Forthcoming Cambridge CfCH events: RetroComp.Sale Sun 26th Feb, RCF-Japan 1st&2nd Apr

[ortek_service]

Originally Posted by Mark1960

I have a CGL M5 which was a version of the Sord M5 sold in the UK. Also the G-Basic cartridge which was a big improvement over the version originally supplied and made it possible to create quite good animation of the sprites and audio. The G-Basic cartridge also added extra ram. I haven’t powered it up since moving to Canada due to the 240v power supply brick and concern about power supply timing for the dram if I try to make a replacement. I also still have a few cassette games and the cassette recorder which no longer works since my son fitted the batteries reversed, mechanics still work so one day I’ll see if I can get a replacement IC for this. I disassembled the M5 and removed the internal RFI shields but still have all the bits except the screws to hold it together.

When I initially saw that the M5 had BASIC F G & I, I assumed they were incremental enhanced versions, and they'd skipped H and A - D (which seemed a lot of versions to go through) But from looking at this: https://en.wikipedia.org/wiki/Sord_M5
I now see that G was better than original I, and you had to pay £35 more for it. Plus another £35 for BASIC-F, for Floating Point (that presumably didn't include Graphics & Sound of BASIC-G?). So if many had to have at least G and F to run all BASIC programs that could be written for it, that was another £70 on top of the £195 base price.

With Only 20K of base RAM, of which 16K was used for Video, then I cam see why there were few games etc. for it on cassette, with only 4K left - Rather like VIC-20, which only had 3.5K out of 5KB total available, as standard, so many games were on ROM cartridge / you needed extra RAM cartridges.
There doesn't seem much info about expanding the M5's total RAM and whether this could only be done via cartridge-slot.

I'm a bit confused about comment of concern for a replacement Power supply's timing for the DRAM - As surely the PSU outputs to main computer logic are all DC, and they don't use mains-frequency for any timing ? (unlike mains-powered digital clocks)

Co-incidentally, I note that the M5 used the TMS9918, mentioned earlier.
As well as the same Texas Instruments SN76489 Sound IC, used by the Beeb.
So with (Zilog?) Z80A, that was quite a few IC's from USA IC companies, for a Japanese-designed computer (Although maybe like MSX1's)

[TonyDuell]

I suspect the comment about powr supply timing for the DRAM relates to the 3-rail DRAMs like the 4116. You had to ensure the -5V Vbb supply was present before the +12V supply and that the -5V supply was removed after the 12V supply. Otherwise it was like running an output valve with no bias, the chip got hot and bothered.

I've never seen a comptuer that did this by any other way than choice of smoothing capacitor values and the like.

[TonyDuell]

I suspect the comment about powr supply timing for the DRAM relates to the 3-rail DRAMs like the 4116. You had to ensure the -5V Vbb supply was present before the +12V supply and that the -5V supply was removed after the 12V supply. Otherwise it was like running an output valve with no bias, the chip got hot and bothered.

I've never seen a comptuer that did this by any other way than choice of smoothing capacitor values and the like.

[Mark1960]

The TMS99xx uses the 4116 dram which has separate input and output for data. The TMS99xx has the data output shared with multiplexed address output and a separate data input port. I guess this might have been a slight saving on silicon for output drivers and avoided the need for tristate output on the data to ram.

The TMS91xx uses the 4416 dram, 5v only, which has shared data input and output, so the TMS91xx has a bidirectional data port and the interface timing is slightly different. They are also easily used on the later 4464 dram leaving one address line grounded so only 16k available to the vdp. The 4464 might be easier to source as its a little more recent than the 4416.

Other than the dram interface I don’t think there are any improvements in the TMS91xx.

[Mark1960]

Originally Posted by TonyDuell

I suspect the comment about powr supply timing for the DRAM relates to the 3-rail DRAMs like the 4116. You had to ensure the -5V Vbb supply was present before the +12V supply and that the -5V supply was removed after the 12V supply. Otherwise it was like running an output valve with no bias, the chip got hot and bothered.

