Sinclair ZX80 / ZX81 / Z88 Forums

Hi there,
some people already got some information about a new memory extension for the ZX81.
Here it is, called it ZXblast, that blows up the features of a ZX81 and let you have a blast with your old ZX81.

It may be used with the DIN 41617 connectors (64 pins a/c row like used in the german ZX team) or the standard expansion connector and has dimension of 100x80 mm or half size "europe board" (4.0 x 3.15 inches). In fact this is a cheap memory extension plus using USB flash memory/sticks for loading and saving data and offers SRAM and Flash ROM with either each 128k or 512kByte depending on what memory type is used. The business logic is inside a CPLD which allows to have several features like RAM banking, different ROM types and partly additional features the ZXmore offers (not all possible).

The USB ports may be used mainly for flash memory sticks but also additional hardware like joysticks or similar. I think there will be a cheaper starter version for people only need memory extension and loading/saving files and maybe bigger memory and more features for the power users with a bigger CPLD. This should be available around april or latest may this year. So just an announcement when you need a mass storage device with memory extension. Not 100% sure about pricing but the basic version should be in the range of about 25 GBP as self construction kit or 30 GBP ready to use (plug and play).

Looking good, Karl! If you need a beta tester...

Indeed looking good.

Out of interest what are you using to talk to the USB, I guess you have something on the bottom of the board?

Cheers,

Phill.

Can you make a short comparison between ZXblast and ZXpand?

The USB controller is on the bottom side of the board and already soldered, it's the FTDI VNC2 chip used on the ZXmore - this way I can use quite much code of ZXmore and shorten development time (software). I can not exactly compare it with the ZXpand because I do not know ZXpand very well and I do not know very well where the limits of ZXblast are exactly.

I am quite sure it will offer up to 56k RAM, load and save via USB and use of other ROMs than ZX81 (maybe up to 10 to choose from and easily to program when copied on a USB stick). There are some more options like banking RAM which mechanism is not yet defined. I think the main difference is to use USB flash media instead of SD cards and does allow other USB hardware as well as connecting a joystick, other keyboard depending on controller software/memory. I have to check out a few things but SD card is limited to storage only.

Some info on the ZXpand here (scroll down a bit) and here.

Mark

Okay - there is no AY support while the ZXpand also needs an additional AY module. So for sound you have to use an additional regular external AY module.

Some news about ZXblast - the boards are here and in the meanwhile I made a short test with programming it as plain 16k RAM extension and works as expected. So the CPLD programming has to be developed further for the other features and some software extracted from ZXmore to control the USB chip and some testing. Hopefully it will be available for sale in about 2 weeks now. Not too much work for it now necessary. Will have time for it next week.

Here are some pics:

And this is the completed board:

This is the backside.
Unfortunately, there is a small bug with 3 wires, crossing a pad.
Modified something and forgot to run design rule check again.

Here it is fixed with some bigger copper wires in orange colour, the final solution uses thinner copper wires in blue color which are not that prominent. The wires are soldered already when shipping the plain board and of course for completed memory packs.

This is great news