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

Axil S/420 Workstation
and
Axil S/420 Server

System

The S/420 is a SPARCstation-20 compatible, providing the full quota of two MBus slots. The memory controller is a custom Axil ASIC (supporting upto 1Gb RAM across 16 SIMM sockets), as is the MBus-SBus interface chip.

The MBus in the S/420 is autoswitched to either 40/50MHz, just like the SPARCstation-20.

The "Server" configuration is the same as the "Workstation" with the addition of an external SBus expansion-box, see the pictures. The expansion-box also houses additional disk drives.

Firmware Revisions

I have no information on the available S/420 BootPROMs.

The S/420 may not support all the modules that the SPARCstation-20 does, depending on available Axil BootPROM revisions.

Overheating

Internally, the S/420 "upper" chassis is very similar to the SPARCstation-20 with the exception of the tightly-packed 16 SIMM sockets (instead of 8) and the extra fan alongside them.

On balance, I would expect the S/420 to be at least as heat-resistant as the SPARCstation-20.

Other Issues

Double-width modules will block one SBus slot each. Whether such modules work or not in the S/420, has yet to be determined.

MBus Module Configuration Table

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

Module Type No. of
(identical)
Modules		 Functional? Min. PROM level Heat Rating
SM100
SM20
SM21
SM30
HMx1S-256		 1 no n/a n/a
2
SM41
SM50
SM51
SM61		 1 yes any safe
2
SM51-2
SM61-2		 1 yes, but only uses
1Mb of the 2Mb per-module
SuperCache		 any safe
2
SM512 1 unknown, and each module
would block an SBus slot		 unknown safe
2
SM52 1 unknown, and each module
would block an SBus slot		 unknown safe
2 harmful?
SM71
SM81		 1 yes any? safe
2
HM55any
HM66any
HM72any
HM80S-256
HM90any
HM100any
HM110D-256
HM125S-256
HM125D-256
HM150S-256		 1 yes any? safe
2
HMany-512
HMany-1024		 1 unknown unknown safe
2

Introduction Buses Modules Systems Chips Miscellany
Mike Spooner, revised 9th June 1999