 dependent on data size resulting in very limited throughput in software based schemes. You probably can't find any currently manufactured flash <whatever> card which isn't MLC NAND. Flash controllers have pushed the error management issue into a hardware solution resulting in throughput essentially becoming a non-issue. So unless you are able to economically fit in NOR flash, NAND is going to be the solution. And except for the case of SLC NAND with software error correction you are looking at specialized hardware to deal with NAND management. My point here being is SD wraps up MLC NAND + hardware management into a unified solution at a mass market price point. SMD packaged surface mount SD devices as well exist. So in the case your widget is supporting an external user accessible SD media slot, a scheme will already exist to communicate with SD. Adding on-board SD would therefore pose no added interface requirements on the system. -john -- john.cooper_at_third-harmonic.comReceived on 2009-04-10 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |