On Nov 20 2005, 0:55, Tony Duell wrote: I forget whether it's the mark that's longer than the space, or the other way round, but in essence the longer interval gives the hardware longer to respond and means you can run the network significantly faster. An Econet will run happily over a range of speeds, the upper limit being determined mainly by the length of the network, but for really short networks, ultimately the speed depends on the interfaces. clock I believe so. However, Field change Order No. 2020 says "Design error: Bi-phase network clock is 180 degrees out of phase with clocks generated by Econet Clock Boxes and E01S Filestores. Consequently the system fails to recognise the presence of an external clock when these are installed in large networks. This can cause unreliable data transfer." The fix given is to cut the tracks on the component side of the PCB, between IC26 pin 14 and SK10 pin 4, and between IC26 pin 15 and SK10 pin 5; then on the solder side link IC26-14 to SK10-5 and IC26-15 to SK10-4. I'm not quite sure what this implies for clock detection. Since the clock is free-running it won't remain phase-locked to anything else, let alone an external clock, so why that should affect the detection I don't know. Presumably something to do with the uneven mark-space ratio. similar to and at) header and adapter Well, the normal ACB4000 bridgeboard is actually SCSI, not SASI, but it's an early implementation and doesn't use the Common Command Set. All I said was "Yes" -- *you* wrote SASI :-) The winchester host adaptor board doesn't have the ATN line though. Actually, I was slightly off the mark. The 34-pin connector is for a box called an E20 containing a winchester adaptor (same as the Beeb one) and a 3.5" 20MB SCSI drive (native SCSI, no bridgeboard). It's basically a BBC 1MHz bus, but running at 2MHz like the one on a Master 128 or compact. Later types of filestore, called the Stacking Filestore, used SCSI disks without an adaptor board in the disk box. Those units have E01S instead of E01 on the front, product code AEH35 instead of AEH26, the bus connector is a standard 50-way Centronics-style connector carrying the SCSI bus, and the hard disk boxes would be labeled E40S, E60S instead of E20. The two digits gives the storage capacity, incidentally. Pretty ordinary SA400-interface double-sided 80-track single/double density half-height 3.5" drives, normally Sony F6 3W drives as fitted to Master Compact and similar machines including some early Archimedes or Citizen drives as fitted to other Archimedes machines. Some of the Citizen drives need a small mod (remove R61). Drives intended for PCs may or may not work because they may not respond correctly to DS0 and DS1. I thought Jules Richardson had scanned the user manual and service manual. Links 1 enable I/O IRQs 2 enable A15 adressing 3 enable 1?s network clock source 4 enable 2?s network clock source 5 enable network clock divide by 2 6 enable network clock divide by 4 7 enable network clock divide by 8 8 enable network NMIs 10 disable 0000-7FFF addressing 13 enable ROM latch There's more at the BBC Documentation Project, http://members.aon.at/~musher/bbc/econet.htm, and at The BBC Lives! site, http://www.nvg.ntnu.no/bbc/dir.php3?dir=doc Another place to look is http://beebmaster.co.uk/EconetHelp.html And of course the BBC mailing list (email majordomo AT cloud9 co uk or look for the archive -- presently down for maintenance -- at http://jonripley.com/8bit/bmlarchive/) and the comp.sys.acorn.networking newsgroup. -- Pete Peter Turnbull Network Manager University of York