Please try [8bit4ever SX-1] + [GR8NET]

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Par thalin

Rookie (23)

Portrait de thalin

20-10-2018, 21:24

When I start the SX-1 with GR8NET it locks and there is no video output. However if I then push the reset button I'm able to start it successfully. This happens regardless of dip switch configuration.

Have anyone tried this? I'm also interesting to know if this happens with Zemmix Neo + GR8NET.

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Par Pencioner

Scribe (1335)

Portrait de Pencioner

22-10-2018, 00:11

There's no problem with GR8NET and Zemmix Neo - works flawlessly even with the Turbo modes

PS Do you insert cart into onboard cartridge slots or use the external (adapter) slots?

Par Grauw

Ascended (9584)

Portrait de Grauw

22-10-2018, 00:28

Is the power supply strong enough? Both have FPGAs that need to initialise on a cold boot and maybe they draw more power during that time.

Par thalin

Rookie (23)

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22-10-2018, 13:44

I have tried both the internal and external slots. It did not make any difference.

It should be strong enough. But to be sure I have tried with a bench supply that have more than enough power.

Par Eugeny_Brychkov

Paragon (1172)

Portrait de Eugeny_Brychkov

22-10-2018, 15:59

thalin wrote:

However if I then push the reset button I'm able to start it successfully.

Sound like reset signal problem. Is there circuit diagram availble for the SX-1 device? I wonder what is going on the reset signal when SX-1's FPGA is configuring and just after it - is there a pull up or down resistor on the line? What is the active low duration? Unfortubately can properly only be seen with the scope...

I do not remember I've seen specification about reset signal duration in the MSX standard, however it must be present in the documentation (at least for completeness).

Update: I did small research on the SX-1. There's no tech information available apart from pics on the internet (one from 8bits4ever website and another from MRC thread):

First, I see difference in the silkscreen, thus there must be several versions of the device. Then, looking at the board pic, I see it uses same reset supervisor M51953 as OCM. The one major difference I see it uses buck converter LM2596. Its fequency is 150 kHz which is relatively low. It features non-ceramic caps (aluminium or tantalum) of relatively high value requiring low ESR. Low ESR tantalum are relatively expensive, thus I see aluminium are used. Not clear if layout follows layout guidelines (see the datasheet), IMHO inductor is too far away from the device. Seems copper tracks on the board are slightly narrow and of wrong shape (to say the least). They most probably withstand current, but narrower tracks are subject to the noise and cross-talk.

For further reading:, and, it is very important where the components - in particular capacitors, were sourced.

No information about power supply requirements on the main page. Which power supply is used? Is it provided with the board?

I need more technical info on the device to make complete analysis.

Par Alexey

Guardian (2989)

Portrait de Alexey

22-10-2018, 17:48

Certain MSX machines have a very short power-on cycle - below 130ms. This is the time after power on and the Reset signal going high, when the BIOS starts its code. A few cartridges, for example our Carnivore2 and (according to what I heard) MegaFlashROM need more time (190ms for Carnivore2) for the FPGA chips to read the firmware from configuration EEPROM and to fully initialize.

We have found the solution for this problem by pulling the Wait signal down until the FPGA is ready. Seems to work on all machines that we tried on. More info in this thread:

It's highly likely that the same problem happens with other complex hardware that is FPGA-based. Just a thought...

Par hamlet

Scribe (3444)

Portrait de hamlet

24-10-2018, 08:53

SX-1 and GR8bit works well for me. Got the green board one and a (very) cheap power supply.

Par Eugeny_Brychkov

Paragon (1172)

Portrait de Eugeny_Brychkov

24-10-2018, 09:22

hamlet wrote:

SX-1 and GR8bit

To be sure - you meant GR8NET?

Par hamlet

Scribe (3444)

Portrait de hamlet

24-10-2018, 09:29

Of course I meant GR8NET, GR8bit s waiting for its completion, hope to get it working this winter...

Par KdL

Paragon (1375)

Portrait de KdL

27-10-2018, 09:18

All Zemmix Neo firmware are compatible with SX-1 but I suggest to try the various layouts and/or firmware versions (it is equivalent to try the various Quartus II optimizations).
The power supply should have a dynamic range but I suggest DC 12V 1A with positive polarity.

Par 8bits4ever

Resident (46)

Portrait de 8bits4ever

27-10-2018, 21:54

We've tested most of the cartridges we produce (Carnivore2, SD-512, CF-640, FDC-600, FM-PAK, MSX Blaster) with the SX-1 board. We did not find any problems so far. Also tested some original ROM game carts, but nothing special with those. All test were made using a 9v DC (outputs 12v unconnected) center negative PSU. The unit can take up to 16v DC, but is best to keep the DC input between 9-12 volts.

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