Compaq Deskpro 386s/20n: More Disk
So, the old beast is up and running once more. All is well, but I want a little more hard drive space. I've had a 256mb Transcend IDE "Disk on Module" lying around for a long time, so I've decided to install it into this machine.
The IDE connectors on these devices are reversed as they are actually meant to be installed directly into the motherboard. This Compaq does not have a standard IDE connector on the motherboard end, so I'll need a little bit of trickery to get this up and running. I'm going to call this device an SSD from here on; writing Disk-On-Module each time uses my shift key too much.
IDE Pinouts
What I'll try and describe below is where pin 1 is on either end of the cables and how the Transcend module doesn't mate correctly with the 'hard drive' end. For all intents and purposes, we're going to pretend that this Compaq Deskpro actually does have a standard IDE port on the motherboard end. We know it doesn't, but for demonstration purposes, let's stick to the IDE standard.
IDE cables are all female-to-female. Most of the time they have more than one female plug down the cable to allow both a master and a slave to be connected on one channel. The IDE cables in this Compaq are the original 40-pin type. These 40 wires are all connected straight through, down the cable and into the plugs. The drives then determine, via jumper settings, which is to be master and which is to be slave. In this scenario, we can take it for granted that this will occur and that we don't have to modify cables or plugs to allow selection of master/slave automatically.
The best way to explain the pin mapping is sideways. The diagram below shows pin one and two from the motherboard to the HDDs. The important part here is that mirroring occurs and that 1 and 2 seem to 'leapfrog' over each other on the way.
As you can see from above, if we plugged the SSD straight into the IDE cable IDC header then we'd have a mismatched alignment of pins. The top row of pins needs to be swapped to the bottom row. To do this, we either need to put an IDC header on the 'other side' (upside-down?) of the IDE cable, or create a new cable that'll swap the pins around for us.
Due to the staggering of the pins on the IDC header, it doesn't matter which way you orient the plug. The side of the cable is what matters. Then again, this isn't the total truth. If you were hooking up another hard disk, then the rotation definitely matters as the 'notch' must be facing upwards so that pin 1 is to the left (when looking at the 'hole' side.)
Confusing yet? The issue here is that everything is mirrored. Once you then add the rotation, it's a real mind-f##k moment. Either way, for this to work, we'll want to have a plug on the wrong side of the cable. Actually... is that what I really want to do?
You mean, ruin the Compaq IDE Cable?
The IDE cable in this Compaq is proprietary. The motherboard-end is an edge-connector onto the backplane and I can't imagine finding another cable like this, ever. Therefore, we're going to do as little damage as possible to add a slave drive. I could just slap the IDC connector onto the reverse-side of the cable cable, and this would actually minimise any work I had to do, but the issue is that I'd then have to leave a note in the machine to tell the next unsuspecting victim what I'd actually done. Unless you know what you're looking at, you won't have any idea that it's backwards and a normal disk wouldn't work.
Instead, I'll add an IDC connector the correct way, a little way down the cable, as per a standard slave connection. From here I'll then build an adaptor cable that will allow me to female-to-female plug in the SSD. Check the next diagram to understand this.
Note that the 'adaptor cable' seems to be miswired? Pin 1 is pointing to Pin 2!? This is perfectly fine, as that's the cables purpose in life. You couldn't do this with an actual device, but you can with a cable. In the end, if you follow the wires, you'll realise that we now have the pins lined up perfectly. We also have a magical space for the existing HDD!
Building the adaptor cable
After thinking about this for a while, I thought I'd google to see if anyone had done it before. Most people put IDE-CF cards in their ancient laptops, I've even tried to do this before. I then came across an article where Michael B. Brutman installs an SSD into an old IBM L40SX. It was great to see that my concerns of just plugging the 'SSD' into the IDE cable as-is was wrong and that the technique to build a cable was proven.
I went to the shops and bought the required components: ribbon cable and 3 40-pin IDC headers. I already had some rows of header pins available in the cache-o'-crap.
Constructing it was easy enough, just make sure that both your headers are facing up and, just for fun, align the notches the same way. We won't be caring about the notches... but do it anyway!
Now that we're done, we're going to hack the original Compaq cable slightly... let's put a header on the cable below the current header, allowing for a slave to be connected. Except that we're going to put the master here, using the old header at the end for our new drive. You can see from the shots below that the original cable had enough slack to allow us to fit the header in.
At this point, prior to plugging in the SSD, test the modification we've just done to the existing IDE cable! After this, the final trick is to just slap it all together. Make sure to set the SSD as the slave! I used the header pin rows, sliding the plastic down mid-way. I then found a power cable Y-Splitter and jammed it all into the case.
Configuring your new disk
Back to the BIOS, you'll need to select a size that is 'just-below' your SSD size. I found a 212mb that I was happy with.
This all worked like a charm. I was then at the usual DOS Prompt. FDISK indicated that I had a new fixed disk and allowed me to to switch to it by using menu option number 5. Doing so showed the old Linux partitions!
From there it was a quick partition deletion, creation and formatting session. All done in around 5 minutes. The result?
Oh File Manager, how I have missed thee.
