Hello John !

Mod. 77 ... oh, yes - I vaguely remember that bit. 
Have cleared my offline-reader some time ago and obviously this message got lost. 
But no problem.


Basically the Mod. 76 and Mod. 77 differ by the case:
Mod. 76 is a small desktop with 3 slots and 1 5.25"-bay
Mod. 77 is a large desktop with 5 slots, 2 x 5.25" bays.


There are two different families of 76/77:


The old series had:
- onboard IBM SCSI with 60-pin external connector (half-pitch Mini Centronics)
- SCSI-harddisk
- XGA video system (card)
- Maximum 32MB RAM onboard
- 2 serial / 1 parallel connector
- 25MHz or 33MHz sysboard (oscillator select-jumper on 25MHz-board)
- uses only Parity Memory 2,4,8MB / 70nS
- the BIOS is fixed in an EPROM and not upgradeable

The later 76i / 77i had:
- onboard IDE-controller plus additional SCSI-card (iS-models)
- IDE-harddisk (i-models) or SCSI-harddisk (iS-models)
- onboard S3-928 SVGA video system
- 2 serial / 1 parallel connector
- optional 2nd Level cache connector
- Maximum 64MB Ram onboard
- support for DX4-cpu (3.45V with Voltage Regulator Module FRU 06H3011)
- supports Parity or ECC memory 4,8,16MB / 70nS
   (but logically no combination of both)
- the BIOS is Flash-EPROM based and upgradeable ("Lacuna-BIOS")


The easiest way to differ which is which is looking at the rear of the machine:

If it has 2 x 9 pin male comms, 1 x 25 pin female printer and 1 x 60 pin Mini-Centronics then it is the old 76 / 77.

If it has 2 x 9 pin male comms, 1 x 25 pin female printer and 1 x 15 pin Video then it is the later 76i / 77i. 
If there is a card installed with 50-pin high density Sub-D then there is an additional SCSI-adapter installed and machine will most likely be 76iS / 77iS.


I hope this is the information you are looking for.

Very friendly greetings from Peter in Germany
http://members.aol.com/phwimage1/mcaindex.htm
"Master Of Desaster" - PS/2 expert since 1987 (Sigh !)