The hard drive on our iMac (Intel Core Duo, Jan 2006) finally kicked the bucket. It was showing the infamous flashing question mark folder on boot. So in order for us to replace it we needed to open it up. Now, Apple didn’t allow the iMac hard drive to be easily replaced by the everyday user, but a quick search yielded this pictorial step by step guide on how to do just that.

The instructions are very good overall, but there are a couple of small tips which I’d like to include here for completeness.

Tip #1
In the step where the front plate is lifted off the iMac (”Remove the plate by lifting it away from you”), it should be noted that there are couple of metallic latches/hook inside the top corners of the iMac which are there to hold on to the rest of the machine.

If you lift the front plate up by force you will mangle these little parts. To release these, slide a stiff card of some sort under metal part and push up. Do this on both sides and the front plate will come off without a struggle.
- According to the iMac Service Manual you need an “Access card tool 922-7172″ which retails for $19USD, but a credit card or the common office magnetic access card will do just fine.

Tip #2
Once the four screws for the LCD are removed, you need to detach the LCD from the metallic shielding that is stuck onto the top of it before it can lifted and rested to the side.

To do this we find the Serendipity Software business card works wonders as it is thin and plastic, but I’m sure you can find another card in your wallet that will do the job just as well.

Apart from that the operation went very smoothly. The iMac now has no internal hard drive. It runs off an external firewire hard drive, which is kind of like a computer’s version of a colostomy bag.

Technorati Tags: iMac, hard drive

As many of you already know, the Signature Group editor in Workbench can import a variety of imposition signatures. However, we have encountered some files which contain impositions that are not as accurate as the numeric precision which is used in the file. This inaccuracy varies and and can often result in imported signature pages not grouping into grids, or grouped pages that are unable to be paired.

To compensate for that, the ability to round numeric values has been added to the importing of signatures. The precision in this rounding varies depending on how you import your signatures.
Note: Blackmagic stores all dimensions and positions in inches. So rounding precision is in reference to values in inches.

Importing with Selective Import Off

When Selective Import is off, dimensions and positions in the signatures are rounded to 4 decimal places before and after an attempt to group pages into grids.

Importing with Selective Import On

When Selective Import is on, the Signature Import Filter dialog is presented to let you decide which signatures you would like to import, with the option to perform a number of operations on them when importing. The Inclusive check box you see here deals with the rounding precision when importing.

• 
  When Inclusive is on, values are rounded to 3 decimal places before and after grouping.

• 
  When Inclusive is off, no rounding is performed at all.

Rounding can work for or against us, and Inclusive is certainly no guarantee that the pages will group and pair. Excessive rounding can actually result in pages not grouping or grouped pages not pairing when, for example, the inherent inaccuracy of the file is magnified, rather than reduced, by the rounding.

If pages are not grouping or pairing when importing, try the different options outlined above. If nothing seems to help, here’s a check list to go through. First, I would set the display unit of the Serendipity Client to points to increase the precision displayed. Also bear in mind that the Signature Editor only displays values to 4 decimal places.

Page Grouping Check List

• For pages to be grouped in a row, they have to have the same y position.
• For pages to be grouped in a column, they have to have the same x position.
• For pages to be grouped at all, they have to have the same dimensions.

Page Pairing Check List

• For pages in a grid to be paired vertically, there must be an even number of rows.
• For pages in a grid to be paired horizontally, there must be an even number of columns.
• For pages in a grid to be paired, head directions of adjacent pages (pages to be paired) have to be the same.
• For pages in a grid to be paired, every second row gap (pair vertically) or column gap (pair horizontally) must have the same dimension. In strict pairing (by using the Pair Pages button instead of the Pair Vertically or Pair Horizontally button) there must be no gap between pages you want to pair.

We will be looking into more intelligent methods for inaccuracy compensation for future versions of the Serendipity Client, but for now at least you know what goes on behind the scene.