HP OpenVMS Systems Documentation
OpenVMS Version 7.3 Release Notes
7.17 OpenVMS Alpha SCSI Firmware Support
The following sections relate to SCSI firmware support.
The minimum firmware revision level recommended for RZ26N and RZ28M disks is Revision 0568.
If the latest firmware revision level is not used with these disks,
multiple problems may occur.
If you install RZ26L or RZ28 disks on a multihost SCSI bus in an OpenVMS Cluster, the disk's minimum firmware revision is 442.
The following sections describe a procedure that can be used to update the firmware on some RZ26L and RZ28 drives. This procedure can only be used with drives that are directly connected to a SCSI adapter on a host system. Drives that are attached through an intelligent controller (such as an HSZ40 or KZPSC) cannot be updated using this procedure. Refer to the intelligent controller's documentation to determine whether an alternative firmware update procedure exists.
7.17.3 Firmware Revision Level 442 Requirements
Only the combinations of disk drives and firmware revision levels listed in Table 7-3 are capable of being upgraded safely to firmware revision level 442. Performing the update procedure on any other combination can permanently damage the disk.
7.17.4 Firmware Revision Level 442 Installation Procedure
If you determine that your disk requires revision level 442 firmware and it is capable of being upgraded safely, use the following procedure to update the firmware. (See Table 7-3 for the file name of the disk you are upgrading.)
7.18 OpenVMS Alpha SCSI Port and Class Drivers
The following sections describe OpenVMS Alpha SCSI class and port
device driver restrictions.
Version 6.2 and later of OpenVMS Alpha supports various add-on SCSI adapters. Compaq's AlphaGeneration platforms typically support one or more integral SCSI adapters, with the option of installing additional add-on SCSI adapters. Due to differences in device-naming conventions used between the Alpha console and OpenVMS, the OpenVMS device name may not match the name displayed by the console.
For example, the console designation for a SCSI device on the integral SCSI adapter may be DKA100. However, when two additional add-on SCSI adapters are added, the "A" designation becomes "C", and DKA100 appears as DKC100 when OpenVMS is running.
Note that although the console and OpenVMS device names may be
different, the unique specification of a device name from the console
to the device name under OpenVMS stays consistent, provided add-on SCSI
adapters are not added or removed.
As a result of the SCSI-2 Tagged Command Queuing (TCQ) support in OpenVMS Alpha Version 6.2, Compaq has determined that customers with KZMSA XMI to SCSI and Adaptec 1742A adapters may experience a 20% SCSI disk I/O performance degradation because TCQ is not implemented for these adapters. The performance degradation is in the area of increased CPU cost per I/O. Customers running at less than maximum CPU utilization under OpenVMS Alpha Version 6.1 may not experience any degradation under OpenVMS Alpha Version 6.2.
Compaq does not expect this situation to significantly affect DEC 7000 customers planning to upgrade to DEC 8000 Family systems using KZMSA adapters because the speed of those processors should offset the performance degradation. However, DEC 7000 customers who upgrade to OpenVMS Alpha Version 6.2 will experience the SCSI I/O disk performance degradation.
Compaq expects that this will significantly affect existing DEC 2000
Model 300 systems customers that use the Adaptec 1742A SCSI adapter.
