Front Panel Connector Pinout
Note: The matching pin header may have more pins than the plug in some cases. The later planars typically have 12-pin header, but they are still compatible with the 8-pin plug. Both the header and the plug are keyed to ensure correct installation.
Cases, Planars, and Riser Cards
You can upgrade any current PS/2 56/57 or 76/77 with the later "Lacuna" Planar. You'll gain all the advantages of the new 76/77 i and s systems. Current 76/77 systems will perform up to 38% faster while keeping everything else intact.
Note: Models 35 and 40 are ISA-based, and can't be upgraded with a MCA planar (the chassis is slightly different).There are two case types that were designed to accept the same planars:
The 855X had a planar based around the 80386DX or 80386SLC CPU. The newer 955X system were 486SLC2/SLC3 based. The first 9576 and 9577 systems used the same system board known as "Bermuda" (built-in SCSI). The later 9576/9577 i/s systems used a different board - called "Lacuna" (built-in IDE) and were available in two different clock speeds - 25 and 33 MHz.
The 76s/77s systems were the same as the 76i/77i units but they were equipped with a (modified) Future Domain SCSI card, to handle internal/external SCSI devices.
These models used the following riser cards (non-interchangeable, AFIK):
* CMOS battery located on riser card
So you see, it is important to know both the part number and clock speed limitation of the Lacuna-type board, and to have the correct bus riser card for the particular box/system board. In other words, you cannot really upgrade a 76/77 to a 76/77 i/s without changing the riser card as well as the system board!
Unit does not turn on (9556/57 9576/77)
Certain (Premium Line) models 9556, 9557, 9576 and 9577 have a security switch and will not run with the cover removed or if there is some problem with the switch.
The Security switch is built into the front of the base unit and interrupts the power-supply. It's easy to find - it is blue and sits somewhere left from the disk-drive bay.
It can be pushed with the finger gently upwards and to the inside - and the machine *should* run fine even without the case cover.
No need to be afraid: both - the power-switch as well as the security switch - operates at low voltage. They switch only a +5 V sense-line, not mains voltage.
But watch out: sometimes the security
switch flips back after some time or when you accidentally bump into the system.
The same switch is sometimes defective, after rude, careless people violently
push the case over the machine - or stuff the machine into the cover
respectively. It breaks and the machine won't power on.
PCMCIA Adapter mounting
I finally got around to installing the PCMCIA adapter in my 77s. The trick- mount the adapter on a 76/77 floppy tray. (Adapter MUST be in the stamped metal bay PN 64F1270) Remove the rail guides on the dive support structure in the 77. (Catches are on the inner end) swap the guides to the other side and push them onto the mounting studs. Now turn the tray/adapter upside down and push it into the rails. Note that the two card ejection buttons are now on the left side of the adapter. Just happens to be the exact height to perfectly fit the bezel.