Gordon's Tech

Friday, October 15, 2004

There's a simple explanation for hard-to-erase magstripes; they're the newer "high coercivity" type.

Old-style low coercivity magstripes are essentially the same material as is used for cheap ferrite cassette tape; they have a coercivity of only about 300 Oersteds. That means a 300 Gauss field is enough to wipe them. You can easily get that from a plain ferrite magnet, or an electromagnet you can make in ten minutes with some wire and a nail and a lantern battery.

Floppy disks score 720 Oersteds, higher coercivity tapes (DAT, 8mm video tape...) can score as much as 1400-odd Oersteds, and high coercivity magstripes are as tough as hard drive platters, in the few-thousand-Oersted range. Some high coercivity stripes apparently manage as much as 4000 Oersteds, though I think ISO Standard 7811 only specifies 3000. Magstripes are, of course, easier to wipe than a drive platter with the same coercivity, because you can lay a magnet right down on top of a magstripe; they don't have an aluminium casing around them like a hard drive.

My giant rare earth truncated pyramid fridge magnet has a real live 7000 Gauss field strength at its small end, which is way more than is needed to wipe any magstripe ever made. The part I grabbed is the big end, but that's quite likely to still manage better than 4000 Gauss.

Ok, maybe an immense magnet could do it. These are neat numbers to find. It turns out modern mag stripes are much harder to damage than the ones we had years ago.

Fujitsu ScanPartner 15C Flatbed Scanner Reviews at Shopping.com

Fujitsu ScanPartner 15C Flatbed Scanner Reviews at Shopping.com

A rather nice review -- I'd have said exactly the same thing. This old machine is a real problem for XP SP2 though. Key point is that a reliable document feeder is EXPENSIVE, and the home user doesn't value document feeders enough to pay what it costs to make a reliable one.

palmOne Tungsten T5 Handheld will not charge via USB cable

PalmInfocenter.com: palmOne Tungsten T5 Handheld Review

The USB cable alone will not charge the handheld from the computer, you must attach the AC cord.

One would hope they had a good reason for this decision.

Thursday, October 14, 2004

macosxhints - 10.3: Skip disk image checksum verification

defaults write com.apple.frameworks.diskimages skip-verify true

I did this. Does seem faster. Oddly my network drive mounts seem faster too, but I assume that's an illusion ...

iMac G5 - upgrading the bundled drive

iMac G5: "I recently purchased a iMac G5 from Amazon using the link from your site. I plan on upgrading the hard drive when it arrives and it appears to use a standard SATA 3.5' drive. Has anyone else upgraded the hard disk in their G5 and if so whose product did they use?

[Apple's 160GB drive for the 20' model is a Seagate ST3160023AS, the same drive used in some Power Mac G5 models. There may be faster drives available, however. -MacInTouch]"

RDC 1.0.3 is out (Mac to Windows remote control)

MacInTouch Home Page

Microsoft's free Remote Desktop Connection Client 1.0.3 enables Mac OS X (10.2.8 and up) to connect to a Windows-based computer running Terminal Services or Remote Desktop Services and work with programs and files on that computer. According to Microsoft, the new version includes the following changes:

Remote Desktop Connection Client 1.0.3 for Mac provides improved stability when you minimize the client window and when you copy and paste data from the client window to Macintosh applications. Stability is also improved for users of Mac OS X 10.3 and later, and when Remote Desktop Connection Client is used on Macintosh computers with PowerPC G5 processors.

RDC is one of Microsoft's most impressive works, one of the few areas they lead in.