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APPLE II DEVELOPMENT FORUM CONFERENCE LOG
Tuesday, May 1, 1990  10:00 p.m. eastern time
Topic:  Operating Systems
Forum Leader:  AFL Dyfet

AFL Dyfet  Good evening and welcome to the Apple II Development Forum. 
           Tonight our topic
AFL Dyfet  is Operating Systems.  We will be using PROTOCOL.  This means that
           if you have
AFL Dyfet  a question to ask, enter a '?' on a line by itself, and if you
           wish to comment
AFL Dyfet  on the question being asked, enter a '!' on a line by itself.  You
           will each be
AFL Dyfet  called in turn.  I believe Keith had the first question....GA
           Kieth...
KeithR4 No questions yet, GA
Coach101   I think Keith asked a question before the conference started about
           what was meant by
Coach101   channels?  If you are a certified developer you ave access to
           AppleLink (Apple Edition) and can ask
Coach101   very detailed programming questions in an official manner (i.e.,
           channels).
AFL Dyfet  GA Keith...
KeithR4    Thanks for answering
KeithR4    ga
AFL Dyfet  Okay, I believe Parik now has the floor...
AFA Parik  has anyone here written a macro program?  if so, whats the best
           way to 
AFA Parik  intercept key-calls?  ga
AFL Dyfet  GA Keith...
KeithR4    What language and development system are you using Parik?
AFA Parik  asm65816
KeithR4    Apw or Merlin?
AFA Parik  orca :)
Coach101   PRIZM or EDIT
KeithR4    Sorry can't help you there. ga
AFA Parik  rose (heh)  ga, never mind
AFL Dyfet  :) Okay, getting back to your question, I believe there is some
           sample source
AFL Dyfet  on how to steal keyboard interrupts from C...you may wish to start
           by looking
AFL Dyfet  at that.
AFA Parik  ok!  thanks
AFL Dyfet  Okay, Coach now has the floor...GA Coach...
Coach101   My question has to deal with intermodule communication...
Coach101   Specifically, if you have a driver, a permanent init, and a Cdev
           that comprise some variety
Coach101   of service support for an application program, how can the init,
           driver, and Cdev communicate with
Coach101   each other.   ga
AFL Dyfet  My first thought is message center...GA Dave...
Dave Lyons Use MessageByName and MessageCenter to publish an
Dave Lyons address that the others can look up & then call.  (Several of
           your
Dave Lyons compenents can publish their own hooks, or invent your
Dave Lyons own variations.  I'm using this approach in a
Dave Lyons not-quite-released-yet Nifty List, and it works well.  Now, Matt
           has another approach:  (GA)
AFA JoeyS  <drooling over the thought of a new NiftyList...>
Matt DTS   Dave (and Dave)'s method is well and good, but if you really have
           a GS/OS driver installed, it's not
Matt DTS   necessary.
Matt DTS   If you have a GS/OS driver (which, by the way, is absolutely the
           most intelligent way to control
Matt DTS   hardware), you make it so that the driver handles ALL the hardware
           requests through DControl, DStatus,
Matt DTS   DRead and DWrite calls.  If you need to set default parameters
           (for example, default color on a color
Matt DTS   printer), use DControl.  If you need to know if the printer's
           online, use DStatus.
Matt DTS   Drivers are present before CDevs and Inits are loaded.  If the
           driver doesn't find it's hardware, it
Matt DTS   will be unloaded by the Device Manager.
Matt DTS   So:
Matt DTS   Get a unique Device ID from DTS for your driver, so you can find
           it with a DInfo scan just like you ca
Matt DTS   (can) currently find servers or SCSI hard disks.  Have your
           CDev/Init search for the driver and call 
Matt DTS   it to do all the work.
Matt DTS   (If you want to use MessageByName to indicate that the driver's
           there and what it's device number is,
Matt DTS   that's dangerous - new drivers can be installed at any time so you
           should search every time.)
Matt DTS   It's simple and lets the driver do all the work, which is what you
           really want anyway.  GA.
Coach101   Matts approach is much closer to my requirement...
AFL Dyfet  GA Dave...
Dave Lyons So, how does the CDev communicate with the permanent init part?
Dave Lyons (Or doesn't it need to anymore?)
