hunter memory board

[David G]

The famous 'hunter' SRAM memory board. SRAM because it can be backed up by a battery when the ZX81 is turned off. SRAM because it'll allow the ZX81 display to use custom hi-resolution graphics (it's most famous use appeared when WRX graphics software became available).

But it's more than a RAM board. It also can use EPROMs or a mix of RAM+EPROM

1982 prices: $29.95 USD in complete kit form supplied with 2K CMOS RAM (board will accept up to 8K). $15 bare board Hunter Electronics

1982 advertisment

The 'complete' hunter board ($30) came with 2K of static RAM (SRAM) chips. With the included lithium battery, this will retain the data in this type of RAM chip when the mains power is off/disconnected

Has a passthrough connector so other RAM packs can attach to it


'hunter' unpopulated memory board with sockets for four memory chips (2K each)

CONFIGURATIONS

Made in America by Paul Hunter they can be used in a few configurations.

1) battery backed static RAM board ... [with] reset switch ...

2) It can also be used as an EPROM board using either 4X 2716 EPROMS or 2X 2732 EPROMS made possible by altering a switchable link on the board or 2X static RAM chips and 2X 2716 EPROMS.

CHIPS
6116 memory chip (16K bits/2K bytes) is 2K x 8 is a 5V CMOS SRAM. The -LP version has reduced standby power suitable for a year or more of backup from a small battery. Cost about $7 each in 1983. Pin-compatible with 2716 EPROM

2716 is the classic 2K Erasable-Programmable ROM (read-only memory), suitable for storing semi-permanent programs, or for replacing the Sinclair ROM (if four are used)

BATTERY BACKUP OPTION
The complete kit had the battery backup.

The way I used the board back then was to plug the Hunter board into the 81 then put the Sinclair pack behind it, load say a utility or what ever and save that to the board for future use which was handy in the days of tape loading ... the battery life of 10 years as stated in the manual was a tad optimistic as I barely managed a year with mine.

The switch on the Hunter has one function only, that is to write protect the ram in the 8-16k area. Without the write protect switch the ram can be corrupted, at power down.

The battery kept the included SRAM chip for 10 months, and 2-1/2 months with 8K of them. You could get the LP version of the 6116 and the battery would last 5 times longer (up to 4 years with 2K)

Photo Gallery on timexsinclair.com

MANUAL
* Issue 5 manual scans
* Issue 5 manual on archive.org

[Moggy]

Nice to see my manual got archived.

My two Hunters, one RAM one EPROM, I still have the original correspondence between Paul Hunter and the customer in the states..

[David G]

actually, it's a different manual, but the same revision (Issue 5). Page 3 is missing in the archive (it's a duplicate of Page 2), but thankfully your post contained the scan

This is great stuff. I remember back in 1983/1984 I was thinking about buying SRAM memory -- after having learned that it allowed custom character sets. I never bought any, because as I recall "it was too expensive". Greg Harder reminded me it wasn't very expensive, and so researching it, i see that now. And back in the day I bought a 32K MemoPak instead. Which was a lot more money. So my thinking at the time must have been the value proposition wasn't there at the time in 1983 ($30 for playing around with the character set?). I never knew it would "save" your work on the built-in battery -- that alone seems worth the money. Later when WRG hi-res came out the SRAM would have worked with it. But I wasn't aware of that. The first hi-res I saw was last month when Greg posted the

SHREB Quickies

If I had seen that back in 1985 my career might have been different. I ended up in the PC industry but not until 1992 and even then only by chance ...

Ironically, I never used more than 16K of 32K pack, i only realized earlier this year ... however the MemoPak was great. I loved the styling and never experienced the RAM-pack wobble that turned many Sinclair users away from the machine

[Moggy]

actually, it's a different manual, but the same revision (Issue 5). Page 3 is missing in the archive (it's a duplicate of Page 2), but thankfully your post contained the scan

.

No this is my manual not a different one. Compare it to the one I posted originally, someone has archived it.

If you check each page side by side you will see all the hand done annotations on my manual are the same as the archived version even the crease/smudge marks on the paper are the same so yes my manual archived with the missing page a fault of the archivist.

One page from the archive and one page of my original post made in 2011 as example.