Quadra 950: CPU/RAM Upgrades and Overclocking
When it comes to upgrades, the Quadra 950 has 16 SIMM RAM slots, 4 VRAM slots, a ROM SIMM slot, 5 Nubus slots and a PDS slot. RAM and CPU upgrades can be purchased via off-the-shelf means. Little is it known that you can also then overclock your CPU. Below lists some options for getting more horsepower out of your vintage Macintosh.
Apple PowerPC Upgrade Card
The previous owner already had the "Power Macintosh Card" Control Panel installed on the 7.6.1 system. After inserting the card, I went into the control panel and enabled the PPC Card. I was informed that a reboot was required and promptly did so. It rebooted.... Apple System Profiler indicated the same-old 68k processor? I had recalled online that one user had issues with the card, but then found that it wasn't seated properly. Trying this, I shut the machine down and then put the case on its side. A gentle downward press on the card from both top corners resulted in a rewarding click. Nothing sharp, but that feeling of success when you know something is now in the correct location.
I hit the power button and ... jeebuz.... what was that wretched chime? The 68k boot chime of the Quadra 950 is pleasant, if not downright triumphant. The chime that came from the PPC addon card was ... it sounded like a cheap knock-off MOD compared to an MP3. A dodgy, poorly-recorded sample. Either way... it worked. The screen then came on and I could actually see it drawing the background line-by-line as the grey pattern loaded. Then I saw it draw the MacOS central loading screen. I was running the Supermac Spectrum/24 PDQ+ at this point and that turned out to be the cause. It needs a software update. Meanwhile the onboard video performs much better.
Overall the UI seems much zippier with the PowerPC enabled. Placebo probably... I'll try and perform benchmarks once I have new HDDs and a fresh operating system. Maybe some more RAM too... In the meantime, here's some benchmarks done by Low end Mac.
I've read here at Apple Fool that you can actually remove the 68k CPU when running the PowerPC PDS card. Doing so also resolves graphics issues with other Quadra models. When overclocking (the only reason I found out that you could do this), removing the 68k CPU actually allows you to run the PPC upgrade at faster speeds!
Upgrade VRAM to 2mb
The Quadra 950 has 1mb of VRAM onboard. There are 4 slots in which 4 256kb SIMMs can be installed to extend the video memory to 2mb. This will allow 1152x870 @ 24-bit colour, which is comparable to any video card you can insert! Apple has a support page describing the options for each Macintosh model and you can see that the Quadra can only take 4 more SIMMs.
Four slots support 256k 80 ns VRAM SIMMs for a maximum total of as much as 2 MB of VRAM. 512k VRAM SIMMs can be installed, but four identical ones must be installed and the system can only use 256k of each SIMM.
ROM SIMM Slot
I initially thought that there was a cache slot next to the RAM slots on the logic board. If you look at the images below in the RAM upgrade topic, you'll see that, apart from the 16 SIMMs for system memory, there is another empty slot top-right. It's near the CPU, so cache made sense. It turns out it's a ROM SIMM slot, not a cache slot. In this slot you can put in a ROM that will override the on-board ROM.
Doug Brown makes ROM SIMM programmers that can write the SIMMs that'll fit into this slot. It doesn't seem that anyone, at all, on the internet has ever done this to a Quadra 950. I've been told that you can change the start-up tune and disable the memory check, if you want to... otherwise your options for profit from tinkering with the ROM are little. It would require some very low-level detailed hardware knowledge also!
But for fun, check out Doug's post where he changed his Macintosh IIci start-up tune to the Super Mario theme. If you do want to code ROM SIMMs, Doug has his ROM SIMM burner for sale here.
This slot does have me thinking... minimal OS on an 8mb chip... it'd be like loading from an SSD!
Cache Upgrades
Meanwhile, you can buy Nubus cards full of cache. These 'MicroMac Cache cards' come as PDS cards or 'slot-free', the latter being a device that is installed between your CPU and logic board. This piggy-back mechanism puts the cache right next to your CPU and keeps your PDS slot free for a PPC upgrade.
Upgrade System RAM to 256mb
This one was simple... purchase from seller in the US on eBay. Wait. Open package. Open Quadra 950. Remove old SIMMs. Install. Or so it should have been... quite the initial scare when, upon applying power, the machine didn't start. It powered, the CD-ROM was eject-able, but it just sat there! around 2 minutes later the grey screen came up. It seems that the machine is busy checking the RAM.
Further cold starts took just as long; it seems the RAM checks occur every time you boot after a shutdown.
Now that I've got my RAM in there, it's time to use it with A/UX.
Power Supply Fan
Every now and then, the Quadra would start up and the fan would make terrible noises... It sounded like something was actually stuck in it, but I couldn't see anything. Either way, I managed to take a fin off the fan propeller during an attempt to stop it. I now had to replace it. It's a standard 120mm 12v fan and a replacement was easy to find.
As I pulled off the old fan, I found the cause of the previous noises! There was an unused cable-tie in there. It seems that it had either been sucked in, or someone had shoved it in there. It was not damaged and did not come from inside the power supply. Every now and then it'd make its way close enough to the fan blades to make a racket. Seems that a bump would make it quiet again, but it would've been entirely random!
