|This is, as far as I am aware, a complete résumé of all of the Econet servers.|
Thanks to Owen Smith for additional information.
Level 1 The Level 1 server operated on a BBC B microcomputer with floppy disc and offered little more than a networked DFS emulation.
The Level 1 server only allows users to load, save, and catalogue files. There is no support for data file access and will not support the network facilities used by computers more recent than the Master 128.
Level 2The Level 2 server operated on a BBC B microcomputer with floppy disc and a 6502 second processor; or a Master 128 with second processor.
It expands upon Level 1 by offering various extensions over and above the earlier server - more commands, a directory structure, user level access (name & password), random access to files, etc.
Level 3The Level 3 server is virtually identical to Level 2 with the exception of harddisc support, as the Level 2 is limited to a maximum of 2 800K floppy drives. It is now possible to serve files from a 10Mb or 30Mb "Winchester" drive.
Note that a floppy drive is still required, for initial booting of the server software.
FileStore E01This is a dedicated machine based around a 6502 and housed in a Master Compact style box. It is a fairly competent server, but it seems quite lethergic. Perhaps the worst feature is that it only seems to want to work with a rather slow clock (1µS mark : 4µS space).
While gaining access to the server is rather a doddle (often little more than "open the flap and log in as SYST"), it is quite security-minded with respect to the users. If you create an empty file that is to be 2Kb long, the server will allocate space for the file and then blank the file (try it on a RISC OS machine and you'll get whatever 2048 bytes happened to be there previously!).
The server contains two built-in double-density 3½" floppy disc drives offering around 600Kb each. It can be further expanded with the addition of a 20Mb Winchester drive. It also offers a built-in printer server; plus automatic clock and termination - although the clock has a reputation for enabling itself even if there is a clock already operating.
The server program is supplied on a 64Kb ROM which contains a cut-down version of the BBC MOS plus the server code. Because of this, it is quick to start and no longer is there a need to worry about loss or corruption of the boot disc.
In essence, you could think of this as a dedicated unit that behaves much like a Level 3 server (with the ability to auto-boot, know the date, and format its own floppies) with the Printer Server thrown in too.
FileStore E20This is an expansion unit for the E01 (not E01S) which connects to the expansion port and provides a 20Mb "Winchester" drive for the FileStore. Housed in an identical style case, it contains a basic SCSI interface and the harddisc itself. The FileStore will detect the presence of the harddisc automatically.
FileStore E01SThis is practically identical in appearance to the E01, the primary difference being that the SCSI interface is now on the motherboard, hence up to four harddisc units may now be attached in a 'stack'. The firmware EPROM says it is the "Stacking FS", and the 'S' in the name means it is the 'stackable' version.
While the printer server does not offer much - it has been used to print to an Epson laser printer from an A5000. The SJ printer facilities may be all sexy and stuff, but the FileStore "just works" (TM!).
The on-board clock is much better behaved and keeps quiet if it isn't required.
FileStore E04S and E60SThese are the harddisc units which may be connected daisy-chain to the FileStore, in any combination, to offer a potential of 240Mb of storage (60Mb × 4 - quite awesome in those days).
As the SCSI interface is contained within the FileStore, the E40S and E60S boxes contain, basically, a SCSI harddisc and a small power supply unit.
Unfortunately the FileStore appears to require the message "(C)Acorn" to be present within a write-once maintenance control page of the harddisc. When my drive failed, I located a Rodime of the exact same type, but while the FileStore could 'see' the drive was attached, nothing would convince it to actually make use of the drive. I may try with a different drive later on, now that I have an EPROM programmer and could, if necessary, patch the firmware to not do this. But - hey - I'm getting above myself, it might be an enjoyable challenge for ARM code, but I don't feel that I'm up to speed with 6502 code.
Level 4Acorn's foray into serving from a RISC OS machine. It offers pretty much the same facilities as the FileStore, only it does it about 10 times faster. We can only wonder why they didn't think of pinching a few ideas from SJ's servers.
Level 4 operates as a multi-tasking application, but can (if necessary) work in a single-tasking mode.
Printer serverIn the days before the FileStore and the SJ servers, it was necessary to set a BBC micro to be a printer server. This was achieved through the addition of a "printer control EPROM".
As a historical note, this explains why much Econet stuff 'assumes' that the file server is station 0.254 and the printer server is station 0.235.
SJ Research FDFSThe FDFS (Floppy Disc File Server) was introduced more or less in tandem with the HDFS (described below). In a big to reduce the outlay of using SJ networking products, it offered enough ports to connect up to four double sided Quad Density floppies (1280Kb), though most people used Double Density (800Kb).
In common with all of SJ's products it provides a heirachical filing system, full user accounting, and a printer spooler - all based around a Z80.
There are probably as many of these in use as there are Level 1 servers due to the fact that you simply couldn't "bolt on" a harddisc in the future if your needs changed.
