Third-Party Disk Controllers

Overview

Mass storage technology has evolved over the years, with each new mechanical storage product quickly becoming obsolete after just a few years of being on the market. For the hobbyist, like myself, this makes resurrecting old computers more difficult. I have little interest in owning a pair of RL02 disk systems, or an RA80 drive. These are large, noisy units and are all beyond their useful life. About the only storage standard that has some usefulness left is SCSI.

A number of manufacturers made fast, narrow, high-voltage SCSI controllers for the Q-bus line of machines. These controllers can still be adapted to support modern storage technologies, through the use of bridge controllers. The table below contains a comparison of some of these controllers. Many of these controllers are difficult to find, as is their documentation, in some cases.

Emulex

Manufacturer	Emulex	Emulex	Emulex	Emulex
Model Number	UC04	UC06	UC07	UC08
Introduced
Discontinued
Module Size	Dual	Dual	Dual/Quad	Quad
Q-bus Addressing	22-bits	22-bits	22-bits	22-bits
Disk Support	MSCP¹	MSCP¹	MSCP¹	MSCP²
Tape Support	TMSCP¹	TMSCP¹	TMSCP¹	TMSCP²
SCSI Busses	1	1	1	2
Single/Diff.	Single	Diff.	Single	Single
Synchronous Transfers	no	yes	yes	yes
Async Transfer Rate	2 MB/s	2 MB/s	2 MB/s	2 MB/s
Sync Transfer Rate	N/A	2 MB/s	2 MB/s	2 MB/s
Largest Disk	8 GB	8 GB	8 GB	8 GB
Partitioning	no	yes	yes	yes
Partitions	N/A	2	2	2
AC Bus Load	2.5	2.5	2.5	2.5
DC Bus Load	1	1	1	1
+5V Load	2.6 A	2.3 A	2.3 A	4.5 A

¹ The SCSI bus cannot simultaneously support disk and tape devices.
² The SCSI buses themselves cannot simultaneously support disk and tape devices, but one bus can be configured for disk devices and the other for tape devices.

California Micro Devices (CMD)

Manufacturer	CMD	CMD	CMD	CMD	CMD	CMD
Model Number	CQD-200/M	CQD-220/M	CQD-240/M	CQD-260/M	CQD-420/M	CQD-440/M
Introduced
Discontinued
Module Size	Dual	Dual	Quad	Quad	Dual	Quad
Q-bus Addressing	22-bits	22-bits	22-bits	22-bits	22-bits	22-bits
Disk Support	MSCP¹	MSCP¹	MSCP¹	MSCP¹	MSCP¹	MSCP¹
Tape Support	TMSCP²	TMSCP²	TMSCP²	TMSCP²	TMSCP²	TMSCP²
SCSI Busses	1	1	1	1	1	1
Single/Diff.	Single	Single	Both	Both	Both	Both
Synchronous Transfers	no	yes	yes	yes	yes	yes
Async Transfer Rate	3 MB/s	3 MB/s			7 MB/s	7 MB/s
Sync Transfer Rate	N/A	4.8 MB/s			10 MB/s	10 MB/s
Partitioning	no	yes	yes	yes	yes	yes
Partitions	1	2,4³	2,4³	2,4³	2,4³	2,4³
AC Bus Load
DC Bus Load
+5V Load	2.0 A	2.0 A			2.0 A⁴	3.5 A

¹ Only the /M and /TM models.
² Only the /T and /TM models.
³ Partitions are equal size.
⁴ Differential mode. 1.5 A in sigle-ended mode.

Summary

The Emulex UC04 is an early version of the UC07 and is generally considered to be buggy. The UC06, UC07 and UC08 controllers are solid, about 95% comaptible with existing software, and somewhat versatile. Based on personal experience, these controllers only have 24-bits of LBA addressing, which limits them to 8GB per disk.

The CMD controllers are very popular, and extremely simple to setup and use. These controllers have more compatability issues than the Emulex controllers, but work extremely well, otherwise.

References

Emulex UC04 Intelligent Host Adapter Technical Manual, February 1986 (UC0351002, Rev A)
Emulex UC06, UC07 and UC08 Intelligent Host Adapter Technical Manual, November 1990 (UC0751001-00, Rev H)
CMD CQD-200/203 Qbus Controller Installation Guide, April 1996
CMD CQD-220/223 High Performance Q-Bus Sync/Async SCSI Host Adapter User's Manual, Rev 2.5, November 1990
CMD CQD-220A/223A High Performance Q-Bus SCSI-2 Smart Host Adapter User's Manual, Rev 1.1, December 1993 (MAN-00220A-000)
CMD CQD-420/423 High Performance Q-bus FAST SCSI-2 Smart Host Adapter User's Manual, Rev 1.5, May 1994 (MAN-000420-000)

Additional Resources

MicroNote 12 - DMA on the Q-bus

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