Coach101   But, can I have drivers that have no hardware associated with
           them?  e.g., they do funny things
Coach101   with an existing driver (AppleTalk for example)?
Matt DTS   No.  Drivers deal with hardware, not other things (especially not
           other drivers).
Matt DTS   You can, however, write your own AppleTalk protocols and get them
           loaded (if you like).
Coach101   But, I could have a device driver that talked to the AppleTalk
           manager right?
Coach101   Wrong...   Bad, dumb, studid idea!
Matt DTS   You can have a device driver that makes AppleTalk calls ($E11004,
           or whatever).  You can't have a
Matt DTS   device driver that makes calls to the AppleTalk drivers.
Andy Stein Burger Bill is writing a Hewlet-Packard driver at 300 DPI!
Matt DTS   You can write a driver that communicates with the supervisory
           drivers, but there isn't an AppleTalk
Matt DTS   supervisory driver.  (Protocol?)
Coach101   Thanks for the ideas, I will mull them all over and see what pans
           out..   ga
AFL Dyfet  Okay, I see that Marty is next...GA Marty...
AFL Marty  One of the members of AOL is having some difficulty with his hard
           drive....
AFL Marty  and I said that I'd ask this question here tonight...
AFL Marty  The member is using a SCSI hard drive with the DMS SCSI card
           ....
AFL Marty  (DMA SCSI)...
A2GS       DMA
AFL Marty  (thank you)
Matt DTS   (the GMTA SCSI card)
A2GS       ABCD
AFL Marty  and he is getting what sounds like the same unclaimed interrupts
           errors...
AFL Marty  that I've heard about before.  He is using an internal modem...
AFL Dyfet  Is he using the new SCSI drivers?
AFL Marty  Is there some way to work around this problem?
AFL Marty  Yes, he uses the new drivers.
AFL Dyfet  GA Matt...
AFL Marty  GA
Matt DTS   1) Using the new drivers is not enough.  He must use the INSTALLER
           that came with the card to install
Matt DTS   the modified GS/OS required by the new drivers/manager.
Matt DTS   2) When using the new OS, >64K interrupts is not a fatal error. 
           It will still ask you to "restart"...
Matt DTS   ...but if you press return, you'll be returned to the application
           with no ill effects.
Matt DTS   3) (off-chance) When using the new drivers/managers with the OLD
           SCSI Card (Rev. C), it's vital that
Matt DTS   you have proper termination - one terminator on the first and last
           device on the chain (or just one if
Matt DTS   you have just one device).  The old manager would let you get away
           with bad termination; the new one
Matt DTS   does not.  Take it from someone who watched SCSI have a party on
           his data.
Matt DTS   GA.
AFL Marty  Thanks for the info. GA
AFL Dyfet  Okay, I see that Keith has the next question...GA Keith, you have
           the floor
AFL Dyfet  now.
KeithR4    Is there any Pascal sample source code for doing list controls?
AFL Dyfet  GA Matt...
KeithR4    I'm using TML Pascal II and I can't seem to get a list control to
           work at all. 
KeithR4    ga
Matt DTS   Do you mean lists or the new 5.0 Extended List Controls?
KeithR4    either
Matt DTS   List Controls are easier than lists.  We haven't released any
           samples, but we will be within the next
KeithR4    I tried the normal lists first.  Didn't try the extened.  I nedd
           to create it
KeithR4    on the fly ga
Matt DTS   month or so.  Some will also be in the final Toolbox Reference
           Volume 3 from Addison-Wesley.
Matt DTS   (GA)
AFL Dyfet  GA Dave...
Dave Lyons Keith, do you want the list in a regular window, or inside a Modal
           Dialog?
Dave Lyons And, question 2, what went wrong when you tried it?
KeithR4    In a regular window ga
KeithR4    When I selected an item all of the items became garbage
Dave Lyons Okay, so it showed up correctly to start with, but
Dave Lyons when it tried to redraw later, the item text was all screwed up,
           right?
KeithR4    That's correct
Dave Lyons The strings for the items have to *stay* in memory where they were
           when you fed them to the
Dave Lyons list manager...sounds like you made a *local* array of strings,
           maybe, so they went away?
KeithR4    Do I need to do some handle locking?
Dave Lyons Are your strings in a handle?
KeithR4    Yes, they may have been local variales.
Dave Lyons (I mean, one you specifically allocated?)  Or what?
