Re: Using 20SC with //GS?

[dempson@actrix.gen.nz (David Empson)]

Marvin Miller <marvinmiller@hotmail.com> wrote:

> Thank you very much for the comprehensive reply! As Greg mentioned in
> a later post, I am buying his 6 meg RAM card that he used successfully
> with his ROM 03 so I'm sure there won't be issues there as he used
> this combo for a while (from the sounds of it).

OK.  That is good to hear.  I'll see if I can coax some of my neurons
into retaining that detail in case the subject comes up again.

> After going through your post it seems that there are 'mass storage'
> difficulties with the //gs, at least in the hard drive department.
> This is unfortunate as I would have liked to have been able to store
> ALL Apple // programs currently available for d/l from the archives
> etc. (+/- 750 megs?) I thought that given modern storage capacity vs
> older, smaller progs - there would be no problems.

Unfortunately you are fighting an operating system which was designed in
1983, based on the assumption that you only needed two drives per slot
and seven slots!

> It seems that the number of partitions is the limiting factor here.
> Yuck! ;-)

Having larger partitions would help.  In theory, someone could write a
new 8-bit Apple II operating system that supports much larger
partitions, by using the SmartPort firmware interface on the Apple SCSI
cards (it isn't supported by the RamFast) instead of the ProDOS block
driver.

That isn't very likely, especially not while retaining application
compatibility with ProDOS.

> Anyway, one of the reasons why I ask all these questions is so that I
> can come up with a reasonable system design prior to purchasing the
> peripheral cards. To that end I've come up with my dream machine and
> it looks like this;
> 
> Rom 03 //GS (already bought)
> (2) 5.25 drives (already bought)
> (2) 3.5 drives (already bought)
> ZipGS card (already bought)
> 6 Meg AE card (already bought)
> 
> Now, I plan to add a ramKeeper as well (got a line on one right now
> and have to decide PDQ) and plug the 6 meg AE card into it and another
> identical 6 meg AE card as soon as I find one. This would give a total
> of 12 megs on the card + whatever's in the Rom 03 model. 

Does this actually work?  The IIgs memory expansion slot cannot
physically access more than 8 MB of RAM minus the motherboard "fast"
RAM, i.e. only 7 MB of RAM on an 8 MB card would be accessible in the
ROM 3.

Unless the RamKeeper does something special like set aside some of the
memory as a ROM disk, you won't be able to access all of the memory.

> AE also made a 2 meg daughtercard for each of the 6 meg cards which
> would bring the total installed memory to 16 megs if I could find
> them. This is, as I understand it, the most you can put in the //GS.

Nope.  The IIgs CPU has a 16 MB address space, but that doesn't mean all
of it can be RAM.

The motherboard hardware subdivided the address space as follows:

Banks
$00-$0F    1 MB  Motherboard "fast" RAM (on the ROM 3)
$10-$7F    7 MB  Memory expansion slot "fast" RAM
$80-$DF    6 MB  Unused
$E0-$E1  128 KB  Motherboard "slow" RAM
$E2-$EF  896 KB  Unused
$F0-$F7  512 KB  Memory expansion slot ROM (reserved for a ROM disk)
$F8-$FB  256 KB  Memory expansion slot ROM (reserved for firmware)
$FC-$FF  256 KB  Motherboard ROM (on the ROM 3)

(If you have a ROM 00 or 01, the "fast" RAM on the motherboard is only
128 KB, occupying banks $00 and $01, and the memory expansion slot
provides banks $02-$7F; the ROM is only banks $FE and $FF, with banks
$FC and $FD being added to the firmware expansion reserved area.)

The 6.875 MB of reserved address space is not decoded by the motherboard
hardware, and cannot be used by the memory expansion slot.  The only
case I'm aware of where these areas have been used is with a TransWarp
GS accelerator, which has some of its own code in ROM in the $Dx banks.
It can do this because it gets first crack at addresses provided by the
CPU, so it filters out these areas before passing all "normal" address
ranges on to the motherboard.

You can also use the banks above $7F in a IIgs emulator, since it
doesn't have to worry about hardware limitations.

> Storage is the next equation. The problems you have noted about
> partitions are new to me and very important. By your information I can
> see that by having both types of floppys active I can only use around
> 288 megs of the hard drive. Can I get around this limit by using 3 or
> 4 more hard drives using 288 on each?

No.  The limit on the number of partitions is the TOTAL number of
partitions on all accessible hard drives.

The RamFast SCSI card allows some flexing of this limit, because it has
a menu-driven program that lets you select which hard drive partitions
are currently mounted.  With the Apple SCSI cards, you get all the
ProDOS partitions it can find, in order, starting with the hard drive
with the highest SCSI ID, until it runs out of ProDOS unit numbers (the
9, 11 or 13 limit I mentioned).

Another possible solution is to use several hard drives but leave some
of them switched off, so you can select which partitions are currently
visible according to the drive(s) which are switched on.  This isn't
recommended - it can cause SCSI communication problems, particularly if
termination and/or termination power issues rear their ugly head.

> So I guess the questions I have left (at the moment) are architectural
> and experience related;
> 
> [1] Do you see anything wrong with the memory goals mentioned above?

See above.  I don't think it will work.

> [2] Can you run old A2 apps from the GS/OS (similar to a DOS window)?

You can run ProDOS applications directly from GS/OS.  It does this by
launching ProDOS-8, and once you're there, you are hit by the same
limits you would get by booting ProDOS-8 directly.

Neither ProDOS-8 nor GS/OS is able to run DOS 3.3 programs directly.
There is a program that lets you set up a disk image of a DOS 3.3 disk
on a hard drive and "boot" it, but this doesn't work with all programs.

