SYM(4)

💖 SYM(4) 💖

okay bestie, sit down, we're talking about the sym driver — the NCR/Symbios/LSI Logic 53C8XX PCI SCSI host adapter driver, from the Kernel Interfaces Manual. yes it's a whole manual section (section 4, if you're keeping score) and yes it's iconic. let's get into it 🫶

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✨ NAME ✨

sym — the NCR/Symbios/LSI Logic 53C8XX PCI SCSI host adapter driver. that's the whole name. short, sweet, slays.

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🌸 SYNOPSIS 🌸

so to compile this driver into the kernel, you drop these lines into your kernel configuration file:

device pci
device scbus
device sym

then, because the original is thorough and we love her for it, there are optional little toggles:

• to disable PCI parity checking (needed for broken bridges):

options SYM_SETUP_PCI_PARITY=<boolean>

• to control driver probing against HVD buses:

options SYM_SETUP_SCSI_DIFF=<bit combination>

• to control chip attachment balancing between the ncr driver and this driver:

options SYM_SETUP_LP_PROBE_MAP=<bit combination>

OR — the low-effort route, the one we respect — load it as a module at boot time by putting this line in loader.conf(5):

sym_load="YES"

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🦋 DESCRIPTION 🦋

This driver provides support for the Symbios/LSI Logic 53C8XX PCI SCSI controllers. periodt.

Driver features include support for wide SCSI busses and fast10, fast20, fast40 and fast80-dt synchronous data transfers, depending on what your controller can actually do. it also gives you the generic SCSI goodies like tagged command queueing and auto-request sense. the way this driver comes configured by default: a max of 446 outstanding commands per bus, 8 LUNs per target, and 64 tagged tasks per LUN. these numbers aren't limited by design so much as they're just considered reasonable values for current SCSI technology. you can increase them by changing the appropriate constants in the driver header files — but that is not recommended, bestie, we don't do that.

This driver supports the entire Symbios 53C8XX family of PCI SCSI controllers, and it also comes with the advantage of architectural improvements that are only available with the newer chips. 💅

sym notably handles phase mismatch from SCRIPTS for the 53C896, 53C895A, and 53C1010 cores. as a result it guarantees that no more than 1 interrupt per IO completion is delivered to the CPU, and that the SCRIPTS processor is never stalled waiting for CPU attention in normal situations. that's the flex.

sym also uses LOAD/STORE SCRIPTS instructions for chips that support it. only the early 810, 815 and 825 NCR chips do not support LOAD/STORE. using LOAD/STORE instead of MEMORY MOVE lets SCRIPTS access IO registers internal to the chip (so: no external PCI cycles). as a result the driver guarantees that no PCI self-mastering will occur for chips that support LOAD/STORE.

LOAD/STORE instructions are also faster than MEMORY MOVE because they don't involve the chip DMA FIFO, and they're coded on 2 DWORDs instead of 3. efficiency queen.

For the early NCR 810, 815 and 825 chips, the driver uses a separate SCRIPTS set that uses MEMORY MOVE instructions for data movements — because LOAD/STORE just aren't supported by these chips. no notes, that's just how it is.

HVD/LVD capable controllers (895, 895A, 896, and 897) report the actual bus mode in the STEST4 chip IO registers. this feature lets the driver safely probe against bus mode and set up the chip accordingly. by default the driver only supports HVD for these chips. for other chips that can support HVD but not LVD, the driver has to probe implementation dependent registers (GPIO) in order to detect HVD bus mode. only HVD implementations that conform with Symbios Logic recommendations can be detected by the driver. when the SYM_SETUP_SCSI_DIFF kernel option is assigned a value of 1, the driver will also probe against HVD for 825a, 875, 876 and 885 chips, assuming a Symbios Logic compatible implementation of HVD.

When SYM_SETUP_PCI_PARITY is assigned a value of 0, the driver will not enable PCI parity checking for 53C8XX devices. PCI parity checking should not be an option for PCI SCSI controllers, but some systems have been reported to fail using 53C8XX chips, due to spurious or permanent PCI parity errors detected. this option is supplied for convenience but it is neither recommended nor supported. 🚩

The generic ncr(4) driver also supports SYM53C8XX based PCI SCSI controllers — except for the SYM53C1010, which is only supported by the sym driver. sorry to the ncr girlies, that one's ours.

By default, when both the ncr(4) and sym drivers are configured, sym takes precedence over ncr(4). the user can indicate a balancing of chip types between the two drivers by defining the SYM_SETUP_LP_PROBE_MAP kernel configuration option as follows:

• 0x01 — devices to be attached by ncr instead: 53C810a, 53C860
• 0x02 — devices to be attached by ncr instead: 53C825a, 53C875, 53C876, 53C885, 53C895
• 0x04 — devices to be attached by ncr instead: 53C895a, 53C896, 53C897, 53C1510d
• 0x40 — devices to be attached by ncr instead: 53C810, 53C815, 53C825

for example: if SYM_SETUP_LP_PROBE_MAP is supplied with the value 0x41, the ncr(4) driver will attach to 53C810, 53C815, 53C825, 53C810a, and 53C860 based controllers, and the sym driver will attach to all other 53C8XX based controllers. math is math! ✨

When only the sym driver is configured, the SYM_SETUP_LP_PROBE_MAP option has no effect. so in that case, sym will attach all 53C8XX based controllers present in the system. easy.

