Tatung Computer Forum

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm Reversing the price question, how much would people be willing to pay? Let's use £50 price bands: £0-50, £50-100, £100-150, etc.

Speculator will cost more than Silicon Disc (Spec and SD for short) due to scarcity. I need to buy eight 256Kb*1 DRAMs per SD. Best price in UK I've seen is £1 each. Please tell me if you know of cheaper reliable source.

Hmm well it's difficult to say, depends if you're just selling boards, kits or fully assembled and your time to put it all together. I guess it's just what you're comfortable with.

£1 seems reasonable for the DRAMs.

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm Re Spec, times have changed since the 1980s. Supporting only a few games, loaded from tape, is no good now. I'm thinking of loading files from laptop/PC via RS232 at 9600 baud (files not supplied by me). Does anyone use a USB to RS232 cable with Einstein-compatible connect? This could be included with Spec if needed. The Spec software would be simpler with RS232 loading. If I do this, is cassette circuitry on Spec board still wanted? It's not expensive, just fiddly to solder. One faulty Spec board works fine apart from cassette input.

An RS232 enhancement would be a neat addition but I'd still want a cassette input - it's all about the novelty Personally i'd be ok with a faulty one, interesting exercise to fix!

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm Another cost is 60-way ribbon cable and IDC sockets. I have about 20 spare most of which probably don't work. I might be able to cut off connectors, undo them and crimp again. I don't have proper tool for this but I might have a small vice somewhere.

These parts are available from Farnell, I use a vice with plastic jaws in the absence of a proper tool. I've reused them before but it's a pain when the clips snap in the process.

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm Re BOM, both devices require two programmable logic (PAL) chips. I have some spares already programmed, not sure of numbers. I'd need to buy more PALs or probably GALs when these run out. The PALs mean it's probably best for me to assemble the boards although I could supply PALs if people want to do it themselves. SD has solder-resist but Spec does not, which I regret.

Personally I can program GAL/PALs as long as there's a JEDEC file available. I generally have to get GALs from China (Aliexpress) at about a 1/10 failure rate.

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm SD needs a ROM that goes in empty socket on motherboard. Again not sure how many I have. SD is drive 3: by default. A tiny .COM file I wrote can change logical drive numbers so that SD is 0: and system is reloaded from SD not diskette when progs end. Improves performance and overall SD makes huge difference to usability of the Einstein.

What sort of Eprom? I have a small stock of various types and can burn them. Again China is the easiest source but at risk of fakes.

Tony Brewer wrote: ↑Thu Sep 29, 2022 1:30 pm Are new 3" diskettes still available?

Sadly not, many of us myself included are using a GOTEK USB drive emulator so a disk image is fine.

I'm new to the Einstein so my question is, given that I'm going to fit a Gotek to my machine is there any benefit to having an SD fitted too?

I could offer a serial loading upgrade to everyone who already has the Speculator, when it's working.

Is there any other RAM drive option for Einstein apart from my Silicon Disc?

Tony Brewer wrote: ↑Thu Sep 29, 2022 7:57 pm I could offer a serial loading upgrade to everyone who already has the Speculator, when it's working.

Is there any other RAM drive option for Einstein apart from my Silicon Disc?

Not that I’m aware of

Another Einstein device I've designed is a micro SD card interface that connects to the user port. No PCBs ever made but hardware-wise it's trivial.

Tony Brewer wrote: ↑Fri Sep 30, 2022 12:22 pm Another Einstein device I've designed is a micro SD card interface that connects to the user port. No PCBs ever made but hardware-wise it's trivial.

This is very interesting, maybe I won't need a gotek if I get one of these.

Yes that would be a neat add on!!

Tony Brewer wrote: ↑Fri Sep 30, 2022 12:22 pm Another Einstein device I've designed is a micro SD card interface that connects to the user port. No PCBs ever made but hardware-wise it's trivial.

This sounds useful...however I still marvel at the quality of my Einstein's drives and discs. I acquired mine from a gentleman who had bought it in 1984 and used it to run his business until he retired some 25 years later. It came with a large collection of discs, all of which still work as do both drives!

Therefore, as useful as an SD card reader would be - I have one for my Spectrum, C64 & Amiga - my discs are still fit for purpose.

Preppie wrote: ↑Fri Sep 30, 2022 1:07 pm

Tony Brewer wrote: ↑Fri Sep 30, 2022 12:22 pm Another Einstein device I've designed is a micro SD card interface that connects to the user port. No PCBs ever made but hardware-wise it's trivial.

This is very interesting, maybe I won't need a gotek if I get one of these.

Yes, it could replace a Gotek probably. Think of it as a removable hard drive (or drives, e.g. 2 x 8MB). However, data transfer rate not stellar, ~12KBps max for reading, a bit quicker for writing. I could add uSD firmware to my silicon disc ROM.

A very warm welcome to the Forum, Tony.

Please add me to the list for both Speculator and Silicon Disc. Happy to pay whatever it costs for parts and your labour.

Fascinated reading about how the Silicon Disc operates. I see it defaults to Drive 3 under MOS.

"The silicon disc ROM patches the following MOS MCAL routines, so
that the silicon disc may be accessed as drive 3.

Number (Name - Description)

A2H (ZRSECT - 512-byte sector read)
A3H (ZWSECT - 512-byte sector write)
A4H (ZRBLK - Block 512-byte sector read)
A5H (ZWBLK - Block 512-byte sector write)
B6H (ZSLDSC - Select disc drive DOS)
BAH (ZRD128 - 128-byte sector read DOS)
BBH (ZWR128 - 128-byte sector write DOS)"

Very impressed to see that you've implemented drive mapping so the Silicon Disc can be configured as Drive 0.

"Provision has been made in the silicon disc ROM for logical (DOS)
disc drive to physical (MOS) disc drive mapping. The routine that
accomplishes this is the patched DOS drive select routine ZSLDSC.
This routine uses a special silicon disc variable at address
FDFFH to determine which physical drive corresponds to which
logical drive. This variable is interpreted in the following way

Bits 0,1 give physical drive number for logical drive 0
Bits 2,3 give physical drive number for logical drive 1
Bits 4,5 give physical drive number for logical drive 2
Bits 6,7 give physical drive number for logical drive 3

The default value is E4H or 11100100B, which gives a logical-to-
physical mapping of 0-0, 1-1, 2-2 and 3-3.

The main reason for having disc drive mapping is so that the
silicon disc can be configured as drive 0 when using the DOS,
making programs which refer to drive 0 when loading, for example,
do so much more quickly."

I now use FlashFloppy with a Gotek as Drive 1 so don't suffer quite as badly from disc swapping as I did with only one drive, but the Silicon Disc will improve my setup considerably