As of OpenVMS Version 7.2, the Writing OpenVMS Alpha Device Drivers in C manual no longer ships
with the OpenVMS documentation set. The latest revision of this manual
is available from Digital
OpenVMS Alpha Version 7.3 has implemented stricter requirements for SCSI Mode Page 01h (the Read Write Error Recovery Page) for SCSI tape drives. These requirements help guard against possible data loss during write operations to SCSI tape, by defining the recovery actions to be taken in the event of deferred recoverable errors. For most Compaq-supported drives, these changes will not affect the drive's behavior. For some drives, however, these new requirements may impact SCSI tape behavior in the following two ways:
To run the SRM_CHECK tool, define it as a foreign command (or use the DCL$PATH mechanism) and invoke it with the name of the image to check. If a problem is found, the machine code is displayed and some image information is printed. The following example illustrates how to use the tool to analyze an image called myimage.exe:
$ define DCL$PATH  $ srm_check myimage.exe
The tool supports wildcard searches. Use the following command line to initiate a wildcard search:
$ srm_check [*...]* -log
Use the -log qualifier to generate a list of images that have been checked. You can use the -output qualifier to write the output to a data file. For example, the following command directs output to a file named CHECK.DAT:
$ srm_check 'file' -output check.dat
You can use the output from the tool to find the module that generated the sequence by looking in the image's MAP file. The addresses shown correspond directly to the addresses that can be found in the MAP file.
The following example illustrates the output from using the analysis tool on an image named SYSTEM_SYNCHRONIZATION.EXE:
** Potential Alpha Architecture Violation(s) found in file... ** Found an unexpected ldq at 00003618 0000360C AD970130 ldq_l R12, 0x130(R23) 00003610 4596000A and R12, R22, R10 00003614 F5400006 bne R10, 00003630 00003618 A54B0000 ldq R10, (R11) Image Name: SYSTEM_SYNCHRONIZATION Image Ident: X-3 Link Time: 5-NOV-1998 22:55:58.10 Build Ident: X6P7-SSB-0000 Header Size: 584 Image Section: 0, vbn: 3, va: 0x0, flags: RESIDENT EXE (0x880)
The MAP file for system_synchronization.exe contains the following:
EXEC$NONPAGED_CODE 00000000 0000B317 0000B318 ( 45848.) 2 ** 5 SMPROUT 00000000 000047BB 000047BC ( 18364.) 2 ** 5 SMPINITIAL 000047C0 000061E7 00001A28 ( 6696.) 2 ** 5
The address 360C is in the SMPROUT module, which contains the addresses from 0-47BB. By looking at the machine code output from the module, you can locate the code and use the listing line number to identify the corresponding source code. If SMPROUT had a nonzero base, you would need to subtract the base from the address (360C in this case) to find the relative address in the listing file.
Note that the tool reports potential violations in its output.
Although SRM_CHECK can normally identify a code section in an image by
the section's attributes, it is possible for OpenVMS images to contain
data sections with those same attributes. As a result, SRM_CHECK may
scan data as if it were code, and occasionally, a block of data may
look like a noncompliant code sequence. This circumstance is rare and
can be detected by examining the MAP and listing files.
8.3 Characteristics of Noncompliant Code
The areas of noncompliance detected by the SRM_CHECK tool can be grouped into the following four categories. Most of these can be fixed by recompiling with new compilers. In rare cases, the source code may need to be modified. See Section 8.5 for information about compiler versions.
If the SRM_CHECK tool finds a violation in an image, you should
recompile the image with the appropriate compiler (see Section 8.5).
After recompiling, you should analyze the image again. If violations
remain after recompiling, examine the source code to determine why the
code scheduling violation exists. Then make the appropriate changes to
the source code.
8.4 Coding Requirements
The Alpha Architecture Reference Manual describes how an atomic update of data between processors must be formed. The Third Edition, in particular, has much more information on this topic. This edition details the conventions of the interlocked memory sequence.
Exceptions to the following two requirements are the source of all known noncompliant code:
LDx_L Rx, n(Ry) ... label: ... STx_C Rx, n(Ry)
Therefore, the SRM_CHECK tool looks for the following:
To illustrate, the following are examples of code flagged by SRM_CHECK.
** Found an unexpected ldq at 0008291C 00082914 AC300000 ldq_l R1, (R16) 00082918 2284FFEC lda R20, 0xFFEC(R4) 0008291C A6A20038 ldq R21, 0x38(R2)
In the above example, an LDQ instruction was found after an LDQ_L before the matching STQ_C. The LDQ must be moved out of the sequence, either by recompiling or by source code changes. (See Section 8.3.)
