SY99 8MB Expansion History

How did it come to be? Who did it first?

So the story goes...

The first 8MB expansion was the SY99 Sample-EX produced by Musitronics in ~1993 and long since unavailable.

Manny Fernandez (DrSynth), the motivator behind us producing the MMB, writes:

For me, the quest for maximum sample RAM in my SY99’s goes back to 2016 when I came out of “programming retirement” and rekindled my passion for FM programming. I decided to expand the FM setup from my Yamaha programming days that consisted of an original, fully expanded SY99, a TG77, two DX7II FD’s, a TX802 and a FS1R. It has since mutated into the “FM Rig of DOOM” with the addition of six SY99’s and three TG77’s.

The need to upgrade the additional SY99’s led me to purchasing a number of the SYEMB05 clones, DataBlades & WaveBlades which are great products from Brian over at In searching the WWW for tips on repairing and refurbishing a number of those newly acquired SY99’s I came across “SY99” MarkW’ and his awesome homebuilt upgrades he did for his SY99. It got me thinking about the old Musitronics upgrade for the SY99 that increased the onboard sample RAM to 8MB and thought it would be really cool to have a upgrade solution to max out the SY99.

The Musitronics Expansion was short lived as far as I recall - I have no idea how many were made or sold in total, and over the years it’s become a Unicorn. As the SY99 started to get it’s cult status, I found through the Yamaha UK Forums & Facebook that a number of people were interested in maxing out their SY99’s and had contacted Musitronics over the years to make their expansion again. Lot’s of "we'll consider if there’s enough interest” responses but nothing ever came of it.

There were other obstacles — Having OS/CPU version 1.57 in your SY99 was a necessary requirement. The majority of SY99’s shipped with version 1.40 or earlier, with all chips removable in sockets. The final run did have version 1.57 installed, and had the CPU and OS chips soldered directly on the circuit board. Two important bugs in the prior version of the OS fixed in 1.57 — the ability to actually use all 99 sample Wave locations, and for the SY99 to correctly write the multi-floppy disk saves needed if you have multiple SYEMB05 boards installed. (See this thread on the Yamaha UK Forums.)

After confirming we could make 1.57 version CPU’s, in early 2017 I contacted Musitronics myself, had a few emails with Oliver there, offered payment up front for 5-6 boards, he said he’d get board fab estimates and give me a price for them. Then, I heard nothing — I bugged him for another 2 months or so, never got any further responses from him. So, things not looking good at this point, which brings me to an interesting historical note —

Many of the engineers who created the SY99 also worked on the VL1 project on which I spent a lot of time with them. Because I’ve been #1 SY99 fan from my participation in it’s development voicing (and the SY77) , I was intrigued even then with the Musitronics upgrade. I asked the engineers why they didn’t give the SY99 the full 8MB ability right out of the gate, and their answer IIRC was twofold:

The usual - cost - was the main one. The second was space - they were married to the expansion slot concept. Because of the cost concerns, the expansion slot concept allowed users to add as many or few SYEMB05 boards as they needed/could afford. The chassis accommodated 5 slots easily. No way to make room for another 10 slots! Totally made sense at the time. I was curious as to why a EPROM OS upgrade needed for the Musitronics board to see more memory in contrast to the theYamaha OS. Their answer was the original coding was done strictly to the hardware specification, so only addressed those specified memory ranges. But changing the code to access the additional available memory addresses is a simple edit for them (Yamaha) to do.

Now, during the quest for making new 1.57 CPU’s I was in touch with Toshi Kunimoto, the Yamaha engineering legend, to help out for info on the CPU specs and code mod info. He was able to confirm the HD6475328CP10 CPU would work, and offered help on the code mod ’when engineers not so busy.' He also gave direction to resources for programming the H8/532 series, though that was waaaay over my head.

The next step was a hardware design, and I contacted Mark about helping out on the RAM expansion hardware, and he kindly did an 8MB redesign of his original 3MB board. After his design, I tried to engage the Yamaha engineers for the coding patch, but they were still too involved in other things. That’s when Brian stepped up regarding the OS code, which he figured out. Since there still wasn’t an actual expansion board yet, we could only see that Brian’s modification otherwise functioned normally in all other regards in SY99’s with the 3MB expansion by SYEMB05 boards. I had purchased all the necessary parts and components to prototype Mark’s design, but then the project stalled as I got involved in some Montage projects for Yamaha. That's when you [ed:] stepped in. Until you and I tried Brian's EPROM mods with the MMB prototypes we actually never knew if they worked. But all was good, and the MMB became a reality.

Do you have an SY99 story to share with us?

We'd love to hear from you! Please write us, and with your permission, we'll add your story to the history page.