What would it take?

[RegisPhilbin]

What would it take to install and boot windows from a SD Memory card? I've seen memory cards up to 4GB and if you could RAID them to obtain a larger virtual drive, i believe it would be pretty darn fast.

Anyone have any idea what it would take to:

1) Use SD Memory card as a HD?
2) RAID SD memory cards together?


Regis

 

[SamurAchzar]

I don't know if such stuff is readily available, but it wouldn't be so complicated to build an ATA to SD bridge using a relatively simple processor. There's no reason you couldn't fully emulate an harddrive using that - and from there, sky's the limit.

 

[Peter]

Use a CompactFlash card instead. These do IDE straight out of the box, IDE-CF adapters are just mechanical items and inexpensive. Since every BIOS in this world knows how to boot off IDE, that just leaves Windows questions to solve. (Windows does not like to boot off removable media at all.)

 

[helpme]

Flash memory isn't that fast compared to hard disks.

High speed flash memory maxes out at about 20 MB/s, though it has very fast access times. Mixing reads and writes results in a signifigantly higher access time.

Single HDDs max out at about 97.4MB/s (sequential)

Considering operating systems tend to group boot files in a continuous portion of the disk, you will probably get good read speeds on bootup. Also, the hard disk has a large cache that may prove useful for small random files that might help with the random access delays(transfers at up to interface speed).

DRAM based storage on the other hand...

 

[helpme]

Originally posted by: Peter
Use a CompactFlash card instead. These do IDE straight out of the box, IDE-CF adapters are just mechanical items and inexpensive. Since every BIOS in this world knows how to boot off IDE, that just leaves Windows questions to solve. (Windows does not like to boot off removable media at all.)

If you use an CF to IDE adapter, you can install windows onto it just like an HDD. I've used a similar system to install Linux onto a cPCI system.

 

[helpme]

wtf... double post and quoted myself?

 

[Peter]

Originally posted by: helpme

Originally posted by: Peter
Use a CompactFlash card instead. These do IDE straight out of the box, IDE-CF adapters are just mechanical items and inexpensive. Since every BIOS in this world knows how to boot off IDE, that just leaves Windows questions to solve. (Windows does not like to boot off removable media at all.)

If you use an CF to IDE adapter, you can install windows onto it just like an HDD. I've used a similar system to install Linux onto a cPCI system.

Not necessarily - it depends on whether the CF in IDE mode identifies itself as a "fixed" or "removable" drive. The typical default configuration for off-the-shelf CF is "removable".

At the embedded-computing company I happen to work for, we are working closely with CF card vendors so our cPCI customers get "fixed disk" CF cards.

 

[helpme]

Interesting tidbit! I didn't know anything about that at the time, but it did work with an off the shelf consumer brand CF card when I tried it a while back (probably sandisk, it's been a few years). It's possible that the linux distribution we were using didn't care if the card was marked as "removable". Which Operating System(s) have you run into problems with the 'removable' status (out of interest for future reference)?

I don't remember what bridge chip we were using at the time either, it was for a Dual Xeon cPCI board... I can't remember the vendor at the moment either.

Is it just a flag in the Card Information area? Or is there a physical difference in the makeup of the card?

 

[SamurAchzar]

It's probably just a difference in one of the information descriptors the card sends to the host. I know SCSI works this way, for example (and ATA isn't so far removed from SCSI in terms of the basic commands, IIRC).

 

[phantom309]

Originally posted by: helpme

Originally posted by: Peter
Use a CompactFlash card instead. These do IDE straight out of the box, IDE-CF adapters are just mechanical items and inexpensive. Since every BIOS in this world knows how to boot off IDE, that just leaves Windows questions to solve. (Windows does not like to boot off removable media at all.)

If you use an CF to IDE adapter, you can install windows onto it just like an HDD. I've used a similar system to install Linux onto a cPCI system.

I've installed NT to a CompactFlash before. The problem is that flash memory can only do a certain number of writes - so you have to move the pagefile to a RAM disk or disable it if you want the CF to last. Other than that it worked fine, though it wasn't breathtakingly fast.