[David G]

good to know

[David G]

Hardware Review: "8K Non-Volatile Memory Kit" by Peter D. Hoffman from SYNC magazine v3n2 March/April 1983 page 70

Hardware Review

8K Non-Volatile Memory Kit
Peter D. Hoffman

8K Non-Volatile Memory Kit. Hunter, 1630 Forest Hills Dr., Okemos, MI 48864. Complete kit: $29.95 plus shipping; PC board and manual: $15.00.

The Non-Volatile memory (NVM) kit is a battery backup powered RAM board that is primarily designed to fill the transparent address area between 8K and 16K in the Sinclair ZX80/81. The key feature of this product is that with the onboard battery, the routines stored in NVM are retained even with ZX81 power supply unplugged.

The transparent address area is not affected by the Sinclair operating system. Commands such as NEW do not disturb this area. This area is the ideal place to store machine language routines instead of in REM statements, string variables, or above RAMTOP. Thus you can develop your own system utilities, machine language subroutines, alternate display file, etc. Since this is RAM, the routine can be easily modified. For versatility this is even better than an EPROM. The NVM can also be used at any of the 8K blocks between 0K and 32K.

The complete kit comes with instructions, PC board, all components, lithium battery, and one HM611P-3 CMOS static RAM chip. The one chip provides 2K RAM. The space and sockets will accept full complement of four RAM chips. Construction takes a leisurely four hours to complete.

The lithium battery provides 10 months of life with one 2K chip on the board and 2 + months with four of the standard RAM chips. There is available from suppliers (at a premium price) a low power version of the 6116 which uses only 1/5 the power during idle.

The PC board is of very good quality and has several design touches that are nice extra features. A CPU reset pushbutton eliminates unplugging the power when crashes occur. There is a connection provided for a secondary backup battery, such as NiCads, which will further extend the life of the lithium battery. Extensive jumper connections are provided to handle the various options described in the documentation.

The instructions and documentation are strong points in this kit. The documentation is very complete and lucid. There is no trouble in following the construction instructions. The documentation includes parts list, schematic, lots of notes to cover the other options available, such as use of 2716/2732 EPROMs, EPROM/RAM mixture, or use with the ZX80. Finally, a sample program shows the use of a rapid secondary display file and utility programs for saving and reloading the NVM from backup tape.

I did have some initial problems with the contact between the NVM board and the Sinclair 16K RAM pack which piggybacks onto the NVM. The connector board simply needed to be cleaned to remove residual solder flux. Three was also a problem with defective retention of the memory. After much experimentation and modification, I found that this was occurring during the power transients and that the simple expedient of holding down the reset button while plugging/unplugging the 9V power cured the problem.

The edge connector to the computer is a wirewrap style with the wirewrap pins projecting through the NVM PC board to carry the signals to the 16K RAM pack. The small board, to which the 16K RAM pack connects, is placed between the wirewrap pins, the pins are bent inward and soldered to the board. This looks a little strange and awkward at first, but actually makes for a very sturdy assembly. The complete assembly of computer, RAM pack, and NVM makes a firmer connection with less wobble and crash problems than the original.

The ability to have utility routines available without having to do a tape reload at every session is a boon to a machine language programmer. This kit ranks quite high on the list of "must haves" for any serious machine language work.

---------------
Peter D. Hoffman, 5618 Martinique Dr., Corpus Christi, TX 78411.

70 SYNC Magazine

[David G]

The parts list has this: 1 momentary push button switch (Panasonic EVQ-P1R04K). So what about the second switch? Does it use another EVQ-P1R04K?

Per the manual

• Reset switch

• Write-protect switch "The switch can be epoxied to the front of the NVM board opposite the reset switch'

It's not clear but I think the included one switch is the reset switch. It says "Addition of a write-protect switch ... is worthwhile" -- that sounds like the WP switch is an optional thing a user might want to add

Most of the photos I can find show no switch at all. Maybe a lot of users bought the bare board instead of the complete kit

[Moggy]

The write protect switch is shown in the pictures I provided how ever for more clarity some close ups of both switches.
The write protect switch I found is a necessity not something worthwhile , as regardless of what the manual might state, in use without it the stored data corrupts and I suspect I'm not the only one who discovered that.

Also the write protect switch as provided is rather stiff in operation and great care has to be taken when switching as the slightest wobbles ruins everything.