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ALT Upgrades
ALT DIP switch settings
PPC DIP switch settings
PPC Expansion bus connectors

One of the most common questions I'm asked is whether one can add a hard disk to the PPC. The fact is that it is technically possible (so is anything - eventually!) but I'd guess it might cost 500-1000 to do it and for the same money you can buy a decent end of line 386 portable with 100MB so what's the point?

Another thing I'm often asked is what are the DIP switch settings for ALT or PPC so here they are.

Upgrading the ALT/ACL

ALT/ACL memory

A lot of people write to ask if they can upgrade the memory in their ALT. The fact is that the chipset at the heart of that machine only has external address pins to allow it to address 4MB of memory so there is no way that it could ever use more than 4MB (back when the ALT was designed 4MB was considered to be huge! How times have changed eh?). The only possible upgrade is that if your ALT currently has just 1MB of RAM then you can remove the existing SIMMs and replace them with four 1MB 30 pin parity checked SIMMs to bring it up to the 4MB total (and set the DIP switches accordingly as shown below). The ALT design was very sensitive to the capacitance of SIMMs used and experience shows that 9 chip SIMMs almost ALWAYS work while more modern 3 chip almost NEVER work.

I don't think the ACL had such a limitation on memory upgrades but no longer have a user manual. When I can get the details from a current ACL user with a manual I will update this page with memory upgrade details for the manually challenged (like me!).

ALT/ACL processor

Another common question is whether the 286/386 in the ALT/ACL can be upgraded. The answer is a pretty simple "No". You can get 286->386 and 386->486 upgrade processors but these just physically will not fit inside the ALT case. You'd be best advised to trade in the ALT and look for a minimum of 486SX25 based laptop/notebook.

Later: The above was what I understood until recently when Phil Mordecai emailed me to say that he knows of an ALT that did have it's processor upgraded. The details are as follows: The processor was a Cyrix which clocked a 25MHz. It was obtained from and fitted by a company called Stratum Technology. They were out on the M40 near Beaconsfield and their number was (01734) 321900. I've no idea if they are still in existence but it may be worth trying them.

ALT/ACL hard disk

Naturally, the third upgrade option people ask about is a hard disk. The interface inside the ALT is IDE and the BIOS (which you access by pressing Ctrl-Alt-S at the C:\> prompt) will accept settable parameters for the drive so upgrading is farily plain sailing. I've heard from loads of people who've successfully added big drives. The only slight "gotcha" is that the BIOS does not support LBA so the theoretical size limit for an HD is 504MB but the likes of Ontrack's Disk Manager will easily get you past that and most modern large drives come with a free copy (check when buying!).

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ALT DIP Switches

ALT DIP switch settings (Bank A) are as follows:
Sw1=Off, Sw2=On, Sw3=On 512K memory
Sw1=On, Sw2=Off, Sw3=On 1MB memory (default)
Sw1=Off, Sw2=On, Sw3=Off 2MB memory
Sw1=On, Sw2=Off, Sw3=Off 4MB memory
Sw4 (ALT386SX Only) - Page mode - ALWAYS On
Sw5 - Wait states - ALWAYS Off
Sw6 - 8/16MHz clock - Off = 16MHz
Sw7 - Mono/Colour - On = Colour
Sw8 - Enable/Disable serial - On = Enable
Sw9 - (ALT386SX Only) - Pipeline - ALWAYS ON
Sw10 - Drive B: - type II - ALWAYS OFF
ALT DIP switch settings (Bank B) are as follows:
Sw1 and Sw2 ON = Onboard VGA enabled
Sw1 and Sw2 OFF = Onboard VGA disabled

(Only used if you install a different VGA adaptor in the expansion slot
- if you are using a monitor from the on-board VGA adaptor use the LCD
and CRT commands to switch between the two outputs - The DISPLAY
and SWITCHER utilities may als be used for this).

