★ HARDWARE ★ LECTEURS DE DISQUETTES ★ Inch high technology ★ |
| Lecteurs Externe - Siren Software - Inch High Technology (Amstrad Computer User) | Hardware Lecteurs De Disquettes |
Phil Craven gets into the driving seat for a spin around Siren's 80 tracks AS computer technology has developed over the years, becoming smaller in its old age, so the floppy disc has followed suit. The 8in disc quickly gave way to the 5.25in disc, and drives were reduced to a fraction of their original bulk. While 5.25in drives were losing height and 8in discs were seeking work as frizbees, two smaller floppies were introduced -the 3in, with which we are all very familiar, and the 3.5in. The main difference between the two, as far as we CPC users are concerned, is that our drive mechanism is 40 track single-sided, so we have to turn the discs over to use both sides, whereas the 3.5in is 80 track double-sided - 80 tracks per side, and the disc never needs turning over. Yet even today, new and expensive computers come on to the market with built-in 5.25m drives. We could be tempted to think that the 5.25in is the better device, but they are only there because the older computers had them, and because a lot of software already exists on 5.25in discs. On the right tracks While both sides of the 3.5in disc are used for data storage, there is only one directory, so to the user it appears as though only one side of the disc is used. Due to the use of ultra-modern surface mount technology, the Siren 3.5in drive is only an inch high. The unit measures 4in x 6in x 1.25in and sits perfectly on top of the internal 664 or 6128 drive. A power supply and a drive cable for the 464,664 or 6128 are supplied. This all sounds pretty good stuff, but the more observant will have noticed that I referred to "normal 80 track formatting" - and we don't have 80 track formatting on the CPC, normal or otherwise. Since the CPC's drives are 40 track mechanisms, the software we have for formatting discs-CP/M Plus Disckit3, for example - will only format 40 tracks, even on an 80 track drive. Some commercial disc utilities will format 80 tracks, but Amsdos will only recognise 40 of them and continue to give 178k per side. To get the full capacity out of Siren's 3.5in drive another disc operating system is needed. CP/M won't really do, since most commercial programs run under Amsdos. In use, each system is invisible to the user -SAVE, LOAD and CAT operate normally whether the 3.5in disc Amsdos format or the new system's format. The Siren drive is designed and configured as drive B, but by changing the position of its drive select switch it will operate as drive A on a 464. However, the CPC disc interface DOM will still be needed by 464 owners and, since all CPC disc software is on 3in disc, it would seem pointless to use the 3.5in as drive A. With up to 880k of storage space and only one directory, the usual 64 directory entries would not be enough. Both Rodos and Ramdos overcome this by allowing a selectable number of directory entries, such as 128 or 256. I haven't mentioned the make of the drive. This is because Siren will supply either the NEC or the Mitsubishi mechanism, depending on which is in stock at the time. The drive is described as one megabyte, which would imply that it has 1024k of storage capacity. But that is its unformatted storage capacity. Whether or not 1024k is realised depends upon the constraints of the system's hardware and software. In our case we can only get 800k on 80 tracks, which is done by increasing the number of sectors per track from the usual nine sectors to 10. Most computers never realise 1024k on a 1 Mb drive after formatting. This 3.5in drive is the first to be sold specifically for the CPC. To be honest, until I saw and tried it I wasn't at all bothered whether one was available or not. I was perfectly happy with my 5.25in for backups and archives. But this little cutie has stolen my heart.
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