I've never seen a comptuer that did this by any other way than choice of smoothing capacitor values and the like.

Thats right, I could easily connect three wall warts to get the three voltages, but I’d need some way to sequence the voltages and that might not be so simple.

[ortek_service]

Originally Posted by Mark1960

Thats right, I could easily connect three wall warts to get the three voltages, but I’d need some way to sequence the voltages and that might not be so simple.

Thanks for info - I now understand it is the sequencing of the various DC-rails, that was a concern.

Presumably, you could just step the mains voltage with a 115 to 230Vac (auto)transformer etc. as wouldn't have to be that high-powered and step-down ones have often been used here (IIRC Tandy / Radio-shack sold them) for use with fairly-low power equipment designed for 115Vac supplies only, with no internal multiple transformer primaries that could be re-configured. (I presume the CGL M5 PSU only has a single primary?)
And a friend used one with a Taylor Valve Tester he gopt cheap, due to it being 115Vac.
- Although I'm not sure how common step-up ones are over there, and if there may be more safety concerns about the higher-voltage output that might restrict sale of these (but could fairly-easy DIY one, from a twin-primary 0-115Vac etc. transformer)
There was sometimes concern about running transformers 'designed for 60Hz operation', at 50Hz. But I imagine maybe less, the other way.

[Mark1960]

The transformer in the power brick only has a single primary I think, its quite a while since I looked. Either that or I wasn’t sure which way to pair them together.

We have 230v available via special connectors for electric cookers and washing machines. These are two opposite phases of 115v relative to neutral, though not sure if neutral is available in the connector. I’ve just been a bit wary of connecting uk appliances designed for neutral at close to earth potential.

[ortek_service]

Yes, I'd overlooked (used to be for fixed-wired?) high-power appliances 230Vac supply over there. Although I'm not sure how widely distributed the 2-phase are for this, and if only in basements / kitchens etc. so may not be conveniently-located for general use.
Commercial premises over here sometimes had all three (120deg apart) 230V phases, distributed all around larger buildings, to more-evenly balance the load. But you had to ensure that sockets within the same room etc. weren't on different phases, for safety. And residential premises were also wired in sequence on the three phases.

If the PSU is just a double-isolated plastic-cased one, with no Earth wire, and with the mains-lead wires going straight into transformer then there shouldn't be an issue with connecting that to it - Some of this type often had Fig.8 zip-wire mains-leads, with no polarity marking - as mains-transformer primaries are naturally balanced and not important which side is more live than other relative to earthed or floating core. It does look quite a large PSU, from one in this picture: https://en.wikipedia.org/wiki/Sord_M...File:CGLM5.jpg

A mains-switch in nominal Live / Line side, may complicate matters a bit - Although I've seen quite a few US-origin equipment where they put the mains switch in one side and the fuse in the other, which was deemed rather unsafe-practice on UK's unbalanced supply as you could literally get a full-mains voltage shock if you thought it was switched-off / fuse had blown, whilst working inside it.

[TonyDuell]

You can easily get 110V to 230V step-up transformers in the UK, and they're not ridiculously expensive. I am not sure about finding them in the States though.

I have never come across a power supply in a 'small' computer where the transformer is critical for the power sequencing. If you know what the secondary winding voltages of the the transformer in the power brick are, then you could replace it with a similar transformer with a 115V primary widing.

[ortek_service]

Originally Posted by ortek_service

I've recently found out about these events being held there (often hidden in their half-term special-events email update I get), that may be of interest

http://www.computinghistory.org.uk/d...February-2023/

Sellers just pay £10 for a table. And it just says buyers pay on door, and get museum admission with no advance-booking for this event - So I presume that's actually the same current £10 admission price (although £8 for over-60's) for most people!

>>
>>

And they are also doing a Japanese systems weekend event, in April: http://www.computinghistory.org.uk/d...nd-april-2023/
- I presume it's not just Games consoles, but earlier Sord / Sharp / Tatung Einstein + various MSX etc home-computers.