Either way, the new fan was in place with some adjustments; it was around 10mm shallower. The previous fan was also powered by the socket on the power supply. I grafted the new fan onto the old fans plug. The system is now running 'cool' again and much quieter! I even get a pretty blue light inside the case.
Overclocking your Quadra 950
Lowend Mac has the downlow on this. With the PPC card installed, I could max my oscillator out at 80Mhz. The system would then run the 68040 at 40 MHz and the PPC card at 80 MHz. Note that there may be software incompatibilities once you upgrade. Check out Apple Fool's run-down of incompatibilities here. For further information, check out Mac Crystal Oscillator Speedup History 2.6. Note, you may not be here for the Quadra 950, check out the Apple Fool Machine Specifics page to see the recommended crystal for your machine.
Based on the modification options table at Apple Fool, the Quadra 950 can take option 1 or option 2. Option 1 sounds the easiest whereas option 2 the safest... either way you need a soldering iron and some guts to tinker with your vintage macintoshes logic board.
The oscillators are available on eBay for a few dollars. I purchased mine from a Hong Kong seller. I bought a 5pk just in case. The are a standard-size unit and have 4 pins. The existing components are soldered into the motherboard, so from here on in you're in for a challenge. The best bet is to unsolder the current crystal and solder in a socket. This will allow for easy replacement to the original crystal if problems are encountered.
It might be hard to find an exact socket for the crystal. Jaycar has 14-pin sockets but they have all pins when we only want the four corners. I've modified a full-size socket by pushing through the intermediate pins.
The sockets are a mongrel to manipulate. Firstly, break off the thin end of the pins to be removed. They only bend when you try to force them out, so remove them from the equation. Next, use pliers or find a surface with a suitable space to push the other side of the pin in to. You could use hammer and nail here, with the head of the nail on the pin. Tap them out gently, but be warned, they are in there solidly and will require a bit of work. I used pliers on them, at an angle, and squeezed them out; but not without minor damage to the housing.
Removing the logic board is straight forward. Remove all the cables from the rear, remove any Nubus cards or PDS PPC card installed. Remove the power supply and hard disks/floppies/cd-roms. Disconnect the speaker and the power switch cables. The debug and reset buttons 'pop out' and can hang half out the front of the case during the process (see pictures.) There is then a tab between the memory banks, to the left, that needs to be pushed down. Once down you just need to slide the whole logic board left and it'll fall into your hands.
Once out, heat up your soldering iron. You'll find the 66.6mhz crystal directly above the 68040 CPU. There's four pins on the back that needs to be de-soldered. Your process will either be to (as I did) loosen them one at a time, jimmying the crystal off the board, or the smarter way: use a solder-sucker to remove all solder from the pins and hope that the crystal will just slide out.
Either way, it took me around 10 laps of the pins with a very gentle lever-action in between to remove the crystal. I then soldered my socket in, not doing the cleanest job!
5 minutes later.... I had an 80mhz PowerPC 601 machine~!
Benchmarking MacOS
Speedometer is included with the Newer Technology Disk downloads. The results, pre-clock-chip, are as follows:
After the chipping, the following results were produced:
Yeeeeey! Not only did the bloody thing boot, the speed increased! It seems round ~20% too. Makes sense really... since the previous crystal was 66.6mhz, with the new being 80.0mhz.
SieveAhl is a recommended benchmark application for 68k Macintoshes. This application performs two tests: Sieve and Ahl. Pre-clock-chip results are reported below. The 500 tests executed very quickly. The site has a disclaimer that running the tests on PowerPCs isn't accurate as they use all sorts of emulation layers to execute 68k code. Either way, I have a clean set of figures pre-chipping.
After the chipping the results were as follows:
...there's that ~20% increase again! Winner... the overall OS felt much zippier.
Over-clocking equals over-heating!
Of course, your mileage will always vary when over-clocking anything. Extra speed always leads to extra heat and then compounds into stability issues; the system was clocked at a specific speed by the manufacturer after rigorous quality control. Unless politics/marketing have come in, then higher clock-speeds have proven to be unstable and therefore weren't selected/enabled. Don't be sad that your CPU created a nuclear event, be happy that you had it rocketing along for a few nanoseconds! Of course, try and keep it cool for as long as you can.
It turns out that the 20% speed increase also increased the heat coming from the CPU. After around 30 minutes of running, depending on what I was actually doing, the machine would freeze. This is a very common symptom of overheating and the best method is to air-cool the CPU. The PowerPC PDS Card has a heatsink on it, but it's only passively-cooled. Fitting a fan to this should help keep the temperatures down.
I grabbed a fan from a local PC store that plugs into the standard power cables. It was a little huge for the scenario, but it kept the CPU nice and cool during normal usage. Note that there ain't much clearance in the case with a fan of this size... if you need more than 2 nubus slots then you'll want a smaller fan that fits inside the heat-sink fins.
If you've successfully over-clocked your 68k then fill out the survey at Apple Fool to keep everyone informed. You can see the results of other successful chippers here.