jcf3703@ttardis.UUCP (chap flack) (10/06/89)
When I first put my system together (just this summer--yay) I called around for the most attractive hard-drive subsystem I could find and wound up with a promotional deal on a Seagate SCSI drive bundled with their own ST01 SCSI host adapter. I wasn't actually looking for SCSI at the time (anything would have done) but having bought it, the more I thought about it, the more I liked the idea of using just 1 slot for a standard interface which would let me add my hard drive and up to six more of all sorts of devices without having to find a slot for each one and find that they all need to use the same 4 IRQ lines, etc. But the realization of this vision seems to be blocked by various problems, some simply mechanical, others more subtle. Some may be solved by a different host adapter--this ST01 is worth about three pizzas and I'm not committed to keeping it. 1) The ST01 has a 50-pin header on the card, inside, for connection to the cable to the internal hard drive. This is great as long as I can put all my SCSI devices inside my system cabinet (fat chance). Seagate has announced a new version of the card which has an internal 50-pin header AND, on the rear bracket, the 50-pin connector specified in the SCSI standard; the two are just electrically parallel, so one can connect internal and external devices. This seems to me to be simply THE right way to do it. Does anyone else make a host adapter like this? 2) An ST01 can't really be a peer on a SCSI bus; it's really designed only to initiate transactions with things (drives, mostly) that only respond. For instance, the bit definitions in the control and status registers allow the host to drive ATTN and BUSY but not to read them; it can read REQ, C/D, I/O, and MSG, but not drive them. I don't have any application in mind where I would need my CPU to be selected by something else, but it might be nice to have a host adapter that could allow that. Someone must make such a thing. 3) The manual for my ST01 describes a hardware programming interface: the memory-mapping of the ST01 registers, their bit definitions, the function of the custom IC, etc. I'm sure other host adapters are different from a programming standpoint. I have a nightmarish vision of a marketplace full of SCSI peripherals, all electrically compatible and using the same SCSI protocol, but each one sold with driver software specific to the programming details of a particular host adapter--and therefore not compatible at all. Is somebody working on a PROGRAMMING standard for host adapters on ISA machines--like a defined BIOS interface? Someone has to be, right? The oversight seems just too gross. Hmm, I need to sum this up. What I'm hoping is that someone can steer me to a manufacturer of SCSI host adapters which a) have physical connections allowing easy connection of both internal and external devices; b) are capable of playing all roles in SCSI transactions (selecting/being selected); c) implement a standard 80x86/ISA/BIOS SCSI programming interface if such a thing exists or is proposed. Naturally I also need support for the BIOS INT 13H fixed disk calls (and a 4-pin connector for the usual AT front- panel activity light would be nice). It would be *very* nice if the INT 13H support included the usual BIOS multitasking hooks, i.e. INT 15H, AH=something, AL=90 (I think--don't have the book out) before waiting for a disk operation, and the INT 15H "post" call when the operation completes... I *think* this could be done by sending the command to the drive, releasing the SCSI bus, giving the BIOS wait hook, then having the host adapter interrupt when it is reselected by the drive, and the interrupt handler gives the "post" hook. *** Any information anyone can offer will be *greatly* appreciated! *** Also, anybody know how I should look for SCSI peripherals? Most ads I've seen for, say, scanners simply assume that you will buy their scanner and their controller card, and don't even mention what kind of interface connects the two. But it seems to me that the whole point of having a SCSI host adapter in my machine is to be able to go find SCSI peripherals and use them without buying more controller cards. Can anyone point me toward SCSI: scanners, tape drives, CD-ROMs--well, SCSI anythings, for that matter, I'd just like to know what's out there. <><><><><><><> Please respond via e-mail; ttardis, apparently because of space constraints, expires articles quickly, often before I get to read them. If anyone asks, I'll summarize to the net. Thanks! -Chap Flack ... uunet ! edsews ! rel ! ttardis ! jcf3703 (p.s. somebody please tell me if my .signature appears below....) ------------------------------------------------------------------------------- chap flack ... uunet ! edsews ! rel ! ttardis ! jcf3703 "i look around . . . i feel comparatively healthy." (steven soderbergh) ------------------------------------------------------------------------------- brought to you by the kind hospitality of the ttardis public-access people . . . any views expressed here are my own (or were when i wrote them)
sdm@hprnd.HP.COM (Steven Mueller) (10/12/89)
The SCSI Host Bus Adaptors (for PC/AT) that I know of generally fall into
one of two market segments:
high performance - 16 bit data path on ISA bus
on board dma - bus master
2-10 Mb/Sec
more $$$
generally used with high speed disks
low performance - 8 bit data path on ISA (or XT) bus
programmed io
~1 Mb/Sec
less $$$
generally used with any periph
Some cards include:
Vendor/card Perf
==================== ====
Adaptec AHA-1540A high
Western Digital
7000-FASST2 high
WDATXT-FASST low
Future Domain
TMC-830 low
TMC-860 low
Rancho Technology
RT1000 low
RT100XT low
RT-AT high
Trantor T128 low
Call the vendor for exact prices, but high perf cards will generally run in the
$300-500 range, low perf cards in the $100-300 range, depending on features.
