03-07-2021, 04:59 PM
(03-07-2021, 03:33 PM)Arwen Wrote: Their are companies producing 2Mbit & 4Mbit SPI flash chips. Don't know how much they cost, but obviously using something smaller would be cheaper. Giga Devices, which makes compatible 128Mbit SPI flash in the PineBook Pro, (and probably other devices), makes such. May be not fast enough...
Note that USB 2 speeds are 480Mbit per second, about 30MByte per second maximum throughput. That's because it's a half duplex protocol, accounts for USB overhead and the original USB Block-only transfer was not designed for high speed storage. That's where UASP comes in to play. UASP can improve storage throughput noticeably.
So, no, USB 2 is no where near 100Mbytes per second of a eMMC or very low end hard drive.
I was thinking of something more like this: https://nz.mouser.com/ProductDetail/Winb...52Bg%3D%3D
Datasheet (page 6): https://nz.mouser.com/datasheet/2/949/w2...608377.pdf
If you see on page 8, the SOIC 300-mil should be hand solder-able - so quite viable for initial testing.
Apparently this can reach up to 50MB/s "continuous data transfer rate". Have a few of these and you can theoretically multiply the speed of the memory (as long as your controller can handle it) - so we should be able to max out USB 2.0 and look towards USB 3 speeds (in theory).
> Once we're up to about USB 2 speeds we are already about the speed of the eMMc currently shipped (hell some HDDs don't reach this), but if we can get to USB 3 speeds then I think it'll be quite future proof.
I was specifically thinking about something like the A64, which I believe can't really make use of 100MB/s. Even if it could - using USB 3 we should be able to beat that data rate anyway. And the goal would be to ultimately get the basics for an open source M.2 drive up and running (high speed comms, high speed memory management, etc).
