Memory problems with ZX Uno.

Dudas, cuestiones, sugerencias y peticiones en general sobre el proyecto / Questions and requests about the project
redhawk668
Mensajes: 5
Registrado: 06 Abr 2018, 14:48

Memory problems with ZX Uno.

Mensajepor redhawk668 » 14 May 2018, 23:05

Hello There,

I've built a ZX Uno 4.1 from scratch and at the first test the FPGA was found and I could program the SPI flash and run some cores on it. So far so good, the problem is with the memory. I have soldered a IDT SRAM chip, type 71V424S10PHG. When powering up my ZX Uno it says 512K Ok, when testing it in bios no problems found and running the testcore all tests have good result, no errors found.

When running cores on it, for instance the Spectrum core with a 128K ROM, I get memory failures and when running demos or games for 128K Spectrum it sometimes reset or I get a complete crash. Other cores have memory issues too.I am running Bios version 0.72 and the latest Spectrum core. I've tested the memory with ZX-Diagnostics by Brendan Alford, when testing 48K, it passes all the tests. When testing 128K, all banks fail except bank 4.

What could be wrong?

Avatar de Usuario
jotego
Mensajes: 138
Registrado: 11 May 2016, 23:45
Ubicación: Valencia
Contactar:

Re: Memory problems with ZX Uno.

Mensajepor jotego » 15 May 2018, 00:00

Lo obvio es que pruebes las soldaduras. Repasa que estén todas bien.

También puede pasar que el chip de memoria se haya calentado mucho cuando lo soldaste y esté un poco roto.

Avatar de Usuario
antoniovillena
Mensajes: 2545
Registrado: 27 Sep 2015, 20:41

Re: Memory problems with ZX Uno.

Mensajepor antoniovillena » 15 May 2018, 00:07

This SRAM IC is not tested with the cores. Theorically it has the same speed, 10ns, but probably has different timings than Alliance or ISSI chips we have, and for this reason fails when 128K timings are selected in the Spectrum core. If doesn't work resoldering the pins, try with an older CORE like T24 or EXP25. They are less aggresive with timings.
http://antoniovillena.es
http://retrolandia.net
ZX-Uno · Clon de ordenador ZX Spectrum basado en FPGA

redhawk668
Mensajes: 5
Registrado: 06 Abr 2018, 14:48

Re: Memory problems with ZX Uno.

Mensajepor redhawk668 » 15 May 2018, 10:18

I have ordered some ISSI 512KB SRAM chips, so I'm going to replace the IDT chip. I've tested the T24 core and it has even worse results, so I guess the IDT chip is not quite compatible with the ZX Uno. The ones I've ordered are IS61L5128AL-10TLI, so that means 512KBx8, 10ns and 3,3 volt supply voltage. I think this will solve the problem and I can enjoy my self built ZX Uno :D

redhawk668
Mensajes: 5
Registrado: 06 Abr 2018, 14:48

Re: Memory problems with ZX Uno.

Mensajepor redhawk668 » 21 May 2018, 01:38

My ZX Uno is working 100% now, thanks for the help. I’ve replaced the IDT SRAM with an ISSI SRAM.


Volver a “Preguntas y peticiones / Questions and requests”

¿Quién está conectado?

Usuarios navegando por este Foro: No hay usuarios registrados visitando el Foro y 1 invitado