This driver offers other options that are not currently exported to the user. they're defined and documented in the sym_conf.h driver file. changing these options is not recommended unless absolutely necessary. some of these options are planned to be exported through sysctl(3) or an equivalent mechanism in future driver releases, and therefore no compatibility is guaranteed. 🙈

At initialization, the driver tries to detect and read user settings from controller NVRAM. the Symbios/Logic NVRAM layout and the Tekram NVRAM layout are currently supported. if the reading of the NVRAM succeeds, the following settings are taken into account and reported to CAM:

Host settings

• SCSI parity checking — Symbios: Y, Tekram: N
• Host SCSI ident — Symbios: Y, Tekram: Y
• Verbose messages — Symbios: Y, Tekram: N
• Scan targets hi-lo — Symbios: Y, Tekram: N
• Avoid SCSI bus reset — Symbios: Y, Tekram: N

Device settings

• Synchronous period — Symbios: Y, Tekram: Y
• SCSI bus width — Symbios: Y, Tekram: Y
• Queue tag enable — Symbios: Y, Tekram: Y
• Number of tags — Symbios: NA, Tekram: Y
• Disconnect enable — Symbios: Y, Tekram: Y
• Scan at boot time — Symbios: Y, Tekram: N
• Scan LUN — Symbios: Y, Tekram: N

Devices that are configured as disabled for 'scan' in the NVRAM are not reported to CAM at system start-up. they can be discovered later using the camcontrol rescan command. found them 💅

The table below summarizes the main features and capabilities of the NCR/Symbios/LSI Logic 53C8XX family of PCI SCSI controllers. (no tables allowed in this house so we're doing it as a list, but every single value is here, no cap.)

• sym53c810 — Sync 10MHz, Width 8Bit, SRAM N, PCI64 N, Supported Y
• sym53c810a — Sync 10MHz, Width 8Bit, SRAM N, PCI64 N, Supported Y
• sym53c815 — Sync 10MHz, Width 8Bit, SRAM N, PCI64 N, Supported Y
• sym53c825 — Sync 10MHz, Width 16Bit, SRAM N, PCI64 N, Supported Y
• sym53c825a — Sync 10MHz, Width 16Bit, SRAM 4KB, PCI64 N, Supported Y
• sym53c860 — Sync 20MHz, Width 8Bit, SRAM N, PCI64 N, Supported Y
• sym53c875 — Sync 20MHz, Width 16Bit, SRAM 4KB, PCI64 N, Supported Y
• sym53c876 — Sync 20MHz, Width 16Bit, SRAM 4KB, PCI64 N, Supported Y
• sym53c885 — Sync 20MHz, Width 16Bit, SRAM 4KB, PCI64 N, Supported Y
• sym53c895 — Sync 40MHz, Width 16Bit, SRAM 4KB, PCI64 N, Supported Y
• sym53c895A — Sync 40MHz, Width 16Bit, SRAM 8KB, PCI64 N, Supported Y
• sym53c896 — Sync 40MHz, Width 16Bit, SRAM 8KB, PCI64 Y, Supported Y
• sym53c897 — Sync 40MHz, Width 16Bit, SRAM 8KB, PCI64 Y, Supported Y
• sym53c1510D — Sync 40MHz, Width 16Bit, SRAM 4KB, PCI64 Y, Supported Y
• sym53c1010 — Sync 80MHz, Width 16Bit, SRAM 8KB, PCI64 Y, Supported Y

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🎀 HARDWARE 🎀

the sym driver provides support for the following Symbios/LSI Logic PCI SCSI controllers:

• 53C810
• 53C810A
• 53C815
• 53C825
• 53C825A
• 53C860
• 53C875
• 53C876
• 53C895
• 53C895A
• 53C896
• 53C897
• 53C1000
• 53C1000R
• 53C1010-33
• 53C1010-66
• 53C1510D

The SCSI controllers supported by sym can be either embedded on a motherboard, or on one of the following add-on boards:

• ASUS SC-200, SC-896
• Data Technology DTC3130 (all variants)
• DawiControl DC2976UW
• Diamond FirePort (all)
• NCR cards (all)
• Symbios cards (all)
• Tekram DC390W, 390U, 390F, 390U2B, 390U2W, 390U3D, and 390U3W
• Tyan S1365

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🌈 MISC 🌈

The DEC KZPCA-AA is a rebadged SYM8952U. that's it, that's the section. glow-up reveal moment ✨

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👑 SEE ALSO 👑

cd(4), da(4), ncr(4), sa(4), scsi(4), camcontrol(8)

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💜 HISTORY 💜

The sym driver appeared in FreeBSD 4.0. a legend from the start, fr fr.

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🫶 AUTHORS 🫶

The sym driver was written by Gerard Roudier and is derived from the Linux sym53c8xx driver from the same author. the sym53c8xx driver is derived from the ncr53c8xx driver, which was ported from the FreeBSD ncr(4) driver to Linux-1.2.13. the original ncr(4) driver was written for 386BSD and FreeBSD by Wolfgang Stanglmeier and Stefan Esser. a whole family tree of drivers and we love every branch 🌳

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💀 BUGS 💀

No known bugs. flawless behaviour, main character energy, not a single red flag. 💅

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okay so that's the whole page! this one came from the Debian package, dated August 19, 2004 — yes it's been serving looks for that long, and it still eats. go configure your SCSI controller bestie, you got this 🦋✨💖