The Rough Guide to MBus Modules
Introduction Buses Modules Systems Chips Miscellany

SPARCstation-10

(including the model 20)

System

The SS10 system bus is a 33/40 MHz MBus (on the model 20) or a 36/40 MHz MBus (other models), with 2 slots for plug-in CPU modules.

Configurations using a single module must locate that module in slot 0 (the lower one).

Firmware Versions

Older systems may require BootPROM upgrades to be able to use newer MBus modules. Where known, the minimum BootPROM level is listed in the module configuration table.

The last available BootPROM is version 2.25 from Sun, or 2.25R from Ross/Bridgepoint.

WARNING:
The 2.25 and 2.25R PROMs have real behavioural differences.

The Ross 2.25R PROM enables 32Mb DSIMMs and RT620D-based HyperSPARC modules. The Sun 2.25 PROM does not.

The Sun 2.25 PROM works with SM20, SM30, SM52X; and (at least in part) with SM520, SM51-2, SM61-2, SM81-2 and pairs of some SM40 modules. The Ross 2.25R PROM might not.

There may be other differences.

The Ross 2.25R PROM can often be distinguished by the word "splug" on the label.

Overheating

The SS10 enclosure is somewhat prone to overheating.

Also, an SS10 fully populated with hot MBus modules and SBus cards and DSIMMs may overstress its' 140W power-supply (eg: an SS10 with two SM81 modules, a twin-slot SBus AG10 framebuffer, a SunSwift SBus card, an SBus PCMCIA adaptor, a full quota of 512Mb RAM, two internal disk-drives, you get the picture).

Configurations rated as deadly should not be used without additional cooling (ie: external fans to boost the left-to-right airflow), nor in heavily-configured systems.

Configurations rated as very hot should not be used in fully-populated systems (see above) without great care, or at least some additional cooling.

Also, the ZX and TurboZX (Leo) SBus graphics cards generate a huge amount of heat; the TurboZX draws a mind-boggling amount of power from four (yes, power from all four) SBus slots. If you have a ZX or TurboZX card installed, you should avoid configurations rated very hot; in the case of TurboZX, you should also avoid configurations rated merely fairly hot.

Similar precautions might be prudent if you have a Fujitsu AG-10 graphics card installed.

Prolonged disregard for the above guidelines is likely to result in damage:

NOTE:
The heat-ratings are normalised against an ambient air temperature of upto 30 Celcius. If the external air temperature is above 30 Celcius, you should take extra care.

The SS10 enclosure will also cook hot disk drives (eg: Seagate 1/3-height Barracudas). However, the drive bays are sufficiently far from the MBus slots, and sufficiently isolated by the redirected airflow from the third fan, that overheating disk drives should not contribute significantly to module-overheating risks (and vice versa).

System Jumper Settings

The SS10 system MBus speed-selection protocol is controlled by jumpers on the motherboard. There are two types of SS10 motherboard: the older ones have three clock-speed jumpers (J1401, J1403, J1404), the newer ones only have a single clock-speed jumper (J1401).

The appropriate MBus speed depends on the CPU modules installed, see General Module Configuration Rules.

MBus Clock
(model 20)		 MBus Clock
(other models)		 Older System-BoardNewer System-Board
33 MHz 36 MHz J1401: jumper
J1403: jumper on pins 2-3
J1404: jumper on pins 2-3		 J1401: jumper on pins 2-3
40 MHz 40 MHz J1401: no jumper
J1403: jumper on pins 1-2
J1404: jumper on pins 1-2		 J1401: jumper on pins 1-2

Other Issues

The SS10 has two rows of two SBus slots for peripheral expansion (SCSI cards, framebuffers, serial-port cards, etc). Each double-width MBus module blocks an SBus slot on a distinct row, reducing the maximum number of single-width and double-width SBus cards by one. Thus an SS10 with two double-width MBus modules would have room for upto two single-width SBus cards, and no room for double-width SBus cards at all.

Depending on the size of your fingers, it may be neccessary to temporarily remove the DSIMM in SIMM slot 0 whilst inserting or extracting a second MBus module. Bear in mind that the system will not boot unless SIMM slot 0 is populated, so the DSIMM should always be replaced in that same slot afterwards.