KeithR4    No, they are not in a handle, should I allocate one?
Dave Lyons Locals sounds like a very good bet--make 'em global or otherwise
           long-lived, and life will be good.
KeithR4    Thanks, done.
Dave Lyons (No, there's no special advantage to having 'em in a handle...you
           still have to have them somewhere
Dave Lyons to put them in the handle anwyay....)  ga
AFL Dyfet  Okay, Parik has the next question...GA Parik...
AFA Parik  will gs/os load cdas into special memory if bit 12 is not set in
           the omf field
AFA Parik  and will gs/os purge at least level 3 before running prodos 8? 
           ga
AFL Dyfet  GA Matt
Matt DTS   ExpressLoad (and perhaps the System Loader, not sure) always
           attempts to load non-special memory
Matt DTS   before using special memory.  If no special memory is not set, it
           will be allowed but not preferred.
Matt DTS   2) No.  GS/OS asks for the P8 memory and if some stuff needs to be
           purged to get it, it will be purged
Matt DTS   to get it.  It doesn't go around kicking out people's dormant data
           for thrills.
Matt DTS   (GA)
AFL Dyfet  GA Dave...
Dave Lyons Checking, but I don't think CDAs (when loaded by the system) get
           to use special memory even if
Dave Lyons no regular memory is available.  That's the flag on InitialLoad,
           right?
AFA Parik  i allocate a direct page in my Cda and it must be left after cda
           is exited. i
AFA Parik  use $4115 as memory-bits, and it doesn't get purged before running
           p8.  :( 
WinkieJim  Would prevent using P8 programs if they were loaded into special
           memory
Matt DTS   The memory manager will purge your handle if it's in special
           memory to get it for P8 - if it can.
AFA Parik  ga, i just have a key for disposing DP memory inside program. 
           kinda messy.
Dave Lyons Ah, but it would
Matt DTS   It can't purge locked blocks, for example.
Dave Lyons purge levels 3 and 2 first, before getting rid of his level-1
           blocks in bank 0.  Are you leaving
Dave Lyons that page there while not in your CDA on purpose, or are we just
           trying to explain the results
Dave Lyons of a bug?
AFA Parik  no, the page is used by a background interrupt.  
Dave Lyons Hmmm....
AFA Parik  (after exiting CDA).  it uses Memory Attributees of block may be
           moved or
AFA Parik  purged, and purge level 01.
WinkieJim  That's a no-no...I think
AFA Parik  I've used the WHERE utility of Prosel-16, and the PURGE.MEM. 
           It'll get rid of
AFA Parik  it.  But gs/os won't!  :(
Dave Lyons You need a way to shut that down nicely before P8 launches.
AFA Parik  ga anyways, message-base discussion is better.
AFL Dyfet  GA Winkie...
WinkieJim  Is there any way you can have your interrupt routine allocate the
           direct page 
WinkieJim  itself when it's called so you don;t keep the direct page all the
           time?
AFA Parik  good idea!  
WinkieJim  Just a suggestion gs
WinkieJim  ga
Coach101   You cannot use the MemoryManager at interrupt time...  Right?
AFA Parik  wait, that won't work.  the sound tool uses a direct page also and
           is left on
AFA Parik  :(  ga
Matt DTS   (Wrong.)
WinkieJim  Sorry just a thought...
AFL Dyfet  GA with your comment, A2...
WinkieJim  (i usally just save a few bytes on the direct page and put them
           back when i'm 
WinkieJim  done...I know: very dangerous.
A2GS       Without offending Matt,  :)  can you have the sound tools generate
           interrupts
A2GS       which are vectored to your sound interrupt handling routine which
           allocates
A2GS       or rather sets the DP to your address?
A2GS       Of course the problem then is resetting the DP.
AFA Parik   yes, but the sound tools need a direct page!  
AFA Parik  i think i'll leave the sound tools off and try replacing $E1/002C.
            ga with the
AFA Parik  next q
A2GS       Oh, I see...never mind I thought you meant that the sound tools
           needs the DP
AFL Dyfet  Okay, I believe Andy has the next question...GA Andy...
Andy Stein When I use System 5.0.2 with my Vulcan 40 Megabyte hard drive,
           every once in a
A2GS       during an interrupt.   (A2GS<---SMACK)
Andy Stein while, I find all my files strewn about the directory, in no
           particular order.
