What advice do you have on the a2090?
Thomas VanNess Leavitt
Thom
chan Janin)
>How much is it worth, what are it's performance specs, etc?
>Thom
I own two of them !
List of pros and cons follows :
- the ONLY interface that can handle 2 ST-506 drives and 7 SCSI devices
- has rear SCSI DB-25 plug (MacInTrash compatible)
- the managing software is NOT user-friendly (text-input)
- the SCSI side does NOT read automatically SCSI devices' parameters
into their built-in ROM
- for ST-506 side : CANNOT HANDLE MORE THAN 8 HEADS ! (it should be max. 16)
- for SCSI side : all SCSI devices may not work properly with it
- you have to MOUNT (in startup-sequence) the partitions
- only the FIRST one from the FIRST drive is automatically mounted
- you canNOT autoboot on FFS, only "old" OFS is available
- other partitions can be FFS, hopefully !
- it does DMA very well, does not eat up cpu time at all
- it is RATHER slow : stock Amiga-2000B :
- with ST-506 120Meg/17ms at 256K buffer : max. 250Kb/s
- with SCSI 100Meg/23ms at 256K buffer : max. 350Kb/s
(talking about first partition, not FFS)
I personnally had to buy some because I wanted to use "old" ST-506 drives.
But I moved from ST-506 to SCSI... and now I have a VERY SLOW device...
but it works !
P-chan.
---
Pascal JANIN - Amiga maniac.. /// ..and Anime addict Forever...
STANLEY ELECTRIC CO. ///
R&D Group 71G, Japan \\\ /// "Yappappaa yappappaa Pi-i chan desu!"
Fax: 81+ 45-911-0007 \\X//
Email:NO! Fax/"F":YES! \/ "Kyoko-san ! Suki jaaa-- !!" >Godai-kun
Lee Kilpatrick
The biggest disadvantage I found it to have ws the problem of bus
contention. I am not sure of the exact story, but I believe it just
tried to transfer stuff over the bus without paying attention to
anything else using it. Anyway, the effect this has is that if you
use an appreciably fast drive, you can run into situations where it
cannot read anything from the disk and reports an error. This occurs
when you are using a hi-res 8 or 16 color screen, apparently because
these use more bandwidth on the bus in accessing the RAM.
I never saw this problem using my very old & slow ST-506 drives, but
when I got a SCSI drive, it was quite a nuisance. I don't know if the
speed factor came into play in the transfer rate from the drive or in
the architecture of the ST-506 as opposed to the SSI controller on the
2090 board.
On the newer mountlists there is a value called "MaxDataTransfer" or
something like that, the purpose of which may be to prevent this
problem from occurring... I don't know, when I was using the 2090 I
didn't know anything about this.
Sorry if this is somewhat muddled, I haven't slept.
Lee
Ed Smith
In article <83...@v785.stanley.co.jp>, ja...@v785.stanley.co.jp (chan" Janin) writes:
|>Path: e2big.mko.dec.com!pa.dec.com!decwrl!uunet!sun-barr!ccut!wnoc-tyo-news!dclsic!v785!janin
|>List of pros and cons follows :
..stuff deleted
|>
|> - you canNOT autoboot on FFS, only "old" OFS is available
..stuff deleted
|>---
|>Pascal JANIN - Amiga maniac.. /// ..and Anime addict Forever...
|>STANLEY ELECTRIC CO. ///
|>R&D Group 71G, Japan \\\ /// "Yappappaa yappappaa Pi-i chan desu!"
|>Fax: 81+ 45-911-0007 \\X//
|>Email:NO! Fax/"F":YES! \/ "Kyoko-san ! Suki jaaa-- !!" >Godai-kun
|>
I thought so to but after installing the 2.04 upgrade, just for yucks I
reformated DH2 (my 1st SCSI disk) with the new FFS, put workbench on it and
tried a reboot AND IT WORKED...
I been autobooting a V2.04 FFS DH2 from a A2090A for about a month now. I
assume it's because of some changed to the FFS in ROM. Can any C= folks
shed some light on why this works?
..Ed
A very happy A2090A owner.
Dave Haynie
>In article <83...@v785.stanley.co.jp> ja...@v785.stanley.co.jp (Pascal "P-chan" Janin) writes:
>>In article <1992Feb17....@cheshire.oxy.edu> lea...@cheshire.oxy.edu (Thomas VanNess Leavitt) writes:
>The biggest disadvantage I found it to have ws the problem of bus
>contention. I am not sure of the exact story, but I believe it just
>tried to transfer stuff over the bus without paying attention to
>anything else using it.
Nope. There are actually two problems, one of which goes away if you have
Fast RAM. They're both problems of determinism. The A2090 only has a 64
byte FIFO, and ST-506, being a low-level protocol (like floppies), there's no
way to tell an ST-506 device "stop sending data while I grab this here bus".
From the expansion bus's point of view, the Amiga bus is pretty non-
deterministic, there's no way you can know just how long its going to take to
acquire the bus after requesting it. The problem is that the Amiga chips can
stall a processor cycle for quite some time in heavy display modes (640 with
4 bitplanes, for example), and the DMA device can't use the bus until the
processor is finished with its cycle. So the A2090 would have its FIFO fill
up, request the bus, not get it quickly enough, and you'd essentially have
an overrun. The second problem is that, once the A2090 had the bus, it could
be stalled again and again if the DMA were targeted to Chip RAM.