I also suggest you check out the article in 2 October 1989 PC Week page 22
entitled "SCSI Host Adaptors Save Slots, Set the Stage for Multitasking".
Most of these companies have software driver platforms with drivers available
for many devices. My recommendation would be to check with the HBA vendors
to find out specifically which devices they support, and use that to choose
your devices.
Please keep in mind that the data above is generalized and I make no claims
about its validity :-) I want to stress again that, if you want multi-
connectivity to a single HBA today (for PC's), I recommend you talk to the
HBA vendors, because the periph vendors today are generally interested in
supplying a solution for their device only (and that's why a lot of them
bundle an HBA with their device). If you want any more info, feel free
to contact me.
Steven Mueller
Hewlett Packard "Ya babe, talk SCSI to me!"
916-785-4752
sdm%hprnd@hplabs.hp.comi13othor@vaxa.aud.auc.dk (torsten andersen) (10/18/89)
Disclaimer: I will NOT be responsible to any errors or misunderstandings
resulting from the following.
In article dated 6'th of October 1989 03:46:01 GMT Chap Flack asks about
anyone knowing something about SCSI Host Adapters (HA) for the ISA (Std.
AT) Bus.
I'm using an Adaptec AHA 1542A as HA. Among it's features are:
Internal and external SCSI Bus (not differential driven!)
Sector interleave 0 support.
LED connector for flash-light-fanatics.
Up to 10 MByte/sec. transfer speed for ISA.
Up to 5 MByte/sec. transfer speed for SCSI.
Support for more than 2 physical drives (via DOS driver).
Support for 2 std. floppy drives.
The AHA 1540A is the same, but w/o the floppy controller. But why not
ask Adaptec about specific information, they are very kind and helpful.
I don't think there exists a standard protocol for the ISA-SCSI comm. I
hope this will help You a little. (The cost of the AHA 1542A is around
$600, i think).
Torsten Andersen
Email: i13othor@vaxa.aud.auc.dknorsk@sequent.UUCP (Doug Thompson) (10/23/89)
In article <477@vaxa.aud.auc.dk> i13othor@vaxa.aud.auc.dk (torsten andersen) writes: > >The AHA 1540A is the same, but w/o the floppy controller. But why not >ask Adaptec about specific information, they are very kind and helpful. >I don't think there exists a standard protocol for the ISA-SCSI comm. I >hope this will help You a little. (The cost of the AHA 1542A is around >$600, i think). > Wyle Labs. has quoted me $267.00 for quantity one for the 1542A. -- Douglas Thompson UUCP: ..{tektronix,ogcvax,uunet}!sequent!norsk Sequent Computer Systems Phone: (503) 526-5727 15450 SW Koll Parkway !"The scientist builds to learn;the engineer learns in Beaverton OR 97006 !order to build." Fred Brooks