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PPC DIP Switches

PPC DIP switch settings are as follows:
Sw1 - Off = video output to LCD, On = video output to external connector
Sw2 - Off = Internal display adaptor acts as mono, On = act as colour
Sw3 - Off = internal display adaptor enable, On = disabled
Sw4 and Sw5 select the default video mode values programmed into the graphics adaptor.
Off, Off = External EGA
Off, On = CGA in 40 column
On, Off = CGA in 80 column
On, On = Mono mode
Setting of 4 and 5 must be consistent with Sw2 setting
Sw6 is unused
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PPC Expansion

Loads of people with a PPC email and ask what those "A" and "B" connectors on the back are for and if they can be used to expand the machine. Well, yes they do carry the main ISA bus signals. However be warned that the signals are totally unbuffered/unlatched so it is not as simple as just running the signals to the appropriate pins on an ISA slot. You've got to add supporting electronics. Back when the PPC came out two independent companies tried to make an ISA slot expansion box for the PPC and both failed but I don't now remember the technical reason why they had problems.

To my mind it just isn't not worth pursuing this in any way as the actual value of a PPC is pretty close to zero (A few quid maybe) so I'd just junk it and try and pick up a secondhand 386SX based laptop/notebook which is going to have the RAM and HD that you are after togther with a CPU that can run a half decent operating system (Win 3.1). But for the die hards I thought I'd type in the details from the now defunct PPC Technical Ref. manual about those connectors:

Expansion A is a 25 way D connector:

Num     Signal                          In/Out
===     ======                          ======
01      +5V DC                          In
02      T/C                             Out
03      I/O and mem address bit A19     Out
04      I/O and mem address bit A17     Out
05      I/O and mem address bit A15     Out
06      I/O and mem address bit A13     Out
07      I/O and mem address bit A11     Out
08      I/O and mem address bit A09     Out
09 *    I/O and mem address bit A07     Out
10 *    I/O and mem address bit A05     Out
11 *    I/O and mem address bit A03     Out
12 *    I/O and mem address bit A01     Out
13      AEN (Address Enable)            Out
14      Ground                          In
15      -Dack0                          Out
16      I/O and mem address bit A18     Out
17      I/O and mem address bit A16     Out
18      I/O and mem address bit A14     Out
19      I/O and mem address bit A12     Out
20      I/O and mem address bit A10     Out
21      I/O and mem address bit A08     Out
22 *    I/O and mem address bit A06     Out
23 *    I/O and mem address bit A04     Out
24 *    I/O and mem address bit A02     Out
25 *    I/O and mem address bit A00     Out

Expansion B is a 37 way D connector:

Num     Signal                          In/Out
===     ======                          ======
01      -20V DC                         --
02      IRQ2                            In
03      IRQ4                            In
04      IRQ6                            In
05      I/O Rdy                         In
06      -Dack2                          Out
07      -I/O Chck                       In
08      Dreq2                           In
09 *    CK14 (Osc)                      Out
10 *    -MemR (mem read)                Out
11 *    -IoR  (I/O read)                In/Out
12 *    ALE                             Out
13 **   I/O and mem data bit D7         In/Out
14 **   I/O and mem data bit D5         In/Out
15 **   I/O and mem data bit D3         In/Out
16 **   I/O and mem data bit D1         In/Out
17      -5V DC                          In
18      -12V DC                         In
19      Ground                          In
20      Ext power (+12V)                In
21      IRQ3                            In
22      IRQ5                            In
23      IRQ7                            In
24      -Dack1                          Out
25      -Dack3                          Out
26      Dreq1                           In
27      Dreq3                           In
28 *    -MemW (mem write)               Out
29 *    -IoW  (I/O write)               In/Out
30 *    Reset                           Out
31 *    CK4 (clock)                     Out
32 **   I/O and mem data bit D6         In/Out
33 **   I/O and mem data bit D4         In/Out
34 **   I/O and mem data bit D2         In/Out
35 **   I/O and mem data bit D0         In/Out
36      +12V DC                         In
37      +5V DC                          In

      A             B
  15......1   20..........1  (Seen from back)
   25...14     39.......21

Note that power pins (+5, -20, -5, -12, +12) are listed as inputs, this
means that power is to be supplied to, rather than drawn from these

The signals marked with an asterisk (*) after the pin number are
generated directly from the internal gate arrays and should be buffered
using a suitable non-inverting buffer (74HC244). There are 16 such

The signals marked with two asterisks (**) after the pin number are the
expansion data bus and are at CMOS levels. They should be pulled up to
TTL levels with 10K resistors.

All remaining signals are TTL compatible and can support a maximum
loading of six low power schottky (LSTTL) loads.

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