The real flaw was that it didn't have provision to flow-control the SCSI bus.
ST-506 can't be controlled in this way, but it was rarely a problem (at least
if you had fast RAM), since most ST-506 disk drives were slow anyway. But a
fast SCSI drive on an A2090 would be death when you had lots of bitplanes up.
If you didn't, it worked fine, actually pretty fast too.
>I never saw this problem using my very old & slow ST-506 drives, but
>when I got a SCSI drive, it was quite a nuisance. I don't know if the
>speed factor came into play in the transfer rate from the drive or in
>the architecture of the ST-506 as opposed to the SSI controller on the
>2090 board.
SCSI was a problem because it was both faster and intelligent. The faster
basic transfer rates could have been a problem, but the intelligence was a
killer. Most fast SCSI drives buffer up track data in cache memory. When you
ask for a cached block, you get the whole thing as full speed. Your hardware
could, of course, control the flow over the SCSI bus, but the A2090s didn't.
>On the newer mountlists there is a value called "MaxDataTransfer" or
>something like that, the purpose of which may be to prevent this
>problem from occurring...
Max transfers could in some cases help the problem, though it really wasn't a
problem when the 2090 came out. One of the main slownesses of the SFS was that
it only asked for one data block at a time. FFS will try to ask for as many
contiguous blocks as it finds. If your device driver has a problem with more
than a certain number of blocks, you set the this max transfer value in your
partition data and the file system will be sure to never request more than
that.
>Sorry if this is somewhat muddled, I haven't slept.
No problem. Too much sleep makes you fat and boring. If had to sleep 6-8
hours a night I'd never get anything done...
--
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
{uunet|pyramid|rutgers}!cbmvax!daveh BIX: hazy
"I used to be disgusted, now I try to be amused" - Elvis Costello
Walter 'wasp' Mildenberger
In article <83...@v785.stanley.co.jp>,
ja...@v785.stanley.co.jp (chan" Janin) writes:
->[...A2090(a)...]
->List of pros and cons follows :
->
-> - [...]
-> - you have to MOUNT (in startup-sequence) the partitions
-> - only the FIRST one from the FIRST drive is automatically mounted
No, ALL first partitions are automatically mounted (Well, at least both my
MFM _and_ my SCSI-drive are mounted, dunno 'bout second ones on both types).
-> - you canNOT autoboot on FFS, only "old" OFS is available
That's only true for Kick1.3 - under 2.0 you CAN autoboot from FFS (actually
I *do* that all the time...)
-> - other partitions can be FFS, hopefully !
Certainly.
Regards
--
Walter Mildenberger, Morgenstr. 55, W-7500 Karlsruhe 1,FRG, (0721)385090
Sub/UseNet: wa...@chumly.ka.sub.org -or- Bitnet: UK...@DKAUNI2.Bitnet
A Smith & Wesson beats four aces.
Mike Farren
>
>I been autobooting a V2.04 FFS DH2 from a A2090A for about a month now. I
>assume it's because of some changed to the FFS in ROM. Can any C= folks
>shed some light on why this works?
Well, think about it a bit - if you don't have the filesystem in ROM,
then how are you going to use the filesystem to read the filesystem
off the LIBS: directory on the disk? 1.3 did not have FFS in ROM, so
when boot time came, FFS was not available. If the hard drive was
an FFS drive, you were stuck. Since 2.04 has FFS in ROM, it can use
it immediately, and so can autoboot from an FFS drive.
----------------------------------------------------------------------------
Mike Farren - no longer employed by Commodore. Still only my opinions,
and not those of any organization.
chan Janin)
>Hello !
>
>In article <83...@v785.stanley.co.jp>,
> ja...@v785.stanley.co.jp (chan" Janin) writes:
>->[...A2090(a)...]
>
>->List of pros and cons follows :
>-> - [...]
>-> - you have to MOUNT (in startup-sequence) the partitions
>-> - only the FIRST one from the FIRST drive is automatically mounted
>No, ALL first partitions are automatically mounted (Well, at least both my
>MFM _and_ my SCSI-drive are mounted, dunno 'bout second ones on both types).
I've read my A2090A too many months ago, so I made a mistake !
I think that effectively, FIRST partitions are automatically mounted,
but for ST-506 drives and the FIRST SCSI drive only.
2nd,3rd... drives should be ENTIRELY mounted manually.
>-> - you canNOT autoboot on FFS, only "old" OFS is available
>That's only true for Kick1.3 - under 2.0 you CAN autoboot from FFS (actually
>I *do* that all the time...)
Lucky you are !
I didn't have these 2.0 ROMs yet to make the test.
Let's say now you want to boot under ROMs 1.3 with a "ROM switcher".
How do you do ? A2090A won't boot.
Is there any trick then ?
>-> - other partitions can be FFS, hopefully !
>Certainly.
And boring-ly, mounted manually.
Is the A2091 far better ?....
(joke, maybe much better, but cannot handle ST-506 drives...)
>--
>Walter Mildenberger, Morgenstr. 55, W-7500 Karlsruhe 1,FRG, (0721)385090