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Interface 1 Rom Upgrade

Posted: Fri Aug 21, 2015 4:44 pm
by derek

I have an Interface 1 with a version 1 Shadow Rom, I would like to update it to Version 2.

Does anyone know where I could get a rom image of Interface 1 Version 2.

I read on Dataserve Retro site that there maybe a version 3 rom, was that ever released.

Re: Interface 1 Rom Upgrade

Posted: Sat Aug 22, 2015 2:02 am
by 1024MAK
There is a list of known ZX Spectrum ROMs here, but many are not available to download from there, including the IF1 ROMs.

If a version 3 was released, it is rare, as I have not seen any, or any copies of it.

This link is interesting. May I suggest you also go here and help out ;-)


Re: Interface 1 Rom Upgrade

Posted: Sat Aug 22, 2015 10:34 am
by derek
Hi Mark,

Thank you for the web links and information, solves most of the issues.

Looks like Interface 1 v3 Rom was not released.

I just need to find a suitable Eprom to update the v1 Rom code. The Interface 1 service manual suggest the ROM is:

Motorola SCH9288 OP or Teaxs TMS4764NLZA

Whether these chips are available is another matter, maybe an adapter board can be made to fit a 8K Eprom for the updated rom code.

Re: Interface 1 Rom Upgrade

Posted: Sat Aug 22, 2015 6:51 pm
by 1024MAK
2764 EPROM vs 4764 ROM.png
2764 EPROM vs 4764 ROM.png (123.84 KiB) Viewed 5626 times

Re: Interface 1 Rom Upgrade

Posted: Sun Aug 23, 2015 11:16 am
by derek
Hi Mark,

Thank you for the information with regards to the M2764 eprom.

According to the Texas Instruments TMS2564 datasheet (attached) is pin compatiable with the TMS 4764 ROM, with the exception of:

Pin 1: Vpp
Pin 2: CS1
Pin 27: CS2
Pin 28: Vcc

I was going burn Rom v2 into a TMS2564, with my HILO Systems All031 programmer and mount the TMS2564 in a socket with pins 1,2,27,28 not connected to the Interface 1 board.

But due to the height restriction of the expansion connector, where the ROM is paced on the PCB, the eprom would have to be solder to the Interface 1 board.

Do you thik this would work.

Re: Interface 1 Rom Upgrade

Posted: Sun Aug 23, 2015 11:37 am
by 1024MAK
It may. But keep in mind that a 4764 ROM has pin 20 mask programmable and I know in the QL, the ROMs used positive logic for true (active high chip select). I don't know what the Interface 1 uses.

If no space for a socket, you will have to bend up the legs for pins 1,2,27,28.

Also, it may be an idea to ask some of the repair guys if they have a spare ROM.
So contact these people:
Dataserve Retro (yes, I know you already know about this site, keeping it for the benefit of others)
Mutant Caterpillar

Oh, and TMS2564 are a bit more tricky to get hold of, unless of course you already have one...


Re: Interface 1 Rom Upgrade

Posted: Mon Aug 24, 2015 9:43 pm
by derek
Hi Mark,

I put the IF1 rom in my All03a programmer and set the software to TMS2564 and rom was read into memory.

I have got 2 x TMS2564 eproms coming from Germany only £6 each.

Pity a static ram chip could not installed so custom rom images could loaded.

Re: Interface 1 Rom Upgrade

Posted: Thu Feb 25, 2016 10:07 pm
by Fruitcake
Perhaps a bit of a late contribution to the discussion but it you preferred not to modify your ZX Interface 1 then you could instead override its internal ROM with a version of the edition 2 ROM running from a ZXC4 ROM cartridge via a ZX Interface 2: ... _RS232.htm

Re: Interface 1 Rom Upgrade

Posted: Wed Apr 07, 2021 10:07 pm
by Erm
An even later contribution, but I've been playing with a few IF1's lately and have found that with 2 of them the ROM chips had failed. Very often it's the ULA that goes, but it seems the ROM chips can also die. Might be a coincidence but both were also the same type - TMS4764NL ZX84208 B8340L, made in Singapore (v2 versions from this manufacturer clearly state v2.0 on them and seem more reliable).

And this could be a useful tip too: I was attempting to read them with a Sinclair QL Eprom programmer, which supports 2564. It wouldn't read them, but did read half of it when I selected 2532, which is no good but it was a start. I solved the problem in the end by connecting a wire to pin 24 of the chip and then connecting that to where pin 28 would normally go to in the Eprom programmer socket. Both those pins are VCC on an actual 28 pin 2564, so the programmer must somehow check to see if those 2 pins are connected. I wonder if other Eprom programmers that support 2564's may also work with this mod.

With the extra connection I was able to read a few IF1 ROM chips absolutely fine, and in doing so was able to find 2 that wouldn't read at all, both from IF1's that didn't work. I replaced them with working ones and the IF1's then worked perfectly!

I haven't actually tried replacing an original ROM with a 2564 EPROM yet though, as it's just so fiddly and I had enough originals to go round (so far).