SJ Research HDFSThis was, for want of a better description, an unimaginable monster - requiring two people to lift it safely. The acronym means Hard Disc File Server - and as expected it offered originally a 20Mb harddrive with 20Mb tape streamer (for backup), this soon expanded to a range of options with up to 80Mb of storage and a 60Mb tape. The fan apparently sounded like an aircraft taking off.
The whole system was contained (is "contained" the right word?) on a huge circuitboard allowing the multi-threaded multi-tasking server code to make full use of the dual Z80 design which also happened to have DMA to 256Kb of RAM, along with 128Kb RAM for one Z80 and a further 64Kb RAM for the other Z80. This in the days when it was wow-factor to have a BBC Master with a whole 128Kb on-board!
Basically if you take Acorn's Level 2, upgrade it to be useful, have a few wet dreams and throw absolutely every idea possible in the 8 bit world into making a file server, while exercising as little self-restraint as possible, you would end up with the HDFS.
This is not the be-all-and-end-all of Econet servers, but it may represent the most over-the-top design based upon the Z80 in an actual retail product.
The HDFS was excruciatingly expensive at the time, but the only competition was Acorn's Level 2 (and, later, Level 3) so people bought it anyway. There are apparently very few of these (if any) still in use.
SJ Research MDFSThe MDFS offered it all, and then some. With the de-facto two printer ports, plus the capability to add four floppy discs and a chain of SCSI harddiscs, the hardware facilities were impressive.
The server side, just as impressive. 'Private' directories, good control over what users could/could not do, accounting, printer servers that could hold or spool printouts, and from the supervisor side - the ability to print a real-time report of what was going on at a level of logging you choose.
It is no lie that the MDFS was SJ's crowning achievement. In terms of Econet servers, nothing else comes close. I actually preferred to use my MDFS over Level4 because, well, because it was just so easy and so complete. In fact, the day my MDFS blew up was a bad day in my life. I have suffered various hardware failures before and while irksome, I've kept my wits about me and marched onwards. But the loss of the MDFS upset me as I doubt I'll ever find another one...
A compact circuit board with a single Z80, fully multi-tasking server software, serial and parallel printer spooling, heirachical filing system, the server just sat there and oozed confidence. My FileStore took one look at it and hid in shame.
awServerWritten (in BASIC!) by Alan Williams between 1989 and 1991, this is quite a reasonable attempt at emulating a FileStore on a RISC OS machine - and it multitasks!
There are some bugs, but as a free server it is invaluable for a quick'n'easy network. Several machines, Econet interfaces for each, a few bits of wire and a clockbox. Run awServer on one of the machines, away you go.
In use, there is little to differentiate awServer from an actual FileStore. Both look and feel the same (only awServer is a lot quicker due to running on a faster machine). It even uses the same format of "Passwords" file.
awServer is quite an achievement and while being aimed at the hobbyist, I can only wonder how it may have impacted sales of the Level 4 server. Migrate your files to a RISC OS machine, install awServer - you have sped up your serving and paid diddly-squat.
SoftMDFSJ. G. Harston took Alan Williams' awServer (in the year 2000) and twiddled it to behave like an MDFS.
I have not tried this software yet. When I do, I'll let you know how it behaves.
Advanced Level 4Released at the end of 1997, somebody somewhere still thinks there is commercial viability in Econet. This is an upgrade on Level 4 which offers many new facilities and makes it a little more like the MDFS. It does offer a 32bit NetFS (existing versions are 24bit) which speeds up communications across the network, though making it incompatible with 6502 machines and the MDFS. A 24/32bit version is planned.
It seems expensive (in my largely-ignored opinion), but luckily you can try before you buy: find out more at http://www.planet.demon.co.uk/.
I have not checked this link since 1999 - is this project still around? Does the 24/32 bit NetFS exist now?
NucleusNucleus (also known as Level 5 for a while) is the fileserver that sank two companies - Digital Services and Cumana (remember them?). It was to be an all singing all dancing server on a RiscPC using a DMA SCSI card and a custom filesystem (to get around the 512Mb disc limit). It was basically meant to be as sophisticated as an MDFS, but it foundered on the rocks of taking too long to write without making any money.
Some schools had beta test copies that they speak quite highly of. The original 32 bit NetFS work (which turns up in "Advanced Level 4" above) was done for Nucleus.
Looking at this, I can see a lot of similarity between this project and the "Advanced Level 4". I wonder if that evolved from the bits and pieces of Nucleus? If so, it's a shame they didn't keep the name, or go with something else atomic; as "Advanced Level 4" isn't a winning name.
And finally...It appears that other people have written their own servers. For a while I wrote my own, called "LevelFive" (gee, that's original!) which could serve a file if you asked nicely; along with user controls, soft-links (where "directories" could point to other places, a la Unix) and invisible files etc. I abandoned this after my network went 'bang' and I'm afraid the code appears to have been lost to time else I'd put it here.
Never mind, it was written in BASIC. These days I think I'd have done it in C.
Other servers (one also apparently called Level5!) seem little more than rumours, but I'm sure they exist somewhere. I do not plan to document any 'homebrew' server until it has been released into the wild... so, if you have written a server, give it the exposure it deserves!