New design and release of SAMS memory expansion boards for the TI-99/4a. NEW 2017 MODEL now shipping adds a couple new chips 74ls373 and an additional 74ls08

This iteration of the layout will only work in 1MB mode. No parts or sockets included, you must source those yourself. The board is clearly labled for each part. Assembly is required!

SuperAMS (Super Asgard Memory System, a.k.a. SAMS card) was one of the first "memory expansion"
cards designed for the TI-99/4A. It was designed around 1993 by Asgard Inc, under the management of Jim Krych. Its elegant simplicity is due to the fact that it's build around the 74LS612 memory mapper, once commonly used in PCs and in Nintendo game cartridges.

Advice from the manufacturer:

1. Don't worry about using 36-pin sockets for the memory chips. Just use a 32-pin positioned to ignore the four pins closest to the 74LS612.

2. So far, about one in four of the 74LS612s I've received from various sources were bad. Being able to test LS logic chips (many EPROM burners do this) is a very good thing that will save you a lot of hair-pulling. I've had other chips that were bad too, but the 612s seem to be the most common when it comes to problems.

3. The 74LS688 chips can be replaced by a 25LS2521. These are a drop-in replacement for the 74-series chip, and appear to be a bit easier to find.

4. Do not try to put these boards into a TI Clamshell. There are traces that will short out because of protrusions on the inside of the clamshell designed to hold TI cards stable. This is one of the reasons you see no mounting or other holes in this board, as it discourages attempts that would damage it. The PEB tabs are another deterrent here.

5. The right-angle mounted LEDs that I initially received could only be installed on the bottom of the board to get their polarity correctly aligned. They don't get in the way of any other cards and work fine when installed that way. Other LEDs with standard leads won't have this issue, and neither will vertically mounted LEDs similar to the right-angle ones from my initial builds.

Parts List:

5x 0.1uf tantalum capacitors

1x 47uf electrolytic capacitor

1x 100uf electrolytic capacitor

1x 220 ohms resistor ( I'm assuming a 1/4watt will do for both resisters )

1x 22uf tantalum capacitor

1x 1k ohm resistor

1x 7805 voltage regulator

1x heat sink for voltage regulator

1x LED

1x 74LS125 Quad bus buffer ic

1x 74LS138 3 line to 8 line decoder ic

1x 74LS32 Quad 2-input OR gate ic

1x 74LS04 Hex inverter ic

1x 74LS612 memory mapper ic

2x 62512 SRAM ic or equiv.. here's a stocked part https://www.mouser.com/ProductDetail/Alliance-Memo...

1x 74LS259 8 bit addressable latch ic

1x 74LS08 Quad 2-input AND gate ic

3x 74LS244 Non Inverting Buffer/Driver ic

1x 74LS688 8 bit magnitude/identity comparator ic ( Noted alternative: 25LS2521 )

1x 74LS245 Octal Bus Transceiver ic

1x 555 timer ic

1x 8pin dip socket ( 2x4 )

1x 40pin dip socket ( 2x40 )

2x 32pin dip socket ( 2x16 )

4x 14pin dip socket ( 2x7 )

2x 16pin dip socket ( 2x8 )

5x 20pin dip socket ( 2x10 )

and a bit of thermal compound for the heat sink.