Good Morning Everyone.

I´ve tried to upgrade my FS-A1ST memory to 1 Mb using JIPE/HANSO circuit located at http://msx.retro8bits.com/msxdocs/msxturbor1mb.pdf

I´m using 2 memory ICs type TMS44400, with 60 ns access time, extracted from a SIMM-30.

The problem is that, after the upgrade, the MSX won´t boot anymore.

I´ve double-checked the circuit and pinouts, and everything is exactly accordinly to JIPE instructions.

Does anyone have an ideia of would could it be?

Thanks in advance;

Fernando - Brazil

Well, looking to the diagram for ST I would say there should be no reason for such behaviour because all other relevant schematics stay in place without modifications - /RAS, /CAS and /WE. Check again, you should have done something wrong, and most probably with LS367 so it has steady low level at the output and hangs data bus's bit 5 (this is actually the only one output of this schematic!).

Another suspicion is 60 versus 70ns, wrong timing also can be the cause for non-operation (however I checked refresh timing should be the same). If you prove that you wired everything correctly and the circuit does not hang any lines, then it would probably be memory chips. BTW, they sometimes die (for example, from static electricity).

the board with 74LS670 is optionnal with DOS2 just for decode mapper for DOS1

if you cut wire pin 18 R800 to ground , shunt 22 S1990 to 18 R800 , shunt 33 R800 to pin 5 memory , sold resistor 1K on R41 , sunt R229 , desold R206 , shunt R206 with A14 and sold memory the ST start

can you make photos of modification and memory

added : the ST work with 60ns but not the GT (required 70ns)

id like to see detailed pictures of it to

Thanks for your feedback my friends.

I believe that I´ve probably bricked it somehow through the installation process, because I´m trying now to insert the original 256k back to the sockets that I´ve installed, and it doesn´t seem to work.

Also, I´ve tried with different 70 ns and 60 ns simm-30 that I have, and nothing as well.

I´ll take some high-def pictures, and will record a you-tube video of the t-R behavior this weekend, and will post it here, so you could try to help me to figure it out where it could be the problem.

Thanks in advance;

check your wires between memory , a past i have breaking wire then desold memory , if breaking make a shunt

jipe
could you make a dumb list for me?
connect wire from r1 to r 4
connect pin 2 to pin 4
cut pin 6 of IC 35

something simple like that?
i dont need to know what im doing, i just need to know what i need to do

thanks


oh
and hi-res pics would help too

is not easy to make a quickly dumb list because i have not a Turbo-R open near me and some signal don't connect to a composant but directly on a hole in board
you can see hi-res picture in hnostar n°43 july 1999

if you mount directly chips a special shunt is required R373 left connect to R372 right with a cms resistor
is for bank 0 of R800 memory ( is on Hanso PDF )

and IC31 pin 5 , IC32 pin 5 must be connected to IC30 pin 5 ( is not on Hanso PDF )

the first schematic is for a simm 30 ( see on hnostar ) and modified for direct chips

heh
i dont understand a word youre saying

composant
shunt?
cms resistor?
r800 memory?


i have no idea

but its not important
if you can make me such a list id be very gratefull
it doesnt have to be tomorrow or next week

sorry i'am french i my english is very poor

composant is a electronic spare
shunt is a little wire nude
cms is "composant monté en surface" in french
on Turbo-R the memory chip is directly on R800 bus
see schematic on Hanso web
if you cannot read a schematic , not modify your MSX because you don't find error or breaking wire after

i have same difficult for understand the english post and babel fish don't help for technical language

Quote:

cms is "composant monté en surface" in french

SMD component then

Jipe> Since you seem to understand all this stuff, I have a theory I want to have checked by someone with actual knowledge of electronics.

I was wondering about the 1MB limit. This limit comes from the number of address lines available from the S1990. Which is what handles the memory mapper for the main RAM. However, wouldn't it be possible to recreate the mapper circuitry outside the S1990 by connecting to the IO pins directly (like any external mapper would do). Normally port IO writes are not slot sensitive and could be processed by device. However, it may be that all IO is routed through the S1990 (most likely since something needs to manage the two cpus) and it actively blocks writes to #FC-#FF when the pages are in main RAM. But it seems to me that you should still be able to process it directly from the IO lines.

I don't really have any idea how read back of #FC-#FF is managed, but it seems less important since this doesn't work properly even with 1MB.

Anyway, do you think that something like this could result in 4MB internal memory? Or is it impossible due to some issue that I have no knowledge about?

the history : i find 1Mo schematic in a japan files and the adapt for 1Mo mapper in a GT buy by a friend in Deutchland

i just adapt the board for GT and ST with a Simm and make other adapt memory long time after for other friend

i learn electronic himself and my knowledge is by working and working (with a good help by Proteus simulation)

hey Jipe or anyone that can answer that:

Does the FS-A1-ST boot normally with the keyboard cables and the upper case cables (LEDs and controls) all disconnected?

I´ve tried to do that.. so maybe that´s the reason it burned... who knows?

Thanks.

if you connect external mapper does it boot ?
when you say dont boot , it means screen stays black or it light on and then shortly hangs ?

if the screen stays black : you probably have shot circuit sinking current and maybe burnt
something.

if the screen light on : it means rom code is executed but ram is not found for some reason.

I would say any msx i have opened booted even with leds and keyboard disconnected.

I got sometimes problems by removing disk drive on some msx i guess it is related to shielding ( blindage )
removing that goes with top cover .


Just for info : i am electronic engineer , i made so many year studying , i changed a handfull msx's like vdp9958, turbo 7Mz , RGB encoder repair , building cable , internal ram expansion.
My conclusion : you need at least 2000 euros of hardware/oscilloscope /meters around to debug&repair know what you are doing and even like this i burned 2 msx's-> i dont think i would modify my turboR ever.
i would also plan 2 full days to feel relaxed and not feel urged to do everything i one morning between breakfast and noon.
optional conclusion : i am poor electronician ...
optional conclusion 2 :sometimes you need luck ...

@jipe , your english is not so bad