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27.Dd February 15, 2017
28.Dt AHC 4
29.Os
30.Sh NAME
31.Nm ahc
32.Nd Adaptec VL/ISA/PCI SCSI host adapter driver
33.Sh SYNOPSIS
34To compile this driver into the kernel,
35place the following lines in your
36kernel configuration file:
37.Bd -ragged -offset indent
38.Cd "device scbus"
39.Cd "device ahc"
40.Pp
41For one or more PCI cards:
42.Cd "device pci"
43.Pp
44To allow PCI adapters to use memory mapped I/O if enabled:
45.Cd options AHC_ALLOW_MEMIO
46.Pp
47To configure one or more controllers to assume the target role:
48.Cd options AHC_TMODE_ENABLE <bitmask of units>
49.Ed
50.Pp
51Alternatively, to load the driver as a
52module at boot time, place the following lines in
53.Xr loader.conf 5 :
54.Bd -literal -offset indent
55ahc_load="YES"
56ahc_isa_load="YES"
57ahc_pci_load="YES"
58.Ed
59.Sh DESCRIPTION
60This driver provides access to the
61.Tn SCSI
62bus(es) connected to the Adaptec AIC77xx and AIC78xx
63host adapter chips.
64.Pp
65Driver features include support for twin and wide busses,
66fast, ultra or ultra2 synchronous transfers depending on controller type,
67tagged queueing, SCB paging, and target mode.
68.Pp
69Memory mapped I/O can be enabled for PCI devices with the
70.Dq Dv AHC_ALLOW_MEMIO
71configuration option.
72Memory mapped I/O is more efficient than the alternative, programmed I/O.
73Most PCI BIOSes will map devices so that either technique for communicating
74with the card is available.
75In some cases,
76usually when the PCI device is sitting behind a PCI->PCI bridge,
77the BIOS may fail to properly initialize the chip for memory mapped I/O.
78The typical symptom of this problem is a system hang if memory mapped I/O
79is attempted.
80Most modern motherboards perform the initialization correctly and work fine
81with this option enabled.
82.Pp
83Individual controllers may be configured to operate in the target role
84through the
85.Dq Dv AHC_TMODE_ENABLE
86configuration option.
87The value assigned to this option should be a bitmap
88of all units where target mode is desired.
89For example, a value of 0x25, would enable target mode on units 0, 2, and 5.
90A value of 0x8a enables it for units 1, 3, and 7.
91.Pp
92Per target configuration performed in the
93.Tn SCSI-Select
94menu, accessible at boot
95is honored by this driver.
96This includes synchronous/asynchronous transfers,
97maximum synchronous negotiation rate,
98wide transfers,
99disconnection,
100the host adapter's SCSI ID.
101For systems that store non-volatile settings in a system specific manner
102rather than a serial eeprom directly connected to the aic7xxx controller,
103the
104.Tn BIOS
105must be enabled for the driver to access this information.
106This restriction applies to
107many chip-down motherboard configurations.
108.Pp
109Performance and feature sets vary throughout the aic7xxx product line.
110The following table provides a comparison of the different chips supported
111by the
112.Nm
113driver.
114Note that wide and twin channel features, although always supported
115by a particular chip, may be disabled in a particular motherboard or card
116design.