Andy Stein It seems to occur after I've booted a System disk that does not
           have the Vulan 
Andy Stein driver on it.  Also, why won't some Prodos 8 and 16 programs run
           properly on it
Andy Stein ?
Andy Stein ga
AFL Dyfet  GA A2....
A2GS       You probably have the FINDER info files on the same sys. Disk
           which contains
A2GS       your Vulcan Drivers and when you boot up another disk, the Finder
           can't "FIND"
A2GS       the files.  I Think?  :)   GA
AFL Dyfet  GA Matt...
Matt DTS   Not probable.  The Finder only stores info files for a volume on
           that volume, not other volumes.
Andy Stein Even after, when I boot up with Vulcan, the files are still messed
           up.
Matt DTS   It doesn't, for example, put any information about your hard drive
           on a floppy, or vice versa.
Matt DTS   "strewn about in no particular order"
Matt DTS   Lemme point out that files on ProDOS disks *aren't* in any
           particular order.  The Finder will always
Matt DTS   sort them by some criteria, but other directory listers (ProSEL,
           APW/ORCA, BASIC.SYSTEM) don't, so
Matt DTS   they'll seem to be in some weird order.  Is this what you're
           seeing?
Matt DTS   (ga)
AFL Dyfet  GA Head...
Andy Stein I mean, the files aren't in the visual order that they were
           originally in.
HeadCase   Could it be you have the preferences set on one finders not to
           save finder info?
Andy Stein For example, the AppleWorksGS is moved from the top to the bottom
           left, the
Andy Stein Xenocide from the bottom to the middle.
Andy Stein (On the main directory.)
A2GS       That's what the Finder files are used for (among other things)
AFL Dyfet  Coach...
Coach101   Finder defaults come from the disk that you boot from....   
Coach101   The placement of files on the desktop (if you drag
Coach101   files to the desktop) come from the device containing the
           files....  
Andy Stein Usually PD disks mess it up, like Bouncing Bluster, and that
           Tertrisosas game.
Coach101   This can get very confusing if you boot from multiple disks into
           the Finder...
Coach101   Could some combination of this be the difficulty?
Andy Stein Yes, Coach, that's exactly what I mean.
A2GS       I know that...but it is possible (although far fetched,
           admittedly) he may have
A2GS       accidently copied the finder files to his sys. disk.
Andy Stein Some disks only run from their own version of the Finder, and not
           my hard
Andy Stein disk's.
A2GS       Only thing I can think of...that's why I'm so stubborn   :)
sidley     bye folks  wierd stuff here...
AFL Dyfet  Perhaps we can move this discussion into the message base...
Andy Stein I'm afraid to use Bouncing Bluster and Tertosisas, because evry
           time, my
Andy Stein main directory gets messed up.
A2GS       LOL Andy
AFL Dyfet  Okay, I believe Scott has the next question...
AFL Scott  Has anyone seen problems with self-modifying code on a GS with a
           Transwarp?
A2GS       But only while your using that app. under that SYS. disk, right?
Coach101   No, but since they hav a cache, it certianly could be a problem!
AFL Scott  Reason I'm asking is that I'm working on a contract where the code
           is 
AFL Dyfet  Scott, the Cache may be killing you (as Coach just said)...
AFL Scott  heavily self-modifying and it appears to work on some TWGS's but
           not on 
AFL Scott  others.
AFA Parik  turn off interrupts before modifying?
AFL Dyfet  GA Dave...
AFL Scott  I'm aware of that, but one would think that the cache would see a
           miss and
AFL Scott  re-read.
Dave Lyons Before we jump off the deep end, isn't their cache write-through? 
           It's pre-fetching that would kill
Dave Lyons self-modifying code, and there's enough self-modifying code in the
           Apple II world that
Dave Lyons I don't see how it can be a problem (I mean, everything would
           break).  Including all OS calls
AFL Dyfet  Most self modifying code I have seen does have some distance
           between the
AFL Dyfet  instructions doing the modifying, and the modified
           instruction...
AFL Dyfet  Usually it's a jump address being co-erced further in, or some
           games with an
AFL Dyfet  absolute address being used as a pointer in a LDA/STA...
Coach101   Scott, you probably need to call AE and get some details on their
           cache implementation.
