PS/2 8550/8560 reference diskette v1.08
50Z by Mark Baker
PERSONAL SYSTEM/2 (R) MODEL 50 Z
ZM46,48 68X6143 PCBs with four NEC
|F1 LF 5MF 3A/250v
J1 Floppy riser slot
J2 Battery/speaker header
J4 Slot for Integrated Drive Ctrlr
J5,6 16 bit slot
J7 16 bit w/MME slot
J8 Case fan header
J9 HDD-15 VGA
J10 Parallel base
J11 DB25 serial
OS1 1.8432 MHz osc
OS2 25.17500 MHz osc
OSC3 28.32200 MHz osc
Q1 Motorola TIP120
Y1 32.768 KHz xtal
Y2 14.318 MHz osc
|Y3 4.0 MHz osc
ZM3 90X8134ESD DMA
ZM5 15F8365 BIOS Odd
ZM6 15F8366 BIOS Even
ZM8 Motorola MC146818A
ZM45 72 pin SIMM
ZM50 NEC D765AC-2
ZM68 INMOS IMSG171P-35
>and I don't have the key!!!!
Turn the unit with the rear facing towards you. Loosen
the thumbscrews - then use a *large* flat blade screwdriver to lift up
the cover about 3 mm over the lock position.
The inside lever goes only behind an edge of the case
... pry between case and rear wall and lift the case up a bit. Then
push the cover from the rear to the front.
When you have it open: pull the retainer bracket from
the lock assembly -
fumble it out and throw it away ...
Uses 85nS 1 or 2MB SIMMs
Zero wait state.
The 50-021 uses a proprietary MFM / ST-506 controller along
with a CMOS version of a MFM 20MB harddisk - and that's the only drive
supported on that controller. The 50-Z uses the MCA DBA-2 controller ...
usually they use ESDI-like auto-detection for the drive size and doesn't
use any tables (104xx error codes).
The 50Z-BIOS however has an "AT-style" table for the MFM
drives, which ends at Table ID 33 for the 30MB MFM-version of the MCA DBA-2
This table can be edited for larger MFM-drives (up to
500MB) with correcting the CRC checksum of the entire ROM pair. Did that
long time ago for a Mod. 60 to install a 350MB MFM drive. Basically you
can forget that stuff.
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