117.Bd -ragged -offset indent
118.Bl -column "aic7895CX" "MIPSX" "PCI/64X" "MaxSyncX" "MaxWidthX" "SCBsX" "2 3 4 5 6 7 8X"
119.It Em "Chip" Ta "MIPS" Ta "Bus" Ta "MaxSync" Ta "MaxWidth" Ta "SCBs" Ta "Features"
120.It "aic7770" Ta "10" Ta "VL" Ta "10MHz" Ta "16Bit" Ta "4" Ta "1"
121.It "aic7850" Ta "10" Ta "PCI/32" Ta "10MHz" Ta "8Bit" Ta "3" Ta ""
122.It "aic7860" Ta "10" Ta "PCI/32" Ta "20MHz" Ta "8Bit" Ta "3" Ta ""
123.It "aic7870" Ta "10" Ta "PCI/32" Ta "10MHz" Ta "16Bit" Ta "16" Ta ""
124.It "aic7880" Ta "10" Ta "PCI/32" Ta "20MHz" Ta "16Bit" Ta "16" Ta ""
125.It "aic7890" Ta "20" Ta "PCI/32" Ta "40MHz" Ta "16Bit" Ta "16" Ta "3 4 5 6 7 8"
126.It "aic7891" Ta "20" Ta "PCI/64" Ta "40MHz" Ta "16Bit" Ta "16" Ta "3 4 5 6 7 8"
127.It "aic7892" Ta "20" Ta "PCI/64" Ta "80MHz" Ta "16Bit" Ta "16" Ta "3 4 5 6 7 8"
128.It "aic7895" Ta "15" Ta "PCI/32" Ta "20MHz" Ta "16Bit" Ta "16" Ta "2 3 4 5"
129.It "aic7895C" Ta "15" Ta "PCI/32" Ta "20MHz" Ta "16Bit" Ta "16" Ta "2 3 4 5 8"
130.It "aic7896" Ta "20" Ta "PCI/32" Ta "40MHz" Ta "16Bit" Ta "16" Ta "2 3 4 5 6 7 8"
131.It "aic7897" Ta "20" Ta "PCI/64" Ta "40MHz" Ta "16Bit" Ta "16" Ta "2 3 4 5 6 7 8"
132.It "aic7899" Ta "20" Ta "PCI/64" Ta "80MHz" Ta "16Bit" Ta "16" Ta "2 3 4 5 6 7 8"
133.El
134.Pp
135.Bl -enum -compact
136.It
137Multiplexed Twin Channel Device - One controller servicing two busses.
138.It
139Multi-function Twin Channel Device - Two controllers on one chip.
140.It
141Command Channel Secondary DMA Engine - Allows scatter gather list and
142SCB prefetch.
143.It
14464 Byte SCB Support - SCSI CDB is embedded in the SCB to eliminate an extra DMA.
145.It
146Block Move Instruction Support - Doubles the speed of certain sequencer
147operations.
148.It
149.Sq Bayonet
150style Scatter Gather Engine - Improves S/G prefetch performance.
151.It
152Queuing Registers - Allows queueing of new transactions without pausing the
153sequencer.
154.It
155Multiple Target IDs - Allows the controller to respond to selection as a
156target on multiple SCSI IDs.
157.El
158.Ed
159.Sh HARDWARE
160The
161.Nm
162driver supports the following
163.Tn SCSI
164host adapter chips and
165.Tn SCSI
166controller cards:
167.Pp
168.Bl -bullet -compact
169.It
170Adaptec
171.Tn AIC7770
172host adapter chip
173.It
174Adaptec
175.Tn AIC7850
176host adapter chip
177.It
178Adaptec
179.Tn AIC7860
180host adapter chip
181.It
182Adaptec
183.Tn AIC7870
184host adapter chip
185.It
186Adaptec
187.Tn AIC7880
188host adapter chip
189.It
190Adaptec
191.Tn AIC7890
192host adapter chip
193.It
194Adaptec
195.Tn AIC7891
196host adapter chip
197.It
198Adaptec
199.Tn AIC7892
200host adapter chip
201.It
202Adaptec
203.Tn AIC7895
204host adapter chip
205.It
206Adaptec
207.Tn AIC7896
208host adapter chip
209.It
210Adaptec
211.Tn AIC7897
212host adapter chip
213.It
214Adaptec
215.Tn AIC7899
216host adapter chip
217.It
218Adaptec
219.Tn 274X(W)
220.It
221Adaptec
222.Tn 274X(T)
223.It
224Adaptec
225.Tn 2910
226.It
227Adaptec
228.Tn 2915
229.It
230Adaptec
231.Tn 2920C
232.It
233Adaptec
234.Tn 2930C
235.It
236Adaptec
237.Tn 2930U2
238.It
239Adaptec
240.Tn 2940
241.It
242Adaptec
243.Tn 2940J
244.It
245Adaptec
246.Tn 2940N
247.It
248Adaptec
249.Tn 2940U
250.It
251Adaptec
252.Tn 2940AU
253.It
254Adaptec
255.Tn 2940UW
256.It
257Adaptec
258.Tn 2940UW Dual
259.It
260Adaptec
261.Tn 2940UW Pro
262.It
263Adaptec
264.Tn 2940U2W
265.It
266Adaptec
267.Tn 2940U2B
268.It
269Adaptec
270.Tn 2950U2W
271.It
272Adaptec
273.Tn 2950U2B
274.It
275Adaptec
276.Tn 19160B
277.It
278Adaptec
279.Tn 29160B
280.It
281Adaptec
282.Tn 29160N
283.It
284Adaptec
285.Tn 3940
286.It
287Adaptec
288.Tn 3940U
289.It
290Adaptec
291.Tn 3940AU
292.It
293Adaptec
294.Tn 3940UW
295.It
296Adaptec
297.Tn 3940AUW
298.It
299Adaptec
300.Tn 3940U2W
301.It
302Adaptec
303.Tn 3950U2
304.It
305Adaptec
306.Tn 3960
307.It
308Adaptec
309.Tn 39160
310.It
311Adaptec
312.Tn 3985
313.It
314Adaptec
315.Tn 4944UW
316.It
317Many motherboards with on-board
318.Tn SCSI
319support
320.El
321.Sh SCSI CONTROL BLOCKS (SCBs)
322Every transaction sent to a device on the SCSI bus is assigned a
323.Sq SCSI Control Block
324(SCB).
