Retrocosm – Vintage & Retro Computing Blog

Random mutterings on retro computing, old technology, some new, plus any other stuff that interests me

@retrochallenge – Under The Hood


Another string in the bow of the MTX 512’s beautifully designed case is the ease of access it offers to the machine’s internals.  Three screws hold the endplates of the case in place, remove these and the top swings up rather like a car bonnet.  Disconnect the keyboard cable and remove one further screw on the bottom of the case and the mainboard slides out with ease.


Endplate Removal

On opening my non-functioning 512 I was presented with a bit of a horror story, clearly someone none too skilled with a soldering iron had made several attempts at repair in a number of areas.  Still, it would be rather churlish of me to complain too much given my own inexperience with soldering.

The first thing you tend to notice when you open up the machine is the prominent electrolytic capacitors on the right of the board.  Unlike most machines of the era, the external power supply for the MTX is a simple transformer, voltage regulation is taken carry of in the machine itself.


Disconnected Capacitor And Other Damage

On close inspection I noticed the fast blow fuse on the board was blown, of the two large electrolytic capacitors, one radial and one axial, the latter was actually disconnected from the board at one end.  There was a fair amount of evidence of poor soldering including some melting to the rear case plastics.

New to the Memotech I enquired at the Memorum forum as to what the best course of action would be.  Everyone there was very helpful and Mark gave me a detailed run down of how to put a meter on the voltage regulators and check for the correct readings.


RF Signal From Working Memotech

I ordered a couple of suitable new capacitors and replaced the originals.  This was relatively straightforward and given my lack of soldering skills completed with much relief without causing any further damage.

On reassembly the machine is still not putting out any video via the composite connection.  There appears to be something coming from the RF output as I can almost tune in to it without quite locking on to the signal, something I can do with the same television and my other working machine.

To be fair however even the soldering on the connections to the video outputs looks suspect so the next task is to unplug the backplate and try the known working one in its place.

@retrochallenge – Memotech MTX 512 Introduction

Memotech MTX512

During the home computing boom of the early eighties a number of innovative British companies were entering the burgeoning market with an eclectic mix of machines and hardware.  Whilst the Sinclair Spectrum and Commodore 64 battled it out for top honours, other less popular but often no less and in some cases more capable machines were finding their way into the bedrooms of the nation’s (mostly male) youth.  Orics, Electrons, BBCs, Dragons, Newbrains and Jupiter Aces to name a few, were to leave the consumer with a bewildering choice of hardware and go on to engender tribal loyalty upon purchase.


Anodised Aluminium Case

With their sleek, seductive styling the Memotech MTX range of machines were, along with the Atari 800XL, arguably the most aesthetically pleasing computers of the era.  In an act of unwitting prescience the designers eschewed the typical beige plastics so popular at the time for an altogether more substantial anodised aluminium case.  Thus unlike many of their contemporaries which have over the years succumbed to awful yellowing from leached flame retardant in their plastics, MTX machines emerge from owner’s lofts looking much the same as they did the day they were packed away 20-30 years earlier.  It is perhaps no surprise that a metal case was favoured given that one of the co-founders of Memotech, Robert Branton was a metallurgist.


Expansion Socket

Branton, along with Geoff Boyd formed Memotech in Oxford in 1981 and originally rode the wave of the home computing boom by producing peripherals for the Sinclair ZX81.  However with the arrival of the Zx81’s successor, the Sinclair Spectrum they shifted gears and went on to design and produce their own computers, including the MTX range of machines.

Built around the ubiquitous Zilog Z80, specifically the Z80A running at 4 MHz, there were two initial MTX labelled machines, the 500 and 512 with 32k and 64k of RAM respectively (the 512 is expandable to 512k RAM, hence the name.)  Pitched at the higher end of the market and with similar abilities to Acorn’s BBC models the MTX machines featured in an impressive 32k of ROM some interesting additions to the industry standard BASIC such as a built-in assembler/disassember, debugger and Noddy, a method of programming the computer similar in many respects to Hypercard.


No problems with the FCC thanks to the metal case.

Graphics were provided by the T.I. TMS9918A with 16k of video RAM and capable of 16 colours at 256 x 192 resolution.  There was support for 32 user definable sprites.  Sound was four channel courtesy of another Texas Instruments chip. Plug in ROM cartridges were also available as was the reassuringly large and expensive FDX unit which added floppy and or fixed disks and support for CP/M.  Without the latter programs were loaded and saved to tape via standard mic/ear sockets.  RS232 communications were available via a plug-in card but were not fitted as standard. On release the 500 retailed for around £275 whilst the 512 typically sold for £315.

From my own perspective I currently own two Memotech MTX 512s.  One is in fully working condition, the other is currently dead.  For this year’s Retrochallenge my intention is to familiarise myself with the machines, see if there is any prospect of resuscitating the dead unit and hopefully play some games and take a closer look at Noddy.

