Rev 0.2: Fixes initial revision bugs

- Supports second type of voltage regulator
- Hole pads are now a little larger

Author: ScrapComputing

.gitignore

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+/kicad/*-cache 
+/kicad/*-cache.lib 
+/kicad/*-bak
+/kicad/gerbers/*

LICENSE

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+# 486SocketBlaster
+
+486SocketBlaster is a simple voltage adapter for 486 processors. It allows you
+to use a 3-volt 486 CPU on an older 5-volt-only motherboard. For example you
+can use a DX4 or an Am5x86 on an old 486 motherboard that would normally only
+work with 5-volt CPUs. This basically converts any 3-volt CPU to an "Overdrive".
+
+<img src='img/486SocketBlaster_rev0.1.jpg' alt='486SocketBlaster Rev0.1 on a purple PCB' height=240>
+
+<img src='img/486SocketBlaster_pcb.png' alt='486SocketBlaster PCB' height=240>
+
+# How does it work ?
+
+It is really simple: All CPU pins are passed through to the motherboard socket,
+except the Vcc ones. Those are connected to the output of a mini buck converter
+that can be soldered to the 486SocketBlaster board.
+
+# Soldering/Assembly Instructions
+
+This board is tricky to solder, but can be done with a standard soldering iron.
+The best way to solder the headers is to start with the innermost one and work
+outwards in a spiral manner alternating between the top and bottom side as
+needed. This way you only work on the outside.
+
+A desoldering gun may be useful when you accidentally clog up other holes.
+Also using flux makes it easier.
+
+Please make sure you check for continuity before you add another row of headers
+on the same side, because the new row will permanently block your access to the
+solder joints! Desoldering a header is *extremely* difficult even with a
+desoldering gun due to the tight hole tolerances.
+
+# Voltage regulator
+
+The 486SocketBlaster can be powered by a cheap of-the-shelf buck converter, or
+by an external one. The circuit board accepts two common types of small voltage
+buck converters, usually found using keywords like "mini buck converter".
+These are commonly rated at up to 3A of current. Given that 3-volt 486 CPUs are
+usually very efficient (the DX4-100 is rated at max 3.55/5.22W typical/max) such
+a regulator should be adequate in most cases.
+
+If you are planning to overclock or to use a more power hungry CPU, please use
+an external regulation circuit.
+
+# WARNING!!!
+
+Please make sure you know what you are doing!
+Improper assembly/settings/use can damage both your precious motherboard and your precious CPU!
+
+# Bonus Features
+
+- Header for an external voltage regulator, or for monitoring the voltages.
+- Header for selecting/overriding the CPU multiplier. This may be useful for
+reducing the multiplier of a DX4 or Am5x86 CPU.
+
+# Bill of materials
+
+Item                            | ##  | Description
+--------------------------------|-----|--------------------------------------------------------
+mini buck converter             | 1   | We support two common sizes: 22x17mm and 18x12mm. These usually have chips like MP1584, MP2307 and others
+40pin SIP pin header (male)     | 5   | Single-row round pin 2.54mm pitch (male). Socket pin diameter: 0.5mm, PCB pin diameter: 0.6mm. (see photo below)
+40pin SIP socket header (female)| 5   | Single-row round pin sockets, 2.54mm pitch. PCB pin diameter: 0.5mm. (see photo below) 
+SMD Capacitors                  | 4   | 0.1uF SMD 1206
+Throughole Capacitor            | 1   | 1uF ceramic through-hole capacitor
+3-pin header 2.54mm             | 1   | Header used for selecting the CPU Multiplier
+Jumper 2.54mm                   | 1   | A jumper to for the 3-pin header
+
+The capacitors seem to be optional, at least with the limited testing that I
+have done so far. Depending on they quality of the buck converter they may
+or may not improve stability.
+
+![headers](img/headers.jpg)
+