Te St506 predated the st225 by about two years.? I have a few of the latter?
as they were free (RD 31 and also St250s RD32).? I prefered the RD52
Quatum drives much faster and more reliable.? I think I still have 10 or
12 of them.? And a bunch of BA42 boxes.
The ST250s I have some of the few remaining as they ran hot and
tended to fail without a lot of air.? That and RQDX2 and RQDX 3
controllers with formatting software XXDP) plus MSCP SCSI (CMD).
Primary use was one of the many Qbus PDP11s and a pair of
Qbus MicroVAXII as swapfile drives.??
Still use both PDP11 (primary is 11/73) and a bunch of MicroVAX mostly 3100s.
When I'm bored I fire up the PDP-8f for a dose of serious front panel.
The right way to handle large disks as most all are 512 byte is to treat a
physical sector as 4 logical so SPT can easily be 4 and then 16384
tracks with deblocking. NEver considered just using half a sector
even though they were cheap and plentiful.? Both efficient and
fast as then each sector read is usually a preread for the next 3.?
If you make it 32SPT you get a whole allocation unit 4KB) in the
buffer, obviously banked ram is needed to keep system size
large.? That and a write back timer to keep the file system clean.
However as mentioned a 1 or 2gb device is far bigger than CP/M can use
even with multiple loadable disks.? The largest compendium of CP/M
software barely fills a old school Cdrom even that has duplicates
of duplicates.? My largest system uses CF? a 128MB device in 8bit (memory)?
mode for easy interface.? Its partitioned in BIOS as 16 possible drives
with any 4 "on line" (61Kb system). and a loader program to use B:
through D: as any one of 15 not assigned.? Not one of those 8MB
partitions is fully used.? However they are organized with application
specific files like? one logical drive BDS C compiler, another
HiTEC C, and one for Pascal and so on.
The FAT approach is interesting but its nearly as a large as the whole
CP/M BDOS as it implements minimalist DOS. A dos within a dos.?
The BIOS seems to need the ZMC15 eprom for some of the low
level work.? Still digesting all of it.? However a thought that pops
up is a Z80 that runs PC Compatable at the filesystem level DOS
but has a full set of Z80 aps so that file transfers are DOS, even
better if a hierarchical files were doable.? It would be consistent
with the late 80s with people trying to get to better than CP/M or
maybe Unix.
I still build fast and high performing CP/M systems experimenting
with things like networking, supporting slave processors, and improving
performance.? Turns out very few system really exploited the possible
though the Kaypro 4/84, AmproLB+ for physically small and the
Compropro S100 crate offered things like RAMDISK, fast controllers
(DMA) and even a system multiplexer with 8085 to off load the
main cpu (z80 at 10mhz).?
Enough nattering on...
Allison
