Using flash memory
|Wikipedia has more information about flash memory.|
There exist several threads about usage of Flash memory in the 68kMLA forums. This is a first attempt to collect information about this topic for convenient access.
CF cards are not intended for reliable long term use in the first place. You might better think of something like an improved ZIP drive to compare with. But CF cards are pretty cheap today, and the smallest number of _write_ cycles is about 10 k with a MTBF of more than a million hours (citation needed). The number of read cycles seems not to be a limiting factor in practical use. Flash memory storage devices for industrial applications are very long lasting and withstand hard mechanical shock as well as continuous vibration and an extended range of operation temperature. Because of the rugged design you will find flash memory storage devices in many industrial, military and aerospace applications, where reliability is crucial.
Flash memory devices are available in a lot of different form factors, like Compact Flash (CF) or Secure Digital SD or the newer variant SDHC. Even complete assemblies with SCSI, IDE/PATA or the most recent SATA interface are available as solid state disks. The latter outperform even recent harddisk drives in speed of reading access. As flash memory becomes more common as internal mass storage device in laptop computers, prices settle in an affordable. The price for a new solid state disk with a storage capacity of a few GB, well suitable for any vintage computer, is similar to the price of a recent medium range harddisk drive.
- If your system has no fan and you need it to be even quieter than a modern silent harddisk but with top performance, have a solid state disk or an industrial grade dual CF adaptor with two CF cards in striping RAID mode (level 0).
- If you do not need top performance a recent CF card or other flash memory device in an appropriate adaptor should do well in a vintage machine. In practical use recent CF cards perform very well. It usually is not recommended to use flash memory as Virtual Memory (citation needed).
As it comes to performance in a particular system it might be wise to do some tests before investing into expensive high end devices. As recent flash memory devices allow for high sustained read and write transfer rates compared to old harddisk drives, often enough a vintage Mac as a host system itself will be the bottleneck.
A Micro Drive for use as a replacement for a standard hdd would give you the benefits of a small footprint and low power consumption. A recent Compact Flash device usually outperforms any Micro Drive in seek time and transfer rate. The Micro Drive has the disadvantage of moving parts, like in usual harddisk drives. See also links concerning Micro Drives in "More Information".
Known options to connect flash memory to a vintage computer are listed below. It depends to the actual setup, which of the options is usable.
- CF card in a CF-PCMCIA adapter, used in a PCMCIA slot or a PCMCIA-SCSI adapter
- SD card in a SD-PCMCIA adapter, used in a PCMCIA slot or a PCMCIA-SCSI adapter (this is valid for SDHC in a SDHC capable adapter, as well as for any other kind of flash memory properly interfaced to PCMCIA. A lot of different adapters are available to fit various kinds of digital camera storage into a PCMCIA slot.)
- IDE/PATA Solid State Disk, optional IDE-SCSI adapter
- SATA Solid State Disk with SATA-PATA adapter, optional IDE-SCSI adapter
- CF-IDE adapter, optional IDE-SCSI adapter (this option depends heavily on the actual setup, many configurations will not work).
- Several kinds of SD/MMC or CF to 44 pin IDE adapters are available, to replace harddisks in 2.5" form factor (intended for laptop use, should work in other machines with 44 pin to 40 pin IDE adapter, as well). Adapters of this type usually resemble a slow solid state disk with the option to use and replace cheap consumer grade memory devices.
- CF-Floppy Disk adapter. This is a card reader for CF cards to be inserted into a Floppy Disk Drive.
- USB memory card reader, this option is only available for PCI equipped Macs with an USB card. Old world Power Macs might support USB 1. Driver software is available from Mac OS 8.6 to 9.2.2. There is no direct USB 2 support available for Macs with a classic Mac OS.
- Recent flash memory like SD, SDHC etc. might be adapted with an extra CF-adapter, as well as connectivity for recent computers might be supported with an USB adapter.
- Network Attached Storage (NAS) devices provide a LAN interface to a hard disk, typically IDE/ATA, SATA or USB 2. If your Mac has Ethernet and a working boot disk (even a Network Tools floppy) this is an option for extra storage. In some cases, this may be as fast or faster than a local SCSI disk. Used IDE NAS devices as well as recent network storage adapter devices can be picked up fairly cheaply.
Note: Some setups rely on the flash memory to be mounted as "fixed media", or else volumes will not be cold bootable. This is true for the PB 150 and PB 1400. Solid State Disks in harddisk form factor will work. Consumer grade CF cards usually will mount as removable media. Most CF cards for industrial use and many recent CF cards providing UDMA will work as fixed media. In doubt ask the manufacturer or check the page Flash Drive Test Results (contributions are most welcome).
A few pages dealing with specific aspects of flash memory already exist:
Discussions concerning performance and reliability of Micro Drives:
- Technical aspects in the use of Micro Drive devices.
- Testing performance and reliability of Micro Drive devices.
Several products to support vintage SCSI systems are available. Some are developed for this purpose and in production, currently. Some of the following links lead to product pages of products probably not in production any more. At least you will find full product specifications. Manufacturers might have some of the "end of life" listed items in stock, still. In case of demand contact the manufacturer and ask for a quotation.
If you have recent information about additional devices or availability, update this page, please.
- Adtron SDDS Cardpak™ PC Card Drive in 3.5" SCSI form factor for Flash memory in PCMCIA format ("end of life"). The drive is available in variations for use of one or two PCMCIA cards at a time. This adapter uses 5 Volt supply voltage, only. 12 Volt supply, as necessary for some PCMCIA flash memory cards, is provided by an internal DC/DC converter.
- Apdate S35P (=Adtron SDDS) SCSI Adapter in 3.5" SCSI form factor for Flash memory in PCMCIA format (available). The drive is available in variations for use of one or two PCMCIA cards at a time. This adapter uses 5 Volt supply voltage, only. 12 Volt supply, as necessary for some PCMCIA flash memory cards, is provided by an internal DC/DC converter.
- Adtron S35FA Flashpak® Solid State Flash Disk in 3.5" SCSI form factor
- Altec Compact Flash adapter in 2.5" and 3.5" format with two CompactFlash Cards Type I or II, uses raid level 0 for performance (striping)
- Artmix Compact Flash adapter in 2.5" SCSI format for use with a single Compact Flash card (available soon)
- Microtech Digital PhotoAlbum External SCSI PC Card Reader/Writer
- Microtech Digital PhotoAlbum i internal SCSI PC Card Reader/Writer in 3.5" SCSI form factor
- SCM/Microtech internal PCD-60B multi Card Reader offered at Primary Simulation Inc. This is an internal reader and has 6 slots: a single type II slot for ATA and hard drive cards and other slots for CompactFlash, SmartMedia, Memory Stick, Secure Digital, and xD cards.
- Reactive SCSI Bridge Emulators for use with Compact Flash cards, supports capacities up to 16 GB (emulates SASI, SCSI-1, SCSI-2)
- Spyrus External MCDISK-2 Media Card Drive for Flash memory in PCMCIA format, drive in 3.5" SCSI form factor (available)
- xpcgear SATA to IDE adapter converts recent SATA devices to the IDE/PATA interface.