There are some excellent resources covering Memotech computers, here are a few that I’ve used and recommend:-

A superb Memotech article on The Register.

Dave’s excellent Memotech MTX resource.

Another great Memotech site.

Memotech Forum

Mac Pro 1,1 And Mavericks


Back in 2012 I made a numer of upgrades to my Mac Pro to try to extend its useful life.  The upgrades were a success and the posts I made such as upgrading the Xeon CPUs remain some of this blog’s most popular.  It therefore seems likely that I’m not alone in still running one of these venerable machines.

After what seems like an eternity waiting for the new Mac Pro to arrive, as superb as it is it doesn’t suit my needs.  After factoring in the costs of adding Thunderbolt equipped external storage it is also impossible to justify the cost.  From a performance perspective I’m still not suffering any great hardship with my Mac Pro 1,1.  However I have a number of other Macs and have become accustomed to running OS X Mavericks and would really like to be able to run it on the 1,1.

The last version of OS X officially supported for the Mac Pro 1,1 is 10.7.5 Lion.  Later versions require a 64bit EFI to boot.  My Pro is the very first of the Intel machines introduced and is crippled by a 32bit EFI although the Xeon CPUs are of course 64 bit.  A number of hacks have been in the wild for some time and allow you to get around this limitation.  The most common I’ve seen being running the Chameleon boot loader from a separate drive using legacy boot, Jabbawok created a guide.


Useful Increase Under Mavericks

Recently it has become possible, thanks to the excellent work of Tiamo over on the Mac Rumours forum to install Mavericks on the 1,1 without the need for Legacy Boot and additional drives.  I actually took an alternative route to get Mavericks on to my 1,1 but still required Tiamo’s rewritten boot.efi.

Some months ago I managed to install a later, unsupported version of OS X onto both my iMac G4 and Cube.  This was achieved by launching the machines in Target Disk Mode (TDM), attaching them via Firewire to my Mac Mini G4 and running the installation from there.

I decided therefore to attempt the same trick with the Mac Pro.  I removed all other drives and inserted a new Crucial M500 SSD, booted the machine into TDM and attached it via Firewire to my Mavericks friendly 2010 iMac.   I ran the Mavericks installation via the iMac and after initialising the new SSD installed the OS.  When the installation had finished and before rebooting I used the iMac to overwrite the boot.efi in the following two locations on the new drive with Tiamo’s modified version.



I find the easiest way to find these directories is to launch terminal and enter ‘open -a finder /volumes/volumename/usr/standalone/i386′ where ‘volumename’ is the name of the disk on which you’ve just installed Mavericks and ‘open -a finder /volumes/volumename/system/library/coreservices’.  This will launch Finder windows with the correct directories, you can then drag the boot.efi in to place.


Velocity Solo PCI Card

Afterall you don’t want to accidentally overwrite the boot.efi on the machine you’re using to run the installation.  Upon reboot the Mac Pro dutifully launched OS X Mavericks, success!  After setting everything up I now have full iCloud and Internet Accounts integration with Twitter, Facebook and so on all working with the Notification Centre.  As yet I have not experienced any problems.  I do wonder whether any future updates from Apple may wreck things, time will tell.

One easy to resolve problem this process had left me with was that I had to remove a drive to accommodate the new SSD.  I wanted to keep my previous Lion installation intact so I could boot into it when required.  The drive I therefore removed contains my Windows 7 64 Bit installation which itself had involved a fair amount of jiggery pokery to get running and still gets used regularly.


SSD Attached And Ready To Install

With all my drive bays full, I have a 4tb RAID occupying the last two slots, I decided to order a Velocity Solo PCI card from Apricorn.  This card will hold a single SSD and support booting from the drive.

Installation was very straightforward, simply attach the SSD and slot into a spare PCI bay and you’re good to go.  You also get an additional SATA connector on the card which may come in handy.

Everything is working very well at the moment, I even saw an improvement in my Geekbench score under Mavericks, an additional 400 points or so.  The machine definitely feels snappier under Mavericks so hopefully, barring hardware failures, another couple of years out of this extraordinary machine.

Update:- An interesting footnote, running Geekbench simultaneously under Mavericks and Windows 7 via Parallels yields multi-core results of 7555 and 3905 respectively.

Update (24/02/2014):- Updating to OS X 10.9.2 will overwrite your boot.efi files and prevent your installation from booting.  The new boot.efi file in the coreservices folder is locked and tricky to remove or overwrite.  To get around this simply reboot again in target disk mode and copy the boot.efi over from another machine.

Update (27/05/2014):- Have updated to 10.9.3 with no apparent problems.  It appears there is no need to restore the boot.efi after this update as it is not overwritten.

Update (15/07/2014):- Updated to 10.9.4 with no apparent problems.


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