Coach101   And let us know what they say!
AFL Dyfet  Scott, also, are you modifying the NEXT instruction to be
           executed, or
AFL Dyfet  something further in the program that comes in later?
Coach101   I presume all the cards pass AE built-in diagnostics?
AFA Parik  (someone should also tell Zip Chip @ AppleFest just in case)
AFL Dyfet  Another tricky one may be branches...some cache systems try to
           follow both
AFL Dyfet  paths, just in case...
Coach101   And then there is DMA!
AFL Dyfet  We lost Scott...
AFL Dyfet  Well, without knowing the specific cercumstances, there isn't much
           to speculate
AFL Dyfet  on...A2 has the next question and the floor now...GA A2...
A2GS       Where can I get info on writing decompression routines for the 3
           (I believe)
A2GS       standard $C0 filetypes.
A2GS       ?
A2GS       GA
AFL Dyfet  GA Parik...
AFA Parik  source code is provided in the adv library.  i wrote a exe file
           that will unpac
AFA Parik  all three.  look for dev util #1 source code.  there are also
           others. ga
A2GS       Prefer text.
AFA Parik  (a filetype technote details the exact format if you wish)
A2GS       APW Shell file?
AFA Parik  apw/orca/merlin/prosel
A2GS       Thanx GA
AFL Dyfet  Okay, I believe that Dave Lyons has the next question...GA
           Dave...
Dave Lyons Oh, hi...wasn't paying
Dave Lyons attention. :)  Anyway, as I was saying
Dave Lyons before I got so rudely kicked off my connection ("Login failure:
           your account is already
Dave Lyons logged on."), uh,
A2GS       Dave, just plug it into the wall and turn on the button on the
           back.   :)
Dave Lyons there is self-modifying code
Dave Lyons in the APW C library routines that make GS/OS calls, so if the
           TWGS didn't deal with
Dave Lyons self-modifying code, I think we'd have noticed it already.  ga
Coach101   It may have to do with the spacing between the
Coach101   modification and the modifier and how recently
Coach101   the modified element was cached....
AFL Dyfet  Considering how many 'esoteric' coding practices have been used in
           the history
AFL Dyfet  of Apple II programming, I suspect you are correct, Dave :)...but
           it would have
AFL Dyfet  been helpful to know the exact circumstances he was working
           with...
Dave Lyons FYI, the self-
Dave Lyons mod code in the library is STA blah, JSL $E100A8, blah(word). 
           It's very near-by in
Dave Lyons memory, but then it isn't actually fetched for a while.  Hmmm.
AFL Dyfet  Dave, that's near, but not as near as    INC blah, LDA #blah, for
           example :)
Dave Lyons (What?   INC Blah+1,  Blah: LDA #blarg  ?)
AFL Dyfet  Yes...
Dave Lyons Well, I have no TWGS here at home...somebody try it.
A2GS       Why not just INC Blah ?
AFA Parik  will try, brb
Dave Lyons (Because INC Blah would make the LDA # into a TAX. :)
A2GS       Blah could be holding a number.
AFL Dyfet  That would also be self modifying, A2 :)...
AFL Dyfet  But it would be the LDA that is modified :)
A2GS       Just the fact that the number at blah is incremented...means that
           blah is being
A2GS       modified.
A2GS       blah doesn't have to be an op-code.
Dave Lyons Oh, I see what you're saying...I guess the idea
Dave Lyons is that if there's a problem with self-mod code, it's because of
           the processor (or its close
Dave Lyons friends) fetching *instructions* ahead, but always doing a real
           memory or cache access for data,
Dave Lyons since it *expects* that data changes.  Yes?
AFL Dyfet  Yes, basically, Dave...I've seen MUCH WORSE problems on heavily
           cached RISC
AFL Dyfet  machines, for example :)
A2GS       couldn't be, otherwise there would be a potential problem with any
           INC op.
AFL Dyfet  Well, now that Scott is back, we may find out just what he was
           modifying :)
AFL Scott  Dave, I was wondering if you could explain your use of
           Pre-Fetched.
AFL Scott  (I'm sorry, I was bumped and the system wouldn't let me sign back
           on until
AFL Scott  the darn in use flag was cleared).
AFA Parik  (it blew my motherboard!  :)  just kidding, worked fine)
Dave Lyons (Me, right?)
