Wednesday, November 20, 2019

The NEC PC-8401 Reexamined: Part 2

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RAM Expansion Cartridges

One of the shortcomings of the NEC PC-8401 is the lack of RAM. By default the computers base 64k is divided in half between file storage and system memory. While 32k is plenty for running the software available in ROM, this limits options when running other software that may require large amounts of memory. Conversely the remaining 32k of RAM dedicated to file storage as a RAM disk places similar constraints on user file and program retention.

Fortunately memory limitations could be alleviated with the addition of RAM expansion cards. These RAM cartridges were to be available in 3 sizes, 128k, 64k and 32k. Rather than adding directly to available application memory, the expansions are used as RAM Disks and must be formatted by the Operating System before use. Once the additional storage is available the PC-8401s base memory may be configured to use the full base 64k as application memory or you may keep existing 32k shared memory split.

No RAM Expansion Attached
32k: Applications RAM
32k: RAM Disk Drive A:

RAM Expanded Machine Option 1
32k: Applications RAM
32k: RAM Disk Drive A:
32/64/128k: RAM Disk Drive B:

RAM Expanded Machine Option 2
64k: Applications RAM
32/64/128k: RAM Disk Drive A:

The PC-8406A 32k RAM Cartridge

The PC-8406A 32k cartridge internals are relatively compact, containing 74 Series logic chips and 16 D446G-15 NEC 2K X 8-BIT SRAM chips mounted on both sides of the circuit board. The SRAM contents are maintained by a CR2032 lithium battery; during battery changes the carts can be powered externally via a 5v barrel jack. Interestingly for the time, just about all the chips contained on the PCB are SMD variants.

The PC-8406A 32k RAM Cartridge.

Unfortunately the PC-8406A 32k pack is on the smaller side of useful, and probably best as a temporary storage device for moving files around. It's not a serious contender as a mass storage device. Even by the file and program sizes of the 1980s it's small. You could for example install MS BASIC on the drive, but then you have very little storage space left for saving programs.

Underside of the PC-8406A 32k RAM Cartridge.

Niggling issues with the NEC PC-8401s overall design choices only increase from there, being that other mass storage devices available of the computer such as the PC-8431A Micro Floppy Disk Unit make no provision for using the RAM carts at the same time, and even the CRT adaptor precludes the usage of the RAM cart as the PC-8401's expansion port provides no means of connecting multiple add-ons.

Effectively there is no easy method of copying the contents of the RAM cart to less volatile floppy disk media. The limitations of the 32k cart apply to a lesser extent to the 64k and 128k expansions, however due to how the PC-8041's memory management works the higher rated cards are inherently more useful as storage mechanisms to begin with.

Severe limitations and all, the RAM carts do help turn the base unit into a more practical computer. Even the 32k cart certainly enhances the PC-8401 user experience, especially in its predicted role as a word processing and spreadsheet powerhouse.

See all entries for this project:  Part 1Part 2

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Sunday, November 17, 2019

ZX81 Game: TuT-TuT - Editions

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What news of the ZX81 version of the TuT-TuT since the initial release you ask? Well there are some exciting developments that need some sharing.

Physical Tape Release of TuT-TuT

I'd mentioned in the previous post that a physical tape release was in the works. Simon Ullyatt and his brilliant retro publishing label Cronosoft will be releasing the game in the not to distant future.

Simon is busy putting the game through some additional testing on real hardware, checking the loading from real tapes and the like. Then of course there is the small matter of cassette production, once all is confirmed the release date will be announced, so stay tuned for exact dates.

Of course what's a physical tape release without some good cover art? After an intense drawing session on my part and some quality layout work on Simon's side of things we have a tape inlay cover ready to go. Those mummies really look menacing, would you dare enter this tomb? (Of course you will)

Coming to a Tape Player near you, the Soon to be released Tape version of TuT-TuT  

UDG 4 ZXpand Edition 

For those fortunate enough to own both a ZXpand and a UDG 4 ZXpand expansion cards for their ZX81s, Moggy from over on the Sinclair ZX World forums created a User Defined Graphics set for TuT-TuT. Don't have the expansion or a ZX81, no need to worry the enhancements can be used with the excellent EightyOne Sinclair Emulator.

All instructions on how to use the UDG version in an Emulator or with a real ZX81, along with the required files are all now included in the TuT-TuT tape file download.

Original ZX81 version and the enhanced UDG 4 ZXpand graphics set.

Get TuTing on an iPhone

In need of a mobile on the go fix of some TuT-TuT action? Kevin Palser has your desires covered if you're an iPhone / IOS user. TuT-TuT is to be included in the next release of the his ZX81 for IOS emulator. The latest version of the emulator should be appearing later this week (Late Nov 20119).

The ZX Spectrum Version

The ZX Spectrum version of TuT-TuT has been a huge success all off it's own. A big thanks for the overwhelmingly positive reviews circulating out there in the wild.

A special shoutout to Ewan Spence for his play through of the game on his Retro Spectrum YouTube channel. It's been great to see so many great reactions to the game. Who would have thought a game written in Spectrum BASIC could be such a hit in 2019.

The Spectrum version of the game was all about challenging the idea that Sinclair BASIC couldn't be used effectively in games creation, I think I've managed to help in some way to bust that myth. If you haven't yet, go grab yourself a copy from Paleotroic Magazine and get playing, remember to check out some of the other articles while there.

The ZX81 Version is more than a Conversion

If you've had fun playing TuT-TuT on the ZX Spectrum be sure to give the ZX81 version a play through.

Unlike the Spectrum TuT-TuT, the ZX81 game is not written in BASIC, this left the door open for some enhancements of gameplay and features. While some of the levels will be familiar, many have been subtly changed and many more added, in fact there are almost twice the amount on the ZX81.

Getting a Copy of TuT-TuT

ZX81 Versions

ZX Spectrum Versions

Love the Game?

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