How can I trick my computer into treating the external drive as an internal not-plug'n'play, regular old drive?

April 20, 2004 3:04 PM

I put my old 10gb laptop hdd in a USB enclosure and bought a USB 2.0 pcmcia card. The speed is good enough that I would like to use the drive as a scratch disk for various programs I work with, but primarily Adobe Photoshop. Problem is, PS won't list it as an option in the scratch disks settings menu. It only lists the startup disk and the C drive, which are the same drive. How can I trick my computer into treating the external drive as an internal not-plug'n'play, regular old drive? Or just trick Photoshop. (Ver. 7, btw, and on a PC) Thanks.
posted by Grod to computers & internet (14 comments total)

If you can save your PS7 files directly to Windows' documents folder,
you can relocate the document directory from C: to the USB drive.

Just highlight the Documents folder, click Properties,
and "Move Target".
posted by Smart Dalek at 4:46 PM on April 20, 2004

OK, thanks. I guess I didn't phrase my question very well. The scratch disk (or cache) is a chunk of the hdd allocated to photoshop to use as virtual memory. If I give it the C drive the disk will fragment in no time flat. So I want to use the external drive. I never use the Documents (if you mean "My Documents") folder anyway. Thanks, though.
posted by Grod at 5:36 PM on April 20, 2004

I don't have photoshop to test this, but go to Control Panel/System/Hardware/Device Manager, open the properties dialog for your drive and go to Policies.

Odds are since it's a hot-swappable disk it's set to "Optimize for Quick Removal." Change that to Optimize for performance and enable write caching (you'll have to reboot).

Note that this changes the guarentees on the lazy writer and so you'll lose data if you don't "Safely Remove" the drive before unplugging it.

Let me know if this works, I'm curious now.
posted by j.edwards at 6:01 PM on April 20, 2004

Try here and here. I have never used photoshop and the links I've provided aren't much help. Maybe you can try editing the Photoshop preferences file by hand, if it's text, and manually set the scratch disk to the drive letter of your ext. drive (making a backup first of course). Also, make sure the latest patches have been applied to Photoshop.
posted by estey at 6:02 PM on April 20, 2004

j.edwards I followed your instructions, or tried to.
However the menu I arrived at had the following 4 checkboxes.


+-Options---------------------------------------+
|                                               |
|   []Disconnect                []Removable     |
|                                               |
|   []Sync data transfer        []Int 13 unit   |
|                                               |
+-----------------------------------------------+

Originally all four were checked. I unchecked removable and rebooted. The drive was no longer accessible through Explorer although Device Manager listed it as present. Next try I re-enabled Removable and disabled Disconnect. This had no ill effects but did not increase the number of options in Photoshop's plug-ins and scratch disk menu.
by the by, what's int 13 unit?
posted by Grod at 6:27 PM on April 20, 2004

Int 13 is the old-style BIOS disk access interrupt, so I assume "int 13 unit" means that windows will access the device through the legacy bios interface. Probably not useful for your problem.
posted by fvw at 6:37 PM on April 20, 2004

Yikes, you're on windows 98SE/ME, aren't you? My apologies.

Int 13 Unit means that the drive is under BIOS/INT13 extension (certain protocols for communicating with the drive) control. It seems like that should be left the way it is. (on preview: what fvw said)

Intuitively, it seems to me that "Disconnect" and "int 13 unit" should be mutually exclusive in the context of write caching and OS mount control (which is quite possibly what Photoshop is looking for). I will look for more information, but in the meantime I'd check on those links estey provided. Windows 9x is alien and strange to me.
posted by j.edwards at 6:44 PM on April 20, 2004

"Disconnect" means something else -- it means the device can release control of the bus while completing an operation. I don't think it has meaning for non-SCSI buses, but I may be wrong.

In any case, I suspect you are out of luck:

"1. Scratch disks must be fixed physical hard drives or partitions - no network drives or removable drives - Jaz, Zips or CD-RW - can be used." -- from here and elsewhere

As long as Windows chooses to mount the device as removable, which it will do so long as it's on the USB chain, you're going to be S.O.L.
posted by majick at 7:20 PM on April 20, 2004

Ah, thanks majick. The way I was thinking about "Disconnect" didn't really make sense to me given the other options.
posted by j.edwards at 7:23 PM on April 20, 2004

majick, thanks for the link. I can live with using the C drive as scratch, I'll just have to remember to defrag weekly. Not a big deal.
j.edwards, if you find anything, let me know. Seems like majick is right though, unless there is software to fool the computer into thinking a usb device is an IDE/ATA device, and I'm not certain how that would work.
Thanks again.
posted by Grod at 7:26 PM on April 20, 2004

If you use Partition Magic to add a small partition to the end of your drive, you could use that as the scratch partition to avoid fragging your primary.
posted by j.edwards at 7:47 PM on April 20, 2004

I'd be wary of tacking a partition on the end of the drive: any time you save by avoiding heavy write activity to the main partition, you're going to lose by having the head of the disk seek waaay to the end of the drive (and back again, to dip into swap and reference the main drive's FAT) whenever the scratch partition comes into play. It may very well even wind up being slower.

Unless you can get swap and/or scratch on separate spindles -- which was what this thread was about in the first place! -- partitioning doesn't really buy you anything in terms of performance improvement.
posted by majick at 8:17 PM on April 20, 2004

Very true. If you did some research into the drive geometry you could put the stuff on a different spindle, but with current platter density you'd be making a huge partition, and with a laptop drive it's probably only 1 or 2 platters anyways. So, nevermind that idea.

I know many IBM and Dell laptops (including mine) have a module that can accomodate an additional laptop hard drive -- you might also look into that if it's possible for your model.
posted by j.edwards at 10:30 PM on April 20, 2004

Is there anyway that you can mount the external drive as a network drive? That way it will emulate a local physical drive, and should trick photoshop into using it. Goto File, Map Network Drive, and browse for the external harddrive, hit enter. Make sure Reconnect at Logon is checked. It will place the external as a mapped network drive, open photoshop, and try to access it. Some versions of photoshop don't like "network" drives, if I remember.
posted by plemeljr at 10:33 AM on April 21, 2004