MBus Module Configuration Table

Specific part-numbers are only listed where significant.

See also: General Module Configuration Rules, which also covers mixed-module configurations.

Note: some configurations have particular caveats, such as failing to provide the level of performance that one might intuitively expect, or dangerous overheating, and so on. Such configurations are marked with a footnote-number in square brackets.

Module Type No. of
(identical)
Modules		 Functional? Min. PROM level
Model 20 Other Models
CYM6001K 1 yes [12] yes [12] 2.7?
2 no no n/a
SM100 1 yes yes 2.7?
2
SM20 1 yes no unknown
2 no no n/a
SM21 1 no no n/a
2
SM30 1 yes  [1] yes unknown
2 no no n/a
SM40
501-2219
501-2295
1 yes yes 2.7
2 no no n/a
SM40
501-2358
501-2570
1 yes yes 2.7
2 yes yes 2.12.2
SM41
(33MHz)
501-2318
1 no no n/a
2
SM41
501-1714
501-2258
501-2270
501-2359
1 yes yes 2.7.8
2 2.9.16
SM52 1 yes  [10] yes  [10] 2.9
2 yes  [11] yes  [11]
SM52X 1 yes yes 2.9?
2
SM520 1 yes  [8] yes  [8] 2.9
2
SM521 1 no no n/a
2
SM50 1 yes  [2] yes  [2] unknown
2
SM51
SM61		 1 yes yes 2.9.16
2
SM51-2
SM61-2		 1 yes  [7] yes  [7] 2.9.16
2
SM71 1 yes yes 2.22.1
2 yes  [9] yes  [9]
SM81 1 yes  [9] yes  [9] 2.22.1
2 yes  [10] yes  [10]
SM81-2
SM91-2		 1 yes  [7]  [9] yes  [7]  [9] 2.22.1
2 yes  [7]  [10] yes  [7]  [10]
HMx1S-256 1 unknown unknown  [6] unknown
2
HM55any-256
HM66any-256
HM72any-256
HM80S-256
HM90any-256
HM100any-256
HM110D-256
HM125any-256		 1 yes yes 2.19.3
2
HM110any-1024
HM125any-512
HM125any-1024
HM133any-512
HM142S-1024		 1 yes yes 2.25.0 and 2.25R
2
HM142W-1024
HM150S-512
HM166S-512		 1 yes yes 2.25.0 and 2.25R
2 yes  [9] yes  [9]
HM150D-512 1 yes yes 2.25.0 and 2.25R
2 yes  [10] yes  [10]
HM150W-512 1 unknown unknown (2.25.0 and 2.25R)
2 unknown  [9] unknown  [9]
HM180S-512
HM180D-512		 1 yes yes 2.25R
2
HMx4.5S-512 1 yes  [5] yes 2.25R
2
HMx4S-512
HMx4D-512		 1 yes  [3] yes  [4] 2.25R
2

Footnotes:
1.
CPU runs underclocked, at 33MHz.
2.
CPU runs underclocked, at 40MHz.
3.
CPU runs underclocked, at 144MHz.
4.
CPU runs underclocked, at 160MHz.
5.
CPU runs underclocked, at 162MHz.
6.
May require the MBus speed to be set at 36MHz (33MHz on model 20).
7.
Only 1Mb of the 2Mb per-module cache memory is used.
8.
In these systems, the SM520 behaves as a single-CPU module when using any Sun PROM. The behaviour with Ross 2.25R PROM is not known.
9.
Fairly hot. Generally OK, but see Overheating.
10.
Very hot. Safe enough if caution taken. See Overheating.
11.
Deadly. See Overheating.
12.
Although the CYM6001K module works in the SS10 at the hardware and MBus level, Solaris 2.4 and later releases do not quite work on such a configuration (Solaris boots, but hangs when attempting to access the internal disk). Earlier Solaris releases, or SunOS 4.x, may behave differently.
Introduction Buses Modules Systems Chips Miscellany
Mike Spooner, revised 1st November 2003