AFL Scott  Right, Dave Lyons.
Dave Lyons What I was saying is that a write-through cache, like I believe
           the TWGS has,
Dave Lyons doesn't present a problem, because all stores go
Dave Lyons to real memory & maybe also to the cache, but they never leave
           outdated information in the
Dave Lyons cache.  Pre-fetching, or pipelining (if I'm using the term
           correctly) would be some
Dave Lyons additional storage where upcoming instructions are stored, but
           which *isn't* updated on writes.  THAT
Dave Lyons would be a problem, but as far as I know the TWGS does NOT
           implement anything like that.  (I
Dave Lyons hypothesize that if it *did*, life would be very bad for a lot of
           existing Apple II software.  But
Dave Lyons I could be wrong.)
Dave Lyons ga
AFL Dyfet  While performing the write to real memory (for the write-through),
           the TW may
AFL Dyfet  still acknowledge CPU requests from memory pre-fetched, HOWEVER,
           it may not
AFL Dyfet  immediately update the cache memory as well, since that would
           waste an extra
AFL Dyfet  (7mhz) cycle...this is typical in many RISC caching systems...
Dave Lyons Can you suggest a test that would resolve the question?
Matt DTS   I think I'm gonna take off.  G'night, all.
AFL Scott  Thanks, Dave and David.  A test.. yeah.
AFL Dyfet  Try the inc BLAH, blah: lda #0, and see if a TAX was executed
           before a brk :)
AFL Scott  And I've done it... it works on my machine but has problems on
           others.
AFL Dyfet  (in other words, LDX #0, LDA #1, INC BLAH  blah: LDA #0, 
           BRK...:)
AFL Scott  See, I have a problem with self modifying code in terms of
           reliability and
AFL Scott  maintainability in APPLICATIONS.
A2GS       Are we still on blah?
AFL Dyfet  (wwops, make that LDA #0, LDX #1 :)
Dave Lyons Scott, on the machines where it
Dave Lyons malfunctions, does disabling the TWGS solve the problem?
AFL Scott  Yes and no... The problems seem to stem from timing.  So, when the
           machine is
AFL Scott  in Slow, it works.  This isn't acceptable to me... Additional
           problems surface
AFL Scott  when Sane calls are caught by the FPE init ( I haven't seen those
           either).
Dave Lyons Is any of your code getting executed at interrupt time?
AFL Scott  For the record, it's not MY code.... Explain interrupt time.
Dave Lyons Well, interrupt time is when an interrupt has come along (a
           heartbeat
Dave Lyons interrupt, sound interrupt, or whatever), but has not yet returned
           control to the code it
Dave Lyons interrupted.  Self-mod code is very scary if you've got any of the
           same code running in the foreground
Dave Lyons *and* getting called from inside an interrupt...it's very hard to
           be reentrant
Dave Lyons that way.
A2GS       In other words, are any interrupt handling routines vectored
           toward your code?
A2GS       I believe that's what DAVE is asking, right?
AFL Scott  No, there are no interrupt routines in the code I'm working with. 
           Only thing
AFL Scott  that happens is a DMA comes along from a hardware device but that
           is way after
AFL Scott  this code is called.
Dave Lyons Yes, Thank you, Paul, you've crystalized my thoughts exactly.
Dave Lyons :)
A2GS       Paul??
A2GS       :)
Dave Lyons (That's what Letterman sez to Paul all the time)
A2GS       Remind me to listen to Sheaffers return comment  :)
AFL Scott  IE... there is no interrupting going on...  The DMA call is
           initiated with
AFL Scott  a JSL to the ROM on the Board.
AFL Scott  And I don't see that, either.. but that's what they do... 
Dave Lyons Well Scott, something *weird* is going on in them thar
           machines...hard to tell what it is from
Dave Lyons here.  You've *never* seen a problem w/o a TWGS in there,
           though?
A2GS       What do you expect...it's an Apple  :)
AFL Scott  Never.  In fact the company I
AFL Scott  am doing this for is recommending pulling the TWGS, and I find
           that 
AFL Scott  an unacceptable compromised.
AFL Scott  -d.
AFL Scott  I shouldn't have asked this here, though.  I should ask AE.
AFL Scott  Rather I shouldn't have gone this deep.