325The SCB contains all of the information required by the
326controller to process a transaction.
327The chip feature table lists
328the number of SCBs that can be stored in on-chip memory.
329All chips
330with model numbers greater than or equal to 7870 allow for the on chip
331SCB space to be augmented with external SRAM up to a maximum of 255 SCBs.
332Very few Adaptec controller configurations have external SRAM.
333.Pp
334If external SRAM is not available, SCBs are a limited resource.
335Using the SCBs in a straight forward manner would only allow the driver to
336handle as many concurrent transactions as there are physical SCBs.
337To fully utilize the SCSI bus and the devices on it,
338requires much more concurrency.
339The solution to this problem is
340.Em SCB Paging ,
341a concept similar to memory paging.
342SCB paging takes advantage of
343the fact that devices usually disconnect from the SCSI bus for long
344periods of time without talking to the controller.
345The SCBs for disconnected transactions are only of use to the controller
346when the transfer is resumed.
347When the host queues another transaction
348for the controller to execute, the controller firmware will use a
349free SCB if one is available.
350Otherwise, the state of the most recently
351disconnected (and therefore most likely to stay disconnected) SCB is
352saved, via dma, to host memory, and the local SCB reused to start
353the new transaction.
354This allows the controller to queue up to
355255 transactions regardless of the amount of SCB space.
356Since the
357local SCB space serves as a cache for disconnected transactions, the
358more SCB space available, the less host bus traffic consumed saving
359and restoring SCB data.
360.Sh SEE ALSO
361.Xr ahd 4 ,
362.Xr cd 4 ,
363.Xr da 4 ,
364.Xr sa 4 ,
365.Xr scsi 4
366.Sh HISTORY
367The
368.Nm
369driver appeared in
370.Fx 2.0 .
371.Sh AUTHORS
372The
373.Nm
374driver, the
375.Tn AIC7xxx
376sequencer-code assembler,
377and the firmware running on the aic7xxx chips was written by
378.An Justin T. Gibbs .
379.Sh BUGS
380Some Quantum drives (at least the Empire 2100 and 1080s) will not run on an
381.Tn AIC7870
382Rev B in synchronous mode at 10MHz.
383Controllers with this problem have a
38442 MHz clock crystal on them and run slightly above 10MHz.
385This confuses the drive and hangs the bus.
386Setting a maximum synchronous negotiation rate of 8MHz in the
387.Tn SCSI-Select
388utility will allow normal operation.
389.Pp
390Although the Ultra2 and Ultra160 products have sufficient instruction
391ram space to support both the initiator and target roles concurrently,
392this configuration is disabled in favor of allowing the target role
393to respond on multiple target ids.
394A method for configuring dual role mode should be provided.
395.Pp
396Tagged Queuing is not supported in target mode.
397.Pp
398Reselection in target mode fails to function correctly on all high
399voltage differential boards as shipped by Adaptec.
400Information on
401how to modify HVD board to work correctly in target mode is available
402from Adaptec.
403