> If so, than at least I can have the maximum number of partitions
> available to GS/OS?

You can only see all of the partitions available to GS/OS if you are
running native GS/OS applications.

> [3] Is Apple's SCSI implementation the same as conventional SCSI? IE:
> 8/16 devices, Drive ID's etc

The Apple II SCSI implementation is 8-bit (narrow) only, hence you are
limited to 7 drives per SCSI card (8 for the RamFast, since it doesn't
have a SCSI ID itself).

As far as the hardware goes, using most SCSI card in an Apple II gives
you a SCSI implementation which is almost identical to that of older
Macintosh models, except that it is a lot slower, and there are a few
termination issues to be aware of.  All Apple II SCSI cards use the
DB-25 connector (same as the built-in SCSI connector on older Mac
models).

Apple's own SCSI cards provide the most Mac-like and standard SCSI
implementation.  The RamFast supports a wider range of device types, but
doesn't fully implement the SCSI standard, and loses compatibility with
recent hard drives (due to the RamFast's lack of a SCSI ID and resulting
lack of support for the SCSI arbitration phase).

There are other third-party cards, such as the CMS SCSI card, but they
tend to have rather oddball implementations.  The CMS card uses jumper
settings to set the partition sizes on the hard drive.

I think there are a couple of other even more obscure brands, but I've
never encountered any others.


As far as speed goes:

- The original Apple SCSI card peaks at around 80 KB/sec.  It might do
  slightly better than this for large transfers under GS/OS.

- The Apple High-Speed SCSI card with DMA enabled typically achieves
  about 200 KB/sec on a IIgs with native software, somewhat less with
  ProDOS-8 (but still a lot better than the original Apple card).  When
  doing large consecutive transfers, it can get around 500 KB/sec under
  GS/OS, and with specially written software it can almost reach 1
  MB/sec.

- The RamFast has an onboard cache, so it typically runs much faster
  than the Apple High-speed SCSI card under ProDOS-8, but doesn't have
  as much of a speed advantage under GS/OS.  I haven't done any
  benchmarks, but I'd guess it would typically achieve 300 KB/sec
  under GS/OS, and about 500 KB/sec for large transfers.

> [4] Have you ever used a Zip drive on one of these puppies? I wonder
> if that might be useful.

I have connected my Zip drive on one occasion, and it worked.  You can
conveniently fit exactly three 32 MB ProDOS partitions on a Zip disk,
but Iomega's drivers on the Mac won't recognise such a disk.  You can
also use HFS (Mac) Zip disks under GS/OS, and I supposed you could use a
PC-formatted (FAT) disk with the MS-DOS FST or the third party MS-DOS
utilities (I haven't tried).

The Zip drive does not provide termination power, so you need another
device connected which can do this (I've always had a hard drive that
did this, so I've never modified any of my SCSI cards).

One thing to watch out for with the original Apple SCSI card: it is so
old that its firmware (even revision C) predates removable hard drives,
so if you are running ProDOS-8 and you have something like a Zip drive
or SyQuest, the SCSI card won't recognise when you eject a disk.  If the
next disk you insert doesn't have an identical partition table, then you
will corrupt the disk contents next time you write to it (the card's
firmware keeps using the old partition table).  You have to reboot to
safely change disks.

This problem doesn't affect the Apple High-Speed and RamFast cards.  It
also doesn't affect the original Apple card while you are in GS/OS,
because the GS/OS drivers are being used, not the firmware on the card.

> Oh, and a question to all, how do you guys run your storage? Anyone
> out there have around 750 megs of progs? How do you do it?

I've been through four hard drives on my two IIgs systems:

1. Rodime 69 MB.  Three ProDOS partitions, if I remember right.

This drive is effectively dead - it suffered an accident while
formatting and now refuses to reformat, but works (rather sluggishly)
with its last partitioning scheme.

(This drive cost me about NZ$3200 in 1988.  I don't remember what the
exchange rate was at the time, but I'd guess it was about US$2000.
Ouch!)

2. SyQuest 44 MB (removable cartridge).  Two ProDOS partions (32 MB and
   12 MB, I think) per cartridge, with about three cartridges that I was
   actively using.

I found the SyQuest to be slightly unreliable - it got I/O errors on
occasion.

3. Quantum LPS 240 MB.  I don't remember how I had this one set up -
   probably about 8 ProDOS partitions.

This drive worked beautifully.  I just ran out of space.  It is now
awaiting installation in a Mac SE/30 when I get around to it.

4. Quantum TrailBlazer 850 MB.  Ten 32 MB ProDOS partitions plus four
   128 MB HFS partitions.

This is the current (and final) drive.

I haven't used the machine for a while, but if memory serves, the
partitions on the last drive are divided as follows:

System and major applications, including most of the ProDOS-8 ones.
Development - source code, development tools, etc.
Data
PC Transporter (two 16 MB files making up a 32 MB hard drive image)
Reference material (technical notes, etc.)
GNO/ME
The remaining four ProDOS partitions are random combinations of E-Mail
and News archives, downloaded files in various states of disarray and
are generally a big mess.  The HFS partitions are similarly messy.

There is another small ProDOS partition (about 5 MB) in the remaining
space, on which I created a unified System 6.0.1 installer (all five
disks merged into one, with modified Installer scripts and the "Easy
Install" option disabled).  This partition is write protected, and it
has been quite handy on occasion.

I don't think I have many games on the hard drive - most of them are
still on floppies, and I'd expect that many of the 5.25" ones are
unreadable by now.