"Which HDD Do I Have?" HDD Modes Explained

On PlayStation 2, saying "I have an HDD" can describe four fundamentally different hardware architectures and filesystem setups. launcHER needs to know how Ember is accessed, not just what physical drive is plugged in.

The Fundamental Rule

launcHER does NOT require a dedicated HDD partition.
You do not need to format your drive with APA or create __.EMBER if you already have Ember working on exFAT or USB. Choose the configuration that points directly to where Ember currently lives.

The Decision Tree

Ask yourself these two simple questions to identify your mode:

1. Is the drive plugged into USB?

If your HDD or SSD is connected through an external USB port, it is USB Mass Storage. Use mass?:/EMBER/ember.elf.

2. Is it in the console Expansion Bay?

If your drive is mounted inside the fat PS2 Network Adapter expansion bay, check whether it is formatted as exFAT (ATA BDM) or APA / PFS partitions.

WHERE IS EMBER STORED?

├── USB External Drive (HDD / SSD / Flash Drive)
│   └── path=mass?:/EMBER/ember.elf
│
├── Internal Expansion Bay HDD — Pure exFAT
│   └── path=ata:/EMBER/ember.elf
│       arg=-dev9=NICHDD
│
├── Internal Expansion Bay HDD — Mixed APA-Jail
│   ├── If Ember is on the exFAT side:
│   │   └── path=ata:/EMBER/ember.elf
│   │       arg=-dev9=NICHDD
│   │
│   └── If Ember is inside an APA partition:
│       └── path=hdd0:<PARTITION>:pfs:/EMBER/ember.elf
│           arg=pfs0:/EMBER/ember.elf
│           arg=-skip_argv0
│           arg=-dev9=NICHDD
│
└── Traditional Internal APA / PFS HDD
    └── path=hdd0:<PARTITION>:pfs:/EMBER/ember.elf
        arg=pfs0:/EMBER/ember.elf
        arg=-skip_argv0
        arg=-dev9=NICHDD

Mode 1: USB HDD / USB SSD

A spinning mechanical hard disk drive or 2.5" SSD plugged into a USB port (or USB hub) operates via the PS2's USB mass storage stack (usbd_mini.irx / bdm.irx).

Filesystem: FAT32 or exFAT.
Path format: mass?:/EMBER/ember.elf or usb?:/EMBER/ember.elf.
DEV9 needed? No. DEV9 is the internal network/HDD expansion interface and is not involved in USB.

# USB Profile in launcHER.CNF
path=mass?:/EMBER/ember.elf
arg=Soul Blade

Mode 2: Internal exFAT HDD (ATA BDM)

Modern PS2 setups often format the entire internal HDD with standard exFAT (single partition MBR/GPT). Games are stored as ordinary ISOs or folders under CD/, DVD/, and EMBER/.

Filesystem: Native exFAT accessed via the BDM ATA driver (ps2dev9.irx + ata_bd.irx).
Path format: ata:/EMBER/ember.elf.
DEV9 needed? YES (-dev9=NICHDD). launcHER must keep the network adapter and ATA controller powered so Ember can read from ata:/ after launcHER exits.
APA partition required? NO. There are no APA headers or PFS filesystems involved.

# Internal exFAT Profile in launcHER.CNF
path=ata:/EMBER/ember.elf
arg=Soul Blade
arg=-dev9=NICHDD

Mode 3: APA-Jail (Mixed APA + exFAT)

APA-Jail partitions an internal HDD with legacy APA headers at the start of the drive (for FMCB/FHDB or OSDMBR compatibility), followed by an unmanaged space formatted with standard exFAT.

Your path depends strictly on which section stores Ember:

If EMBER/ is on the exFAT filesystem, use the Internal exFAT (ATA BDM) configuration: path=ata:/EMBER/ember.elf.
If EMBER/ is stored inside one of the APA partitions (such as __.EMBER or __common), use the APA/PFS configuration below.

Mode 4: Internal APA / PFS HDD

Traditional PlayStation 2 HDD formatting where the drive is divided into APA partitions (e.g. __common, __system, +OPL, __.EMBER) formatted with Sony's PFS (PlayStation File System).

Can I use an existing partition?

YES. You do not need a partition named __.EMBER. If you have space in __common or another partition, put EMBER/ there and point launcHER at:

path=hdd0:__common:pfs:/EMBER/ember.elf

APA/PFS requires two distinct paths:

Loader target: hdd0:<PARTITION>:pfs:/EMBER/ember.elf tells launcHER which partition to mount.
Ember handoff: arg=pfs0:/EMBER/ember.elf tells Ember where to find itself once mounted.

# APA/PFS Profile in launcHER.CNF
path=hdd0:__.EMBER:pfs:/EMBER/ember.elf
arg=pfs0:/EMBER/ember.elf
arg=Soul Blade
arg=-skip_argv0
arg=-dev9=NICHDD

Where launcHER Lives vs Where Ember Lives

They do not need to be on the same device!

For example, you can store `launcHER.elf` inside your OPL APPS folder (on an APA partition or USB) while Ember and all its games live on the internal exFAT HDD:

launcHER location:  +OPL/APPS/Soul Blade/Soul Blade.ELF
launcHER.CNF:       path=ata:/EMBER/ember.elf
                    arg=Soul Blade
                    arg=-dev9=NICHDD
Ember location:     ata:/EMBER/ember.elf

launcHER reads its local launcHER.CNF, initializes the ATA storage driver, mounts the target device, and launches Ember with zero friction.