** Backward branch from 000405B0 to a STx_C sequence at 0004059C 00040598 C3E00003 br R31, 000405A8 0004059C 47F20400 bis R31, R18, R0 000405A0 B8100000 stl_c R0, (R16) 000405A4 F4000003 bne R0, 000405B4 000405A8 A8300000 ldl_l R1, (R16) 000405AC 40310DA0 cmple R1, R17, R0 000405B0 F41FFFFA bne R0, 0004059C
In the above example, a branch was discovered between the LDL_L and STQ_C. In this case, there is no "fall through" path between the LDx_L and STx_C, which the architecture requires.
This branch backward from the LDx_L to the STx_C is characteristic of the noncompliant code introduced by the "loop rotation" optimization.
The following MACRO--32 source code demonstrates code where there is a "fall through" path, but this case is still noncompliant because of the potential branch and a memory reference in the lock sequence.
getlck: evax_ldql r0, lockdata(r8) ; Get the lock data movl index, r2 ; and the current index. tstl r0 ; If the lock is zero, beql is_clear ; skip ahead to store. movl r3, r2 ; Else, set special index. is_clear: incl r0 ; Increment lock count evax_stqc r0, lockdata(r8) ; and store it. tstl r0 ; Did store succeed? beql getlck ; Retry if not.
To correct this code, the memory access to read the value of INDEX must first be moved outside the LDQ_L/STQ_C sequence. Next, the branch between the LDQ_L and STQ_C, to the label IS_CLEAR, must be eliminated. In this case, it could be done using a CMOVEQ instruction. The CMOVxx instructions are frequently useful for eliminating branches around simple value moves. The following example shows the corrected code:
movl index, r2 ; Get the current index getlck: evax_ldql r0, lockdata(r8) ; and then the lock data. evax_cmoveq r0, r3, r2 ; If zero, use special index. incl r0 ; Increment lock count evax_stqc r0, lockdata(r8) ; and store it. tstl r0 ; Did write succeed? beql getlck ; Retry if not.
This section contains information about versions of compilers that may generate noncompliant code sequences and the recommended versions to use when recompiling.
Table 8-1 contains information for OpenVMS compilers.
|Old Version||Recommended Minimum Version|
|BLISS V1.1||BLISS V1.3|
|DEC Ada V3.5||Compaq Ada V3.5A|
|DEC C V5.x||DEC C V6.0|
|DEC C++ V5.x||DEC C++ V6.0|
|DEC COBOL V2.4, V2.5||Compaq COBOL V2.6|
|DEC Pascal V5.0-2||DEC Pascal V5.1-11|
V3.1 for OpenVMS Version 7.1-2
V4.1 for OpenVMS Version 7.2
|MACRO--64 V1.2||See below.|
Current versions of the MACRO--64 assembler may still encounter the
loop rotation issue. However, MACRO--64 does not perform code
optimization by default, and this problem occurs only when optimization
is enabled. If SRM_CHECK indicates a noncompliant sequence in the
MACRO--64 code, it should first be recompiled without optimization. If
the sequence is still flagged when retested, the source code itself
contains a noncompliant sequence that must be corrected.
8.6 Recompiling Code with ALONONPAGED_INLINE or LAL_REMOVE_FIRST Macros
Any MACRO--32 code on OpenVMS Alpha that invokes either the ALONONPAGED_INLINE or the LAL_REMOVE_FIRST macros from the SYS$LIBRARY:LIB.MLB macro library must be recompiled on OpenVMS Version 7.2 or later versions to obtain a correct version of these macros. The change to these macros corrects a potential synchronization problem that is more likely to be encountered on newer processors, starting with Alpha 21264 (EV6).
Source modules that call the EXE$ALONONPAGED routine (or any of its variants) do not need to be recompiled. These modules transparently use the correct version of the routine that is included in this release.