Bump - Unfortunately I didn't make the Retro Computer sale, back in Feb, but would be interested to see any photos / reports of what it was like, in case they hold another (And might even be tempted to have a stall).

But a reminder of the Japanese-systems event this weekend, and I wondered if anyone else on here is planning to go?
- I'll hopefully be going there (Probably for Sunday afternoon), to see what's there.
The CfCH event page: http://www.computinghistory.org.uk/d...nd-april-2023/ has been updated / has details of who t contact, if you want to exhibit anything, and currently has these Confirmed Exhibitors (I see Timbucus, at last year's RCF, is due to be there again) - I presume most for both days?:

Asobi.tech
@asobitech
Quang has pretty much every Japanese console ever released and will be bringing a selection of the rarer and more unusual machines to show us!

Adrian Page-Mitchell
When he's not looking after the collection here at the museum, Adrian's busy polishing his own collection of PC Engines and other Japanese consoles. He'll be bringing PC Engines, Tomys, and maybe even some NEO GEOs!

Tony Jewell
@HereBeDragons3
The Dragon 32 might not come from Japan, but plenty of other machines in Tony's collection do...!

Dan Wilkin
Resident Japanese train enthusiast Dan will be bringing along a selection of games and hardware from the hit arcade train simulation Densha de GO!

John Newcombe
@GlassTTY
John will be displaying a selection of Japanese pocket computers from Sharp, Casio, and Seiko. In addition, the Epson HX20, probably the worlds first laptop computer, will be presented as never seen before.

John Brown
@jcrowly
Some Japanese consoles are known through out the whole world, others are not. Come see a few of those lesser known consoles, some of which are probably not well know for very very good reasons.

Phil Searle
Phil will be raiding his collection of Sega systems to bring us a great selection of computers and consoles.

Adrian Graham
@binarydinosaurs
Adrian will be hoping to avoid a hernia as the lugs his huge Sanyo and Sharp systems (complete with printer) to the museum, where we have a reinforced table waiting for him!

Roy Templeman
@loudscotsbloke
Roy will be bringing a collection of oddballs and underdogs from the world of Japanese micros.

Tim Gilberts
@timbucus
Tim will demonstrate the world of Japan business computing with his Sanyo MBC555 and Epson printer.

[ChrisOddy]

On a similar theme Owen and I are planning on attending the forthcoming 'Econet Party' at The National Museum of Computing Bletchley on the 20/21st May.
I guess its a bit modern for this forum - I will be taking my collection of early Acorn machines along but might sneak the odd MK14 and related project in !

[Timbucus]

Yes I will be there both days and I think all the others - no MK14 sorry as it is strictly a historical business exhibit from me although the SAGE accounts do contain records of various computers and addons bought in 1985 by Gilsoft.

Well the MK14 has a place at ECONET as its EPROM programmer was used to burn the first system 1 PROM...

[ortek_service]

Originally Posted by Timbucus

Yes I will be there both days and I think all the others - no MK14 sorry as it is strictly a historical business exhibit from me although the SAGE accounts do contain records of various computers and addons bought in 1985 by Gilsoft.

Well the MK14 has a place at ECONET as its EPROM programmer was used to burn the first system 1 PROM...

Hopefully, I'll see you again there again.

Yes, there's quite a bit of shared heritage between Acorn and SoC, with the System 1 kind of being an MK14 with a different processor (Plus Acorn did eventually release a PROM-Programmer for their system). And when Chris Curry had apparently wanted to move to a 'better' uP, but Sir Clive didn't, it ended-up with Chris Curry leaving to co-found Acorn.
(Of course, it wasn't long before SoC / Sinclair, moved onto the Z80 and maybe the start of the 6502 vs Z80 battles in the UK)

I don't think Acorn Econet / Computers are too modern for this forum, as although it's a 'Vintage Computers' area, that's probably relatively much more recent than how vintage cars etc. are defined. So I would guess anything that's 1980's or earlier / mostly non PC-compatibles, would qualify - even if most of these are commonly called Retro Computers.

