DECpc 325 General Maintenance
.jpg)
Battery, configuration and routine care for the DECpc 325 (DECpc 325sxLP), from DEC's DECpc 320sxLP/325sxLP User's Guide (EK-DECSX-UG.003) and Technical Reference Manual (EK-DECSX-TM-001), the DECpc 325 User Disk, and David Hall's notes on two surviving machines.[1][2][3]
CMOS battery
[edit | edit source]The CMOS RAM that holds the configuration, time and date is battery-backed. DEC expected the battery to last at least three years; when it fails, the BIOS shows "Clock chip lost power" at power-on and the configuration has to be entered again.[4]
Hall reports that the machines shipped with a Rayovac 840 4.5 V alkaline battery fixed to the system board with Velcro next to the power connector, and that it leaks and does serious damage. He advises removing it on sight.[3] See Battery Explosion, Capacitor or Corrosion Damage for cleaning up alkaline leakage.
DEC's replacement procedure:[4]
- Find the battery and its connector using the motherboard diagram (Figure 6-2 in the user's guide).
- Peel the battery off the Velcro strip and unplug its cable from the motherboard.
- Fit the new battery to the Velcro and plug in the cable, making sure the wires are not crossed.
- Restart, enter Setup and enter the configuration again.
DEC's warning: the battery must not be recharged, taken apart, heated above 60 °C, exposed to water or soldered directly.[4]
Hall's notes on the circuit: the battery plugs into J8, with the positive pin at the end nearest the IDE connector. It feeds the VBATT pin of the 82C331 bus controller through diode D6, which drops about 0.56 V; the 82C331 datasheet allows 2.4–5.25 V at VBATT. Because of the diode, a battery connected the wrong way round does no damage but does not work. Hall replaced the original with three lithium AA cells, about 5.4 V open circuit, giving about 4.8 V at VBATT.[3] For building a replacement pack see Battery Refurbishment.
Saving and clearing the configuration
[edit | edit source]DEC's User Disk can save the CMOS contents to a file, CMOS.DAT, on the disk: Utility Setup, then Define configuration, then Save CMOS data. The same menu restores it. DEC warns that saving overwrites any earlier CMOS.DAT, so check the configuration is correct before saving.[5]
Jumper J7 on the system board clears the CMOS: pins 1 and 2 shorted for normal operation, pins 2 and 3 shorted to discharge.[6]
| Jumper | Function | Settings (default first) |
|---|---|---|
| J1 | COM2 address | 2F8H: 1-2, 4-5. 238H: 2-3, 4-5. Disabled: 2-3, 5-6 |
| J2 | On-board floppy controller | Enabled: 1-2. Disabled: 2-3 |
| J3 | COM1 address | 3F8H: 1-2, 4-5. 338H: 2-3, 4-5. Disabled: 2-3, 5-6 |
| J4 | On-board IDE | Enabled: 1-2. Disabled: 2-3 |
| J5 | LPT1 address | 278H: 1-2, 4-5. 378H: 1-2, 5-6. 3BCH: 2-3, 4-5. Disabled: 2-3, 5-6 |
| J6 | Display adapter | VGA/EGA/mono: 1-2. CGA: 2-3 |
| J7 | CMOS discharge | Normal: 1-2. Discharge: 2-3 |
| J9 | Monitor type | Colour: 1-2. Mono: 2-3 |
| J10 | Interlaced or non-interlaced | Interlaced: 2-3. Non-interlaced: 1-2 |
| J11 | On-board VGA | Enabled: 1-2. Disabled: 2-3 |
| J17 | 387SX coprocessor clock | Synchronous: 1-2. Asynchronous: 2-3 |
Hall enters Setup with Ctrl+Alt+S; the BIOS gives no prompt for it.[3] Fixed disk type 48 takes user-entered cylinder, head and sector values, and the BIOS has no LBA support.[3]
Memory
[edit | edit source]The SIMM sockets are angled at 45° so the modules overlap. Fit the bottom module first, then the others in order, each overlapping the one before; seat each module upright with its components to the front and press it down until the latches click.[7] DEC specifies 80 ns or faster 9-bit parity SIMMs.[8] Hall reports that modules go in pairs starting from bank 0, and that when 1 MB and 4 MB modules are mixed the 1 MB modules go first.[3]
Power button
[edit | edit source]The power switch is inside the supply and the front button reaches it through a linkage. A short rubber sleeve keeps the linkage aligned with the switch; Hall has found it perished on every machine he has seen, so the button stops working. He made a replacement sleeve from rolled paper and tape.[3]
Care and environment
[edit | edit source]- Operate between 10 and 35 °C and 20 to 80% relative humidity, non-condensing.[9]
- Do not stand the system unit on its side, and do not move it while the power indicator is lit.[10]
- Use an outlet that does not also power copiers or other high-current machines.[10]
- The User Disk's GOSLOW utility drops the processor from 25 MHz to 8 MHz for speed-sensitive software, and GOFAST restores it.[5]
Related pages
[edit | edit source]- DECpc 325
- DECpc 325 Troubleshooting Guide
- Battery Explosion, Capacitor or Corrosion Damage
- Battery Refurbishment
- Hard Drive Maintenance and Repair
References
[edit | edit source]- ↑ Digital Equipment Corporation, DECpc 320sxLP/325sxLP User's Guide, EK-DECSX-UG.003, June 1992 (File:DECpc 320sxLP 325sxLP User's Guide (EK-DECSX-UG.003).pdf).
- ↑ Digital Equipment Corporation, DECpc 320sxLP/325sxLP Technical Reference Manual, EK-DECSX-TM-001, March 1992 (File:DECpc 320sxLP 325sxLP Technical Reference Manual (EK-DECSX-TM-001).pdf).
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 David Hall, "Digital DECpc 320sxLP/325sxLP", zxnet, last modified 31 May 2024, zx.net.nz.
- ↑ 4.0 4.1 4.2 DEC, DECpc 320sxLP/325sxLP User's Guide, EK-DECSX-UG.003, p. 6-13, section 6.4.5, "Replacing the Battery".
- ↑ 5.0 5.1 Digital Equipment Corporation, DECpc 325 User Disk, version 1.00, files README_U.HLP and SETUP_U.HLP (English sections), archive.org.
- ↑ 6.0 6.1 DEC, DECpc 320sxLP/325sxLP Technical Reference Manual, EK-DECSX-TM-001, p. 3-7, Table 3-1, "Configuration Setting".
- ↑ DEC, DECpc 320sxLP/325sxLP User's Guide, EK-DECSX-UG.003, pp. 6-8 to 6-9. SIMM installation and removal.
- ↑ DEC, DECpc 320sxLP/325sxLP Technical Reference Manual, EK-DECSX-TM-001, p. 2-2, Table 2-1.
- ↑ DEC, DECpc 320sxLP/325sxLP User's Guide, EK-DECSX-UG.003, p. 8-2. Environment.
- ↑ 10.0 10.1 DEC, DECpc 320sxLP/325sxLP User's Guide, EK-DECSX-UG.003, pp. 3-4 to 3-5. Installation cautions and front panel.