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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.
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!).
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.
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!).
(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). 
PPC DIP Switches
PPC ExpansionLoads 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
pins.
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
signals.
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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