It showed after some testing, that the maximum Interface speed, by not using the builtin Bridge Chip - is around 10.4Mbps (Mega Bits per second), This makes roughly 1.3MiBytes/s. The limitation is due to the CPU Speed which is running at 175MHz. At that speed though CPU utilization hits 100% - while the CPU is at this level - not many manipulations are possible fluently.
The Graphs on the right show this very nicely. On top - WLan, after that the Ether3 interface - server the 4GB Download was done from, and on the bottom the CPU Load in % during the file transfer. You can see very nicely that the CPU barely leaves the 100% mark..

I have noticed that through PPPoE (Bridge to the ether1 Device) 13.4MBits/s have been transferred. So - it seems the PCI-Bus is costing also some resources to the RB153 Board. 

 Check out the specs of the RouterBoard RB153.

It's actually a very neat little piece of hardware. Small, efficient, low-power. Only drawback is that the CPU is not able to power the full bandwidth the interfaces provide - thus if you really need 54MBit bandwidth - you should go over to the RB53x Series - which have the same CPU at 400MHz, able to handle the bandwidth.

• CPU: MIPS32 4Kc, 175MHz embedded
• Memory: 32MB SDRAM
• Storage: 64MB onboard NAND memory chip
• 5 x 10/100 Mbit/s fast ethernet ports with auto MDI/X
• 3 x MiniPCI Type IIIA/IIIB slots
• 1x 2.4/5GHz 802.11a+b+g High Power Wireless Mini-PCI Card (R52H)
• Onboard speaker
• Serial: One DB9 RS232C asynchronous serial port
• LEDs: Power, 3 LED pairs for MiniPCI slots, 1 user LED
• Power options: 11..60V power jack or IEEE802.3af power over ethernet (12V / 48V DC not for use with power over datalines)
• Power out: One 3V DC power output header, max. power output 500mA
• Power consumption: 3-4W without any addon cards. Max. 13W
• Dimensions: 160mm x 160mm (6.3in x 6.3in)
• Weight: 183g (6.5oz)
• Operating temperature: -20°C to +70°C (-4°F to 158°F)
• Humidity: 70% relative humidity (non-condensing)
• OS Support: RouterOS, GNU/Linux

You can have a view on the internals of mine. 

 In case you are repartitioning a drive - the UUID's (Universally Unique Identifier) get changed. This is more and more important as many devices today support hot-plugging or are external. You have several ways to identify the partitions. 2 of these are here. A simple way is the following:

$  ls -l /dev/disk/by-uuid/
 458b1af6-46e4-4980-8dab-ceaa2083459a -> ../../sda3
 6c80c066-08ad-4c22-9366-fe10ff8350e2 -> ../../sda2
 d18ad271-6831-4b83-980f-fe919ff65fd1 -> ../../sda1

will list you all UUID linked to the proper old known devices.
A call as Root of blkid will provide you the UUID of your harddisk.

$ sudo blkid
[sudo] password for jmertin:
/dev/sda1: LABEL="ROOT" UUID="d18ad271-6831-4b83-980f-fe919ff65fd1" SEC_TYPE="ext2" TYPE="ext3"
/dev/sda2: TYPE="swap" UUID="6c80c066-08ad-4c22-9366-fe10ff8350e2"
/dev/sda3: UUID="458b1af6-46e4-4980-8dab-ceaa2083459a" SEC_TYPE="ext2" TYPE="ext3"

 It's quite easy to do so. You just require fdisk and ntfsresize (Check your software repositories to have both installed. fdisk usually is).

With fdisk -l /dev/sda you can make a backup of start/end points of your actual setup. As long as you don't format the partitions - all is safe. Example output would be

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2550    20482843+   7  HPFS/NTFS
/dev/sda2            2551        7415    39078112+  af  Unknown
/dev/sda3            7416       10000    20764012+  83  Linux
/dev/sda4           10001       24321   115033432+   5  Extended
/dev/sda5           10001       10262     2104452   82  Linux swap / Solaris
/dev/sda6           10263       13041    22322286   83  Linux
/dev/sda7           13042       19121    48837568+  83  Linux
/dev/sda8           19122       24321    41768968+  83  Linux

In this case - delete partition 2 - and replace the end boundary of partition 1:

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2550      39078112+ 7  HPFS/NTFS

After that - just run ntfsresize with:

ntfsresize /dev/sda1

It will automatically adapt the ntfs journal and size informations to the new size and schedule a filesystem check for the next Windows XP Start.
Windows - after starting up - will want to restart as it has discovered new hardware (the bigger disk). After that restart - you're done.  

 Use the dmidecode programm. Without arguments, it will dump loads of data. To limit it - try this:

~$ sudo dmidecode -s system-manufacturer
LENOVO
~$ sudo dmidecode -s system-product-name
64585KG
~$ sudo dmidecode -s system-version
ThinkPad T61p

 Disabling Spotlight
- Launch Terminal and type the following: sudo nano /etc/hostconfig
- Navigate using the arrow keys down the following entry: SPOTLIGHT=-YES-
- Change SPOTLIGHT=-YES- to SPOTLIGHT=-NO- and save it.
- Next, you'll want to disable the index by typing the following in the Terminal:

 mdutil -i off /

And to erase the current Spotlight index, type:

mdutil -E /

Re-Enable Spotlight
- follow the same steps as above, but change SPOTLIGHT=-NO- to SPOTLIGHT=-YES-
- type mdutil -i on / in the Terminal
- Reboot, and Spotlight is back as usual  

 The issue with the Mac Mini 2,1 is that while it has an x64 processor (Core 2 Duo), it has a 32-bit EFI implementation. So getting a boot-loader to load an EFI loader is not that easy. Below are some links to help handling this:

• https://help.ubuntu.com/community/Mac_mini2-1
• Ubuntu 15.04 on Mac Mini 2,1 with EFI boot (2007 Intel)
• Installation/MinimalCD
• Mac OS X Lion: How To Boot A Linux Live System From An USB Drive & How To Update Any OCZ SSD’s Firmware
• (German) Ubuntu ISO-Image direkt vom USB-Stick booten
• Mac Mini 2007 needs a minimal EFI compatible .iso
• EFI boot Ubuntu 14.04 on a Mac without rEFInd
• mactel-boot hfs-bless code