Lambda 8300/Power 3000 Mutlirom

[1024MAK]

Looking good

Request for two PCBs sent via PM

Mark

[PokeMon]

I think the extension Lambda Multirom should work with my 32k RAM extension with following change:
Pin 4 of the 74HCT32 (IC6) should be connected to Vcc (+5V), Pin 14 of IC6.

xrammod.jpg (46.5 KiB) Viewed 24772 times

This will disable automatic RAM detection which is neccessary if you want to use other ROMs than original ZX81 ROM.
But you can still use 32k RAM - it will not be detected automatically, only 16k.
You can activate 32k if you enter POKE 16389,192 and after NEW.
Or you simply patch byte $0004 of the ROM from $7F to $FF for a full RAM test.
This is simple when creating self ROMs.

Code: Select all

                                            ;; START
    0000: [0000] D3 FD                      L0000:  OUT     ($FD),A         ; Turn off the NMI generator if this ROM is
                                                                            ; running in ZX81 hardware. This does nothing
                                                                            ; if this ROM is running within an upgraded
                                                                            ; ZX80.
    0002: [0002] 01 FF 7F                           LD      BC,$7FFF        ; Set BC to the top of possible RAM.
                                                                            ; The higher unpopulated addresses are used for
                                                                            ; video generation.
    0005: [0005] C3 CB 03                           JP      L03CB           ; Jump forward to RAM-CHECK.

This is not yet proofed by Sascha but should work, I think.

[sascha2000]

Hello,

I ordered today 24 PCBs. They will be produced within 3-4 weeks.

Price per PCB will be 7,74€ without components.

A component list I will provide soon here in this thread.

Best Regards
Sascha

[questarian]

I think the extension Lambda Multirom should work with my 32k RAM extension with following change:
Pin 4 of the 74HCT32 (IC6) should be connected to Vcc (+5V), Pin 14 of IC6.

Hmm... out of curiosity, sans the multirom, would your 32k extension work on a stock Lambda?

-John-

[PokeMon]

Hmm ... I think so, probably yes.
Since it is compatible hardware.
But you need maybe the same hack with "Pin 4 of the 74HCT32 (IC6) should be connected to Vcc (+5V), Pin 14 of IC6".

I don't have schematics of Lambda and not sure if the expansion slot is connected with all signals

[sascha2000]

Hello questarian,

>Hmm... out of curiosity, sans the multirom, would your 32k extension work on a stock Lambda?

I have tested the same. The 32k extension from pokemon does not work correctly on the Lambda without modifications.

Pokemon is working on this topic and as soon as he found a solution it will be posted here.


Here a picture what the Lambda displays with the 32k expansion:

http://forum.tlienhard.com/phpBB3/viewt ... =75#p10395

Regards
Sascha

[sascha2000]

Hello,

the multirom PCB is now finished and available. A first version of the manual is present here:

http://www.eightbits.de/Multirom/Manual-v005.pdf

It is beta and not finished!!!!! So please be patient and update will come soon.

Cause my time is currently very very limited I will process the orders in the following days like:

1) I will send all persons who have ordered a PCB a PN with my paypal account. I will du this successive person by person. Please be patient it can take some weeks until your order is processed.
2) When the money arrived I will ship the Multirom PCB ... normally as a kit you must solder it yourself. (There are two exceptions of persons who helped me in the development).

Regards
Sascha

[1024MAK]

Mark

[1024MAK]

This is the way that I assemble ribbon cable type IDC connectors:-
First I cut two pieces of softwood to size. I then sandwich the IDC connector between the two pieces of wood.
This sandwich is then put in between the jaws of a vice. I then carefully use the handle of the vice to close the connector until the "V" pins do their job and "bite" in to the ribbon cable, and the plastic clips snap in to place

Mark

[sirmorris]

For IDC connectors which have pins for direct connection to PCBs I do the same except I put 2 layers of stripboard over the pins so that they don't get damaged when I squeeze 'em...