But with other quite-active sites for Acorn (Stardot) & Nascom (on Groups.io) etc. then maybe this area is more for those computers that don't have their own dedicated website group / aren't often discussed on other purely retro / vintage computers forum websites.

[ortek_service]

Originally Posted by Timbucus

Yes I will be there both days and I think all the others - no MK14 sorry as it is strictly a historical business exhibit from me although the SAGE accounts do contain records of various computers and addons bought in 1985 by Gilsoft.
>>

Good to talk to you at this event, earlier today, and see your Sanyo 'x86/88 early semi PC-compatible' computer - including last minute addition of a colour monitor, it hadn't come-with, but did output colour-video without the large high-resolution graphics board that one of the Binary Dinosaurs ones had.

BTW, this was the 'Computing Today' issue I saw in their 'late 70's /early 80's Office', that had a cheap 'printer' (actually surplus GP Teletype) project feature: http://flaxcottage.com/ComputingToday/7911.pdf


Surprisingly, I didn't see any MK14's there today- apart from a picture of one on the 1977-year SoC/Sinclair anniversary themed posters they had.

But maybe some things had been swapped-around, as most of the Sinclair exhibits were in the foyer area, with the main hall having lots of new 'Made In Japan' labelled-on-details computers (several early 80's still using 8" FDD's) & consoles additions (maybe more-permanent than some of the ones people had brought to show in there just for this event).
- Many of which I'd never heard the models (& some makes) before. As well as Japanese-only? market versions of USA companies products like Atari (2800) VCS + Commodore.

[ortek_service]

If anyone else picked-up a free Dowty MODEM from this event, that Timbucus offered me a couple and said someone had brought a box of 20 of these with them, then co-incidentally I've just found someone else recently enquiring about these on Stardot: https://stardot.org.uk/forums/viewto...?f=66&p=387560

Where they provided some useful links to a website: https://www.casecomms.com/product-ov...managed-modem/
- that has specifications, plus downloads of pdf data sheet and Reference Manual (Have to 'Register' to download that, but details don't require verification, so can enter anything to create a one-off account for this) - Or to save the trouble, I've attached these.

Inside these (2400bps max V.21,V.22,V.22bis,V.23, V.42(bis) error correction / data compression) MODEM's is an 80C188 (PLCC-socketed), and a number of 0.6" wide turned-pin socketed IC's: TMS27C010-20 EPROM, 2x KM62256ALP-10 SRAM's, uPD71055C, uPD71051C, Z85C30-8PC/A, Rockwell 10464-20, and a soldered-in C5308-15 in 'ZigZag DIL' package. As well as a Varta Lithium 3V 1/2AA battery (No signs of leakage from this type, well past 10yr shelf-life, at least).

[Timbucus]

Indeed it was great to catch up IRL - it is always a risk going to meetups like this that you come home with more than you took... I did this time and am still 'reeling' from my decision.

[Phil__G]

Is there a 2023 date yet for the actual 'Retrofest', I thoroughly enjoyed last year (my first) but I dont see it listed on their events page... only the swapmeet?
Ta v much
Phil

[Timbucus]

Originally Posted by Phil__G

Is there a 2023 date yet for the actual 'Retrofest', I thoroughly enjoyed last year (my first) but I dont see it listed on their events page... only the swapmeet?
Ta v much
Phil

This will be 4th/5th November again - it should be going up on the page soon.

[Phil__G]

Thanks Tim, I can do November

[ortek_service]

Thanks for the advance info on this years's RCF. I'll try and go again, as I've been to the previous two.

I've just discovered, from this Computer Conservation Society Webpage https://www.computerconservationsociety.org/ (See attched poster, I saved from there) another 'Autumn Computing Fair' Vintage / Retro event that might be of interest
- Although organised by the BCS, and at the (not too far away from CfCH) University of Hertfordshire.
It says stalls are free, but not sure of costs for visitors / if event is free for BCS-members (Although I'm only an IET member, not in BCS as well).