On 30/04/02 at 23:01 henk verbeek wrote:
> Does anyone know how to upgrade the memory of a standard (classic) ql ? I
> have searched the net but i didn't find a circuit or anything. Are there
> no do it yourself circuits available ?
Done it many times in many ways. By far the simplest is to find a 628512
(aka 614000) static RAM chip, usually comes in a 32-pin surface mount
package but regular DIP 32 is also available. This is 0.5MB in a single
very low power chip. In addition, you need two 100nf capacitors, one
74HC153 logic chip and one 1N4148 diode.
Here is the connection (use fixed width font)
74HC153
+--\__/--+
GND ----->|1 16|====== +5V
A19*----->|2 15|<----- GND
+5V ----->|3 14|<----- A18*
DSL*--o-->|4 13|<----- GND
+-->|5 12|<--o-- +5V
+5V ----->|6 11|<--+
RAM(A) <--|7 10|<----- GND
GND ======|8 9|--|>|-> DSMCL*
+--------+ A K
+--\__/--+
A18* ---->|1 32|====== Vcc
A16* ---->|2 31|<----- A15*
A14* ---->|3 30|<----- A17*
A12* ---->|4 29|<----- RDWL*
A7* ---->|5 28|<----- A13*
A6* ---->|6 27|<----- A8*
A5* ---->|7 26|<----- A9*
A4* ---->|8 25|<----- A11*
A3* ---->|9 24|<----- RAM(A)
A2* ---->|10 23|<----- A10*
A1* ---->|11 22|<----- RAM(A)
A0* ---->|12 21|<----> D7*
D0* <--->|13 20|<----> D6*
D1* <--->|14 19|<----> D5*
D2* <--->|15 18|<----> D4*
GND ======|16 17|<----> D3*
+--------+
* - signals from the expansion port, all but DSMCL can be found on the
68008 cpu, all but DSMC, DSL, RDWL, A19, 18, 17, 16 can be found on the ROM
slot or either ROM socket. The ROM sockets have the advantage of having the
correct pinout if the bottom of the chip is alligned with the bottom of the
socket (socket pin 14 goes to chip pin 16), for all pins except RAM pin 3,
22, 24, 29 and 30.
Here is the ROM chip socket for comparison (both sockets are wired the
same):
+--\__/--+
+5V ---->|1 28|====== +5V
A12* ---->|2 27|<----- A14*
A7* ---->|3 26|<----- A13*
A6* ---->|4 25|<----- A8*
A5* ---->|5 24|<----- A9*
A4* ---->|6 23|<----- A11*
A3* ---->|7 22|<----- ROMOEH*
A2* ---->|8 21|<----- A10*
A1* ---->|9 20|<----- A15*
A0* ---->|10 19|<----> D7*
D0* <--->|11 18|<----> D6*
D1* <--->|12 17|<----> D5*
D2* <--->|13 16|<----> D4*
GND ======|14 15|<----> D3*
+--------+
If you want to put this RAM expansion into one of the ROM chip sockets
(plus the few extra wires you need), you can take both ROMs and put them
'piggyback' one onto the other, carefully solder the pins together (do this
with pins facing up so solder does not go onto the pins of the chip that
will plug into the socket), and plug the combination into any one of the
two ROM sockets.
100nF capacitors go between +5V and GND pins on 74HC153 (pins 8 and 16) and
on RAM chip (pins 16 and 32). RAM(A) points are all tied together, i.e. pin
7 on 74HC153 goes to pin 24 and pin 22 or RAM chip. The whole thing uses
negligible amounts of current and you can 'steal' the +5V off of pins 16 on
the 74LS275 multiplexers or pin 20 of the 74LS245 buffer ship. The RAM is
zero-wait and will go as fast as the CPU can go, about twice as fast as the
built-in 128k.
To make things easyer to connect, you can connect the address lines (A??)
and data lines (D??) to the chip in any order, as long as you never mix
address and data.
628512 can sometimes be found on older hard drives from WD and Quantum,
820M or 1-2G capacity, normally near the IDE connector. They will be
surface mount as a rule. With these, one has to be carefull because they
come either in the normal case (pinout as above) or the 'reverse bent' case
with different markings (left and right side of the pinout are changed
around).
A variation of this circuit is possible where it is on a small piece of
printed circuit that plugs into the CPU socket, then the CPU itself plugs
onto that.
With some more logic, more RAM chips and a 68008FN CPU (in a PLCC 52 case
instead of the standard DIP48) it's possible to add almost 4M of RAM but it
will only work with some JS (and JS based) ROMs and Minerva.
Nasta
