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2 Presentation and installation.
After having presented the last Compact flash from SanDisk, and explained how to use it as a hard drive (also called SSD), we'll see what it's worth compared to a last generation hard drive, and especially what influence it can have on machine performances.
In order to do so, we will compare two clean Windows installation, strictly identical, respectively installed on our hard drive and on the Compact Flash (hard drive modded)
Test Machine:
 Abit AN7 (chipset Nforce 2)
Barton 3200+
1 Giga of DDR Corsair
Maxtor 250 Giga Max + 10 hard drive
Compact Flash SanDisk Extreme IV 8Giga
Adaptor CF -> IDE MESA
Serillel 2 Abit (from NF7S V2.0 bundle)
Presentation of the Compact Flash memory:
SanDisk's last generation of Compact Flash cards, with the arrival of the 8 gigas Extreme IV, marked the pace with transfer rates twice as fast as the older generation. The card we're going to use displays a transfer rate of 40Mo/s in read mode, no less. True IDE compliant, it intergrates a contoller supporting Ultra-DMA 4 mode, allowing transfers rates up to 66Mo/s.
Associated with a small Compact Flash to IDE adapter, it will give you the equivalence of a hard drive without any moving parts, which corresponds perfectly to the definition of a SSD. However, the adaptator will need to be Ultra-DMA compatible, to obtain optimal performances from the Compact Flash using Ultra-DMA 4 mode.
Compact Flash cards indifferently accept to be powered in 3.3V or 5V. The adapters supply them with 5V, which should be enough, in theory. Unfortunately, the Extreme IV will chose otherwise, all transfers under Windows were revealed impossible, in relation to stability issues not known yet, when connected to the motherboard using a 80 pins IDE cable. The use of a 40 pins IDE cable allowed use to make it run in Ultra-DMA 2 with 33Mo/s maximum transfer rates. Howeven, unstability isues still remained, as Windows (installed on the CF), would downgrade the working mode to PIO much slower.This problem only occurred for an IDE connection, with Sata, the card working fine with 5V and 3.3V.
We have no clear explanation on this issue. We tested the adapter and CF in 5V, on different motherboards based on different chipsets (Nforce2, Nforce4, Nforce6, P35, 965P), with each time the same problems. SanDisk declined to reply clearly on this point as yet; and we are still waiting for an answer which may help understand.
The solution consists of powering the adapter, not in 5V, but in 3.3V with the help of a wire connected to the 5V pin of the adapter's minimolex, at one end, and , to one of the 3.3V wires from the ATX cable at the other end .
The adaptor, with 4 drilled holes and needing bracings to be fixed to the unit, isn't the easiest to integrate! Nevertheless, a simple solution allows it to be solidly held in place in an unused floppy drive space, using string, or, in this case, a shoelace. The Compact Flash is then easy to insert or retrieve by the front of the unit.
General public Compact Flash cards are usualy recognized as removable hard drives under Windows, the Extreme IV being one as well. Indeed, only SanDisk's industrial series are recognized ase fixed disks under Windows. In reality the removable or fixed state of the cards depends on a flag located within the firmware, modifiable under msdos environment using some rare programs.
Modifying the default firmware, as done on our extreme IV, is a delicate operation not to be taken lightly. However, this step is essential in order to successfully install Windows on the card.
We will see how it goes on against a Maxtor reaching easily 65Mo/s in read mode. The struggle promises to be unequal, and will not only depend on the transfer rates as it was the case up to now. Who